EP0313444A2 - Device for detecting the unbalance of a rotating machine when exceeding a predetermined threshold - Google Patents
Device for detecting the unbalance of a rotating machine when exceeding a predetermined threshold Download PDFInfo
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- EP0313444A2 EP0313444A2 EP88402601A EP88402601A EP0313444A2 EP 0313444 A2 EP0313444 A2 EP 0313444A2 EP 88402601 A EP88402601 A EP 88402601A EP 88402601 A EP88402601 A EP 88402601A EP 0313444 A2 EP0313444 A2 EP 0313444A2
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- unbalance
- pendulum
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- mass
- embedded
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
- B04B—CENTRIFUGES
- B04B9/00—Drives specially designed for centrifuges; Arrangement or disposition of transmission gearing; Suspending or balancing rotary bowls
- B04B9/14—Balancing rotary bowls ; Schrappers
- B04B9/146—Unbalance detection devices
Definitions
- the present invention relates to a device for detecting unbalance in rotating machines, and in particular in centrifuges, from a threshold which is considered to be detrimental to the safety of personnel or to the life of the machine.
- the object of the invention is not to determine the value of the unbalance, nor especially the position of the unbalance on the rotating members of the rotary machine, with a view to providing a corrective action, such as balancing machines can do this.
- the sole aim of the invention is to detect an unbalance threshold which would be detrimental to the machine and to stop the operation of the latter before this threshold has been reached, this detection having to be carried out at the lowest cost.
- the device which it is proposed to make must therefore be simple and inexpensive, and therefore of a lower technological level than the detection devices which could be made with magnetic sensors, accelerometers or optoelectronic means.
- the detection device of FIG. 1 is constituted by a microswitch 10 fixed on the casing 12 of a rotating machine, which rests, by means of an elastic suspension 14 ensuring good damping, on a rigid chassis 16, considered therefore as not being unbalanced.
- the imbalance existing in the rotating assembly 18 of the machine is represented schematically by two weights 20, 22 of slightly different masses and which are fixed to the ends of two radial arms integral with the motor shaft and arranged in the extension of each other.
- the machine casing is subjected to an unbalance, which results in vibrations of the casing in the horizontal plane.
- a fixed stop 24 secured to the chassis 16 and which, when the motor is at rest, is at a predetermined distance from the pallet 26 of the microswitch. As soon as the unbalance component in the direction of the stop 24 becomes equal to said distance, the microswitch is engaged and the operation of the machine is interrupted.
- the microswitch is sensitive only along one axis; it therefore does not take into account the transverse components of movement which are always present during the increase in speed; - due to the dispersion of manufacturing tolerances, each microswitch must be set to the factory position until tripping takes place for the value corresponding to the desired detection threshold; - at each imbalance detection, the pallet of the microswitch is subjected to mechanical forces which cause successive deformations of the pallet and which require frequent adjustments of the microswitch and sometimes even its replacement; - after a certain period of use, the suspensions of the machine degrade and modify the relative positions between the chassis and the microswitch; - detection depends on the horizontal setting of the machine. If, for any reason, the horizontality of the machine varies, the microswitch must be adjusted again.
- the second known detection system is based on the principle of inertia. As shown in Figure 2, it consists of a bulb 28, partially filled with a liquid 30 conductive of electricity and having a high inertia. For this purpose, the bulb has a small volume and a liquid having a high density will be chosen, for example mercury.
- the bulb is fixed integral with the casing 12 of the rotary machine. Its upper wall is crossed by two electrodes 32 which, when the machine is at rest, are not in contact with the mercury. During the movements of the casing, if the unbalance reaches a certain threshold, the mercury establishes a contact between the two electrodes and thus closes an electrical circuit which triggers an alarm or the stopping of the machine.
- This detection device no longer has some of the faults reported for the previous device. Indeed, the detection does not depend on the relative position between the machine housing and the fixed chassis. No mechanical adjustment should be made. Unlike the previous one, this device is not very sensitive to aging. In addition, detection is independent of horizontality.
- the detection is done only along the vertical axis.
- the rotating assembly generates an unbalance having movement components also along two horizontal axes, perpendicular to each other.
- the mercury bulb is unable to detect the unbalance components along said horizontal axes; - It is shown that the detection condition depends on the mass of the mercury and the distance between the surface of the mercury and the end of the electrodes. If the manufacturers can guarantee the precision of the mass, it is not the same with regard to the aforementioned distance for which the desired precision is of the order of a few tenths of a millimeter.
- the present invention aims to remedy the drawbacks of the prior art and therefore proposes an imbalance detection device which does not require adjustment in the factory or in customers, the detection of which is very little dependent on the horizontality, which is insensitive with aging, which has good reproducibility from one device to another, and finally that allows unbalance to be detected along two horizontal axes.
- the detection device is characterized in that it consists of a pendulum formed of a vertical rod, of an elastically deformable metal, the upper end of which is embedded in an insulating support, rigidly attached to the housing.
- the rotary machine and which carries a metal mass at its lower end, the latter being received concentrically and with a predetermined peripheral clearance inside a metal ring, also integral with the casing and electrically insulated from the latter, said ring and said recessed end of the pendulum being electrically connected to an electric alarm or safety circuit which closes as soon as the mass comes into contact with the ring, as a result of the appearance of an unbalance whose horizontal component transmitted to said mass by the rod is equal to the value of said peripheral clearance, the physical characteristics of said pendulum being chosen so that its resonant frequency is lower than that of the parts of the rotating machine subject to unbalance.
- FIGS. 1 and 2 having already been described previously, we will pass directly to the description of FIG. 3.
- the rotating machine shown in this figure is a centrifuge 40, but it goes without saying that this example was chosen only to fix ideas.
- the centrifuge comprises a casing 42 in which is housed the drive motor. It has at its upper part an annular flange 44 by which it rests on the edge of an opening 46 formed in a horizontal wall of a frame 48 assumed to be rigidly secured to the ground and therefore not subject to unbalance.
- the casing crosses the opening coaxially and with a large clearance, so that it is supported only by the flange.
- the rotating assembly of the centrifuge is represented diagrammatically in the form of a shaft 50, provided with two radial arms 52, 54 carrying at their ends two weights 56, 58 whose masses are supposed to be slightly different, the difference of the masses, ⁇ m being the imbalance.
- a U-shaped support 62 On the side wall of the casing 42 is rigidly fixed by its central branch 60, a U-shaped support 62, made of electrically insulating material.
- a vertical rod 66 In the upper branch 64 of said support is embedded the upper end of a vertical rod 66 of an elastically deformable metal, preferably steel.
- the rod is vertical and carries at its lower end a metallic mass 68 of cylindrical shape, but which can have any other geometric shape, for example prismatic or spherical.
- the cylindrical mass 68 is received inside a metal ring 70 of larger section and which is crimped inside an opening drilled through the lower arm 72 of the insulating support.
- a metal ring 70 of larger section When the rotating assembly is at rest, the cylindrical mass is exactly in the axis of the ring, a constant peripheral clearance remaining between it and the ring. This play corresponds to the maximum value ⁇ o which is imposed on the angle of movement of the pendulum, when it starts to vibrate during the increase in speed of the rotating crew.
- the rod 66 and the ring 70 are connected by electrical conductors 74, 76 to an electrical or electronic alarm or security circuit, capable of triggering an alarm or of stopping the operation of the drive motor of the moving assembly. , as soon as the mass comes to touch the ring, that is to say as soon as the vibrations of the pendulum are about to exceed the limit amplitude ⁇ o that one has set.
- the elastic pendulum behaves like a damped mechanical oscillator, the casing being the exciting system and the pendulum being the excited system.
- - ⁇ e is the instantaneous excitation angle communicated by the casing (see figure 3). It is the angle whose casing pivots around its center of gravity G under the action of the unbalance; - ⁇ s is the angle of travel of the pendulum under the effect of this excitation; - ⁇ o is the natural oscillation frequency of the pendulum and - ⁇ is the speed of rotation of the rotating crew.
- the frequency ⁇ o is a constant which only depends on the following parameters: - the coefficient of elasticity of the steel rod, - the length of the steel rod, - the value of the suspended mass.
- the frequency ⁇ o increases with the coefficient of elasticity of the rod and, it decreases with the length of the rod and with the value of the suspended mass.
- the damping at a given frequency ⁇ o depends only on the ratio between a viscous friction term and the elasticity coefficient of the rod, said viscous coefficient term being constituted by the friction of the mass of the pendulum in air and by mechanical losses at the attachment of the pendulum to the insulating support.
- the curve of FIG. 4 also shows that when the mobile assembly turns and there is an imbalance of the rotating masses, it generates an excitation angle ⁇ e whose module
- the rotating crew behaves itself as a second order system with a natural frequency of oscillation. The amplitudes then decrease when the speed of rotation exceeds the value corresponding to said natural frequency.
- the condition under which detection will occur will therefore be A ⁇ e ⁇ ⁇ o (1) - ⁇ o being the maximum amplitude allowed for the pendulum, that is to say the angle of deviation of the pendulum when the mas se 68 is in contact with the ring 70, and - A being the amplification coefficient obtained thanks to the elastic pendulum.
- condition (1) we obtain the complete detection condition:
- the unbalance detection device must be optimized so that the unbalance detection occurs under conditions such that the excitation amplitude ⁇ e (t) never reaches values detrimental to the service life and the operational safety of the rotating machine.
- the device according to the invention does not require any factory or customer adjustment. It is insensitive to aging and allows detection which practically does not depend on the horizontality of the rotating machine. In addition, it can detect an imbalance along two perpendicular horizontal axes.
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Abstract
Description
La présente invention concerne un dispositif de détection du balourd dans les machines tournantes, et notamment dans les centrifugeurs, à partir d'un seuil que l'on considère comme étant préjudiciable à la sécurité du personnel ou à la durée de vie de la machine.The present invention relates to a device for detecting unbalance in rotating machines, and in particular in centrifuges, from a threshold which is considered to be detrimental to the safety of personnel or to the life of the machine.
On précise tout de suite que le but de l'invention n'est pas de déterminer la valeur du balourd, ni surtout la position du balourd sur les organes en rotation de la machine tournante, en vue d'y apporter une action correctrice, comme peuvent le faire les machines à équilibrer. Le but unique de l'invention est de détecter un seuil de balourd qui serait préjudiciable à la machine et d'arrêter le fonctionnement de celle-ci avant que ce seuil ait été atteint, cette détection devant se faire au plus faible coût. Le dispositif que l'on se propose de réaliser devra donc être simple et bon marché, et par conséquent d'un niveau technologique inférieur aux dispositifs de détection que l'on pourrait réaliser avec des capteurs magnétiques, des accéléromètres ou des moyens optoélectroniques.It is immediately clear that the object of the invention is not to determine the value of the unbalance, nor especially the position of the unbalance on the rotating members of the rotary machine, with a view to providing a corrective action, such as balancing machines can do this. The sole aim of the invention is to detect an unbalance threshold which would be detrimental to the machine and to stop the operation of the latter before this threshold has been reached, this detection having to be carried out at the lowest cost. The device which it is proposed to make must therefore be simple and inexpensive, and therefore of a lower technological level than the detection devices which could be made with magnetic sensors, accelerometers or optoelectronic means.
On connaît actuellement deux types de dispositifs permettant de détecter, à très faible coût, un balourd d'équipage tournant, notamment de centrifugeur. Ces dispositifs sont illustrés très schématiquement sur les figures 1 et 2 annexées.Two types of device are currently known which make it possible to detect, at very low cost, an unbalance of a rotating crew, in particular of a centrifuge. These devices are illustrated very schematically in Figures 1 and 2 attached.
Le dispositif de détection de la figure 1 est constitué par un minirupteur 10 fixé sur le carter 12 d'une machine tournante, laquelle repose, par l'intermédiaire d'une suspension élastique 14 assurant un bon amortissement, sur un châssis rigide 16,considéré de ce fait comme n'étant pas soumis au balourd. Le déséquilibre existant dans l'équipage tournant 18 de la machine est représenté schématiquement par deux masselottes 20, 22 de masses légèrement différentes et qui sont fixées aux extrémités de deux bras radiaux solidaires de l'arbre du moteur et disposés dans le prolongement l'un de l'autre. Lors de la rotation de l'équipage tournant, le carter de la machine est soumis à un balourd, ce qui se traduit par des vibrations du carter dans le plan horizontal. Pour détecter ce balourd, il est prévu une butée fixe 24 solidaire du châssis 16 et qui, lorsque le moteur est au repos, se trouve à une distance prédéterminée de la palette 26 du minirupteur. Dès que la composante du balourd dans la direction de la butée 24 devient égale à ladite distance, le minirupteur est enclenché et le fonctionnement de la machine est interrompu.The detection device of FIG. 1 is constituted by a
Un tel dispositif présente cependant plusieurs graves inconvénients :
- tout d'abord, le minirupteur n'est sensible que selon un seul axe ; il ne prend donc pas en compte les composantes transversales de mouvement qui sont toujours présentes lors de la montée en vitesse ;
- du fait de la dispersion des tolérances de fabrication, chaque minirupteur doit être réglé en position en usine jusqu'à ce que le déclenchement ait lieu pour la valeur correspondant au seuil de détection voulu ;
- à chaque détection de balourd, la palette du minirupteur est soumise à des efforts mécaniques qui provoquent des déformations successives de la palette et qui nécessitent de fréquents réglages du minirupteur et parfois même son remplacement ;
- après une certaine durée d'utilisation, les suspensions de la machine se dégradent et modifient les positions relatives entre le châssis et le minirupteur ;
- la détection dépend du calage horizontal de la machine. Si, pour une raison quelconque l'horizontalité de la machine varie, il faut procéder à un nouveau réglage du minirupteur.However, such a device has several serious drawbacks:
- first of all, the microswitch is sensitive only along one axis; it therefore does not take into account the transverse components of movement which are always present during the increase in speed;
- due to the dispersion of manufacturing tolerances, each microswitch must be set to the factory position until tripping takes place for the value corresponding to the desired detection threshold;
- at each imbalance detection, the pallet of the microswitch is subjected to mechanical forces which cause successive deformations of the pallet and which require frequent adjustments of the microswitch and sometimes even its replacement;
- after a certain period of use, the suspensions of the machine degrade and modify the relative positions between the chassis and the microswitch;
- detection depends on the horizontal setting of the machine. If, for any reason, the horizontality of the machine varies, the microswitch must be adjusted again.
Le deuxième système de détection connu est basé sur le principe de l'inertie. Comme le montre la figure 2, il est constitué par une ampoule 28, partiellement remplie d'un liquide 30 conducteur de l'électricité et présentant une forte inertie. A cet effet, l'ampoule a un faible volume et on choisira un liquide ayant une forte densité, par exemple le mercure. L'ampoule est fixée solidairement du carter 12 de la machine tournante. Sa paroi supérieure est traversée par deux électrodes 32 qui, lorsque la machine est au repos, ne sont pas en contact avec le mercure. Lors des mouvements du carter, si le balourd atteint un certain seuil, le mercure établit un contact entre les deux électrodes et ferme ainsi un circuit électrique qui déclenche une alarme ou l'arrêt de la machine.The second known detection system is based on the principle of inertia. As shown in Figure 2, it consists of a
Ce dispositif de détection ne présente plus certains parmi les défauts signalés pour le dispositif précédent. En effet, la détection ne dépend pas de la position relative entre le carter de la machine et le châssis fixe. Aucun réglage mécanique ne doit être réalisé. Contrairement au précédent, ce dispositif est peu sensible au vieillissement. De plus, la détection est indépendante de l'horizontalité.This detection device no longer has some of the faults reported for the previous device. Indeed, the detection does not depend on the relative position between the machine housing and the fixed chassis. No mechanical adjustment should be made. Unlike the previous one, this device is not very sensitive to aging. In addition, detection is independent of horizontality.
Cependant, il présente encore de nombreux défauts :
- Ainsi, la détection ne se fait que selon l'axe vertical. Or, comme on l'a expliqué précédemment,par constitution, l'équipage tournant génère un balourd ayant des composantes de mouvement également selon deux axes horizontaux, perpendiculaires entre eux. L'ampoule à mercure est incapable de détecter les composantes de balourd selon lesdits axes horizontaux ;
- on montre que la condition de détection dépend de la masse du mercure et de la distance entre la surface du mercure et l'extrémité des électrodes. Si les fabricants peuvent garantir la précision de la masse, il n'en est pas de même en ce qui concerne la distance susmentionnée pour laquelle la précision recherchée est de l'ordre de quelques dixièmes de millimètre. Il est difficile de maîtriser cette distance, car elle est fortement influencée par la géométrie de l'ampoule ;
- il peut arriver que le balourd soit acceptable, et que malgré celà, à grande vitesse de rotation, le dispositif détécte un balourd parasite. La raison en est qu'à grande vitesse, le mercure s'émulsionne et vient au contact des électrodes.However, it still has many flaws:
- Thus, the detection is done only along the vertical axis. However, as explained above, by constitution, the rotating assembly generates an unbalance having movement components also along two horizontal axes, perpendicular to each other. The mercury bulb is unable to detect the unbalance components along said horizontal axes;
- It is shown that the detection condition depends on the mass of the mercury and the distance between the surface of the mercury and the end of the electrodes. If the manufacturers can guarantee the precision of the mass, it is not the same with regard to the aforementioned distance for which the desired precision is of the order of a few tenths of a millimeter. It is difficult to control this distance, because it is strongly influenced by the geometry of the bulb;
- it may happen that the unbalance is acceptable, and that despite this, at high speed of rotation, the device detects a parasitic unbalance. The reason is that speed, the mercury emulsifies and comes into contact with the electrodes.
Les brevets FR-A-1357 002, US-A-3 226 016, DE-A-1953201 DE-B-1298 045 et NL-A-7304 620 illustrent des exemples de dispositifs de détection de balourd selon l'un des deux types susmentionnés.The patents FR-A-1357 002, US-A-3 226 016, DE-A-1953201 DE-B-1298 045 and NL-A-7304 620 illustrate examples of imbalance detection devices according to one of the two types mentioned above.
La présente invention a pour but de remédier aux inconvénients de la technique antérieure et propose donc un dispositif de détection de balourd qui ne nécessite pas de réglage en usine ou en clientèle, dont la détection soit très peu dépendante de l'horizontalité, qui soit insensible au vieillissement, qui ait une bonne reproductibilité d'un dispositif à l'autre, et enfin que permette de détecter le balourd selon deux axes horizontaux.The present invention aims to remedy the drawbacks of the prior art and therefore proposes an imbalance detection device which does not require adjustment in the factory or in customers, the detection of which is very little dependent on the horizontality, which is insensitive with aging, which has good reproducibility from one device to another, and finally that allows unbalance to be detected along two horizontal axes.
Le dispositif de détection selon l'invention se caractérise en ce qu'il est constitué par un pendule formé d'une tige verticale, en un métal déformable élastiquement, dont l'extrémité supérieure est encastrée dans un support isolant, rigidemant solidaire du carter de la machine tournante et qui porte à son extrémité inférieure une masse métallique, celle-ci étant reçue concentriquement et avec un jeu périphérique prédéterminé à l'intérieur d'une bague métallique, également solidaire du carter et isolée électriquement par rapport à ce dernier, ladite bague et ladite extrémité encastrée du pendule étant reliées électriquement à un circuit électrique d'alarme ou de sécurité qui se ferme dès que la masse vient en contact avec la bague, par suite de l'apparition d'un balourd dont la composante horizontale transmise à ladite masse par la tige est égale à la valeur dudit jeu périphérique, les caractéristique physiques dudit pendule étant choisies pour que sa fréquence de résonance soit inférieure à celle des parties de la machine tournante soumise au balourd.The detection device according to the invention is characterized in that it consists of a pendulum formed of a vertical rod, of an elastically deformable metal, the upper end of which is embedded in an insulating support, rigidly attached to the housing. the rotary machine and which carries a metal mass at its lower end, the latter being received concentrically and with a predetermined peripheral clearance inside a metal ring, also integral with the casing and electrically insulated from the latter, said ring and said recessed end of the pendulum being electrically connected to an electric alarm or safety circuit which closes as soon as the mass comes into contact with the ring, as a result of the appearance of an unbalance whose horizontal component transmitted to said mass by the rod is equal to the value of said peripheral clearance, the physical characteristics of said pendulum being chosen so that its resonant frequency is lower than that of the parts of the rotating machine subject to unbalance.
L'invention sera mieux comprise à la lecture de la description d'un mode de réalisation particulier faite en regard des dessins annexés dans lesquels:
- la figure 3 montre schématiquement un dispositif de détection selon l'invention, équipant une machine tournante, et et
- la figure 4 représente la courbe de variation de l'amplitude réduite du pendule élastique en fonction de la fréquence réduite de vibration.
- FIG. 3 schematically shows a detection device according to the invention, fitted to a rotary machine, and and
- FIG. 4 represents the variation curve of the reduced amplitude of the elastic pendulum as a function of the reduced frequency of vibration.
Les figures 1 et 2 ayant été déjà décrites précédemment, on passera directement à la description de la figure 3.FIGS. 1 and 2 having already been described previously, we will pass directly to the description of FIG. 3.
La machine tournante représentée sur cette figure est un centrifugeur 40, mais il va de soi que cet exemple n'a été choisi que pour fixer les idées. Le centrifugeur comprend un carter 42 dans lequel est logé le moteur d'entraînement. Il comporte à sa partie supérieure une bride annulaire 44 par laquelle il repose sur le bord d'une ouverture 46 formée dans une paroi horizontale d'un châssis 48 supposé être rigidement solidaire du sol et donc non soumis au balourd. Le carter traverse l'ouverture coaxialement et avec un jeu important, de sorte qu'il n'est supporté que par la bride. Un joint périphérique élastique 47 ou plusieurs plots élastiques uniformément répartis le long de la périphérie de la bride, assure l'amortissement de la composante verticale des vibrations dues au balourd dont le carter est le siège.The rotating machine shown in this figure is a
L'équipage tournant du centrifugeur est représenté schématiquement sous forme d'un arbre 50, muni de deux bras radiaux 52, 54 portant à leurs extrémités deux masselottes 56, 58 dont les masses sont supposées être légèrement différentes, la différence des masses, Δm étant le balourd.The rotating assembly of the centrifuge is represented diagrammatically in the form of a
Sur la paroi latérale du carter 42 est rigidement fixé par sa branche centrale 60, un support 62 en forme de U, réalisé en matière électriquement isolante. Dans la branche supérieure 64 dudit support est encastrée l'extrémité supérieure d'une tige verticale 66 en un métal déformable élastiquement, de préférence en acier. La tige est verticale et porte à son extrémité inférieure une masse métallique 68 de forme cylindrique, mais qui peut avoir toute autre forme géométrique, par exemple prismatique ou sphérique.On the side wall of the
La masse cylindrique 68 est reçue à l'intérieur d'une bague métallique 70 de plus grande section et qui est sertie à l'intérieur d'une ouverture percée à travers le bras inférieur 72 du support isolant.Lorsque l'équipage tournant est au repos, la masse cylindrique se trouve exactement dans l'axe de la bague, un jeu périphérique constant subsistant entre elle et la bague. Ce jeu correspond à la valeur maximale φo que l'on impose à l'angle de débattement du pendule, lorsqu'il se met à vibrer pendant la montée en vitesse de l'équipage tournant.The
La tige 66 et la bague 70 sont reliées par des conducteurs électriques 74, 76 à un circuit électrique ou électronique d'alarme ou de sécurité, susceptible de déclencher une alarme ou d'arrêter le fonctionnement du moteur d'entraînement de l'équipage mobile, dès que la masse vient toucher la bague, c'est-à-dire dès que les vibrations du pendule sont sur le point de dépasser l'amplitude limite φo que l'on s'est fixée.The
Pour comprendre le fonctionnement du dispositif de détection de balourd selon l'invention, on expliquera le principe physique sur lequel il repose.To understand the operation of the imbalance detection device according to the invention, the physical principle on which it is based will be explained.
Le pendule élastique se comporte comme un oscillateur mécanique amorti, le carter étant le système excitant et le pendule étant le système excité. On sait qu'un tel oscillateur est régi par une équation différentielle du second ordre et que sa courbe de réponse en fréquence (amplitude réduite en fonction de la fréquence réduite 
- ϑe est l'angle instantané d'excitation communiqué par le carter (voir figure 3). C'est l'angle dont le carter pivote autour de son centre de gravité G sous l'action du balourd ;
- ϑs est l'angle de débattement du pendule sous l'effet de cette excitation ;
- ωo est la fréquence d'oscillation naturelle du pendule et
- ω est la vitesse de rotation de l'équipage tournant.The elastic pendulum behaves like a damped mechanical oscillator, the casing being the exciting system and the pendulum being the excited system. We know that such an oscillator is governed by a second order differential equation and that its frequency response curve (amplitude reduced as a function of the reduced frequency
- ϑ e is the instantaneous excitation angle communicated by the casing (see figure 3). It is the angle whose casing pivots around its center of gravity G under the action of the unbalance;
- ϑ s is the angle of travel of the pendulum under the effect of this excitation;
- ω o is the natural oscillation frequency of the pendulum and
- ω is the speed of rotation of the rotating crew.
La fréquence ωo est une constante qui ne dépend que des paramètres suivants :
- le coefficient d'élasticité de la tige d'acier,
- la longeur de la tige d'acier,
- la valeur de la masse suspendue.The frequency ω o is a constant which only depends on the following parameters:
- the coefficient of elasticity of the steel rod,
- the length of the steel rod,
- the value of the suspended mass.
La fréquence ωo croît avec le coefficient d'élasticité de la tige et, il décroît avec la longueur de la tige et avec la valeur de la masse suspendue.The frequency ω o increases with the coefficient of elasticity of the rod and, it decreases with the length of the rod and with the value of the suspended mass.
L'amortissement à une fréquence ωo donnée ne dépend que du rapport entre un terme de frottement visqueux et le coefficient d'élasticité de la tige, ledit terme de coefficient visqueux étant constitué par les frottements de la masse du pendule dans l'air et par les pertes mécaniques au niveau de la fixation du pendule sur le support isolant.The damping at a given frequency ω o depends only on the ratio between a viscous friction term and the elasticity coefficient of the rod, said viscous coefficient term being constituted by the friction of the mass of the pendulum in air and by mechanical losses at the attachment of the pendulum to the insulating support.
On constate sur la figure 4 que pour une fréquence d'excitation ω du pendule voisine de la fréquence d'oscillation naturelle ωo (donc lorsque 
|ϑs|=A|ϑe|
- A étant le coefficient d'amplification qui ne dépend que du paramètre d'amortissement.It can be seen in FIG. 4 that for an excitation frequency ω of the pendulum close to the natural oscillation frequency ω o (therefore when
| ϑ s | = A | ϑ e |
- A being the amplification coefficient which only depends on the damping parameter.
La courbe de la figure 4 montre encore que lorsque l'équipage mobile tourne et qu'il y a un déséquilibrage des masses tournantes, il génère un angle d'excitation ϑe dont le module |ϑe| croît d'abord avec la vitesse de rotation ω de cet équipage mobile (partie montante de la courbe),du fait de la liaison élastique entre le carter le châssis rigide. L'équipage tournant se comporte lui-même comme un système du deuxième ordre avec une fréquence naturelle d'oscillation. Les amplitudes diminuent ensuite lorsque la vitesse de rotation dépasse la valeur correspondant à ladite fréquence naturelle.The curve of FIG. 4 also shows that when the mobile assembly turns and there is an imbalance of the rotating masses, it generates an excitation angle ϑ e whose module | ϑ e | first increases with the speed of rotation ω of this moving part (rising part of the curve), due to the elastic connection between the casing and the rigid chassis. The rotating crew behaves itself as a second order system with a natural frequency of oscillation. The amplitudes then decrease when the speed of rotation exceeds the value corresponding to said natural frequency.
La condition à laquelle la détection se produira sera donc
Aϑe≧φo (1)
- φo étant l'amplitude maximale permise pour le pendule, c'est-à-dire l'angle de déviation du pendule lorsque la mas se 68 est au contact de la bague 70, et
- A étant le coefficient d'amplification obtenu grâce au pendule élastique.The condition under which detection will occur will therefore be
Aϑ e ≧ φ o (1)
- φ o being the maximum amplitude allowed for the pendulum, that is to say the angle of deviation of the pendulum when the mas se 68 is in contact with the
- A being the amplification coefficient obtained thanks to the elastic pendulum.
On montre que l'amplitude de l'excitation |ϑe| répond à l'équation :
Δm est le balourd
ω est la vitesse de rotation de l'équipage tournant
R est le rayon de giration du balourd
K est un coefficient qui dépend de l'élasticité des suspensions et de la géométrie de l'équipage mobile.We show that the amplitude of the excitation | ϑ e | answers the equation:
Δm is the unbalance
ω is the rotational speed of the rotating crew
R is the unbalance radius of gyration
K is a coefficient which depends on the elasticity of the suspensions and the geometry of the moving assembly.
En tenant compte de la condition (1) on obtient la condition complète de détection :
Le dispositif de détection de balourd selon l'invention doit être optimisé pour que la détection du balourd se produise dans des conditions telles que l'amplitude d'excitation ϑe (t) n'atteigne jamais des valeurs préjudiciables à la durée de vie et à la sécurité de fonctionnement de la machine tournante.The unbalance detection device according to the invention must be optimized so that the unbalance detection occurs under conditions such that the excitation amplitude ϑ e (t) never reaches values detrimental to the service life and the operational safety of the rotating machine.
Il résulte de l'équation (3) que la détection doit s'effectuer à très basse vitesse, afin que si le balourd Δ m dépasse la condition limite, la masse suspendue 68 entre en contact avec la bague 70. En se fermant le circuit électrique génère une commande d'arrêt du moteur et un signal d'alarme pour l'opérateur de la machine.It follows from equation (3) that the detection must be carried out at very low speed, so that if the unbalance Δ m exceeds the limit condition, the suspended
Le dispositif selon l'invention ne nécessite aucun réglage en usine ou en clientèle. Il est insensible au vieillissement et permet d'effectuer une détection qui ne dépend pratiquement pas de l'horizontalité de la machine tournante. De plus, il permet de détecter un balourd selon deux axes horizontaux perpendiculaires.The device according to the invention does not require any factory or customer adjustment. It is insensitive to aging and allows detection which practically does not depend on the horizontality of the rotating machine. In addition, it can detect an imbalance along two perpendicular horizontal axes.
Claims (2)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8714612A FR2622290B1 (en) | 1987-10-22 | 1987-10-22 | DEVICE FOR DETECTING THE BALANCE OF A ROTATING MACHINE FROM A PREDETERMINED THRESHOLD |
| FR8714612 | 1987-10-22 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0313444A2 true EP0313444A2 (en) | 1989-04-26 |
| EP0313444A3 EP0313444A3 (en) | 1990-10-03 |
Family
ID=9356073
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19880402601 Withdrawn EP0313444A3 (en) | 1987-10-22 | 1988-10-13 | Device for detecting the unbalance of a rotating machine when exceeding a predetermined threshold |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4910502A (en) |
| EP (1) | EP0313444A3 (en) |
| FR (1) | FR2622290B1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0455878A2 (en) * | 1990-05-05 | 1991-11-13 | Heraeus Sepatech GmbH | Laboratory centrifuge |
| DE102004049100B4 (en) | 2003-10-09 | 2020-04-23 | Koki Holdings Co., Ltd. | centrifuge |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5415026A (en) * | 1992-02-27 | 1995-05-16 | Ford; David | Vibration warning device including mercury wetted reed gauge switches |
| US5375282A (en) * | 1993-09-20 | 1994-12-27 | General Electric Company | System and method for detecting and interrupting an out-of-balance condition in a washing machine |
| US5375437A (en) * | 1993-09-20 | 1994-12-27 | General Electric Company | Out-of-balance condition detecting system with lid actuated switching assembly |
| DE4335119C2 (en) * | 1993-10-15 | 1997-11-20 | Eppendorf Geraetebau Gmbh | Laboratory centrifuge with unbalance shutdown |
| US5685038A (en) * | 1995-05-18 | 1997-11-11 | U.S. Controls Corporation | Out-of-balance control for washing machine |
| JP3710001B2 (en) * | 1995-06-16 | 2005-10-26 | 日立工機株式会社 | centrifuge |
| KR100274470B1 (en) * | 1997-05-20 | 2000-12-15 | 구자홍 | A method of detecting eccentricity in washing machine and control apparatus thereof |
| CA2242994C (en) * | 1997-07-14 | 2008-09-16 | Lg Electronics Inc. | Method for detecting cloth amount in drum washing machine |
| SE512770C2 (en) * | 1998-02-19 | 2000-05-08 | Alfa Laval Ab | support device |
| US6354988B1 (en) * | 1999-06-17 | 2002-03-12 | Kendro Laboratory Products, Llp | Centrifuge gyro diaphragm capable of maintaining motor shaft concentricity |
| US6422047B1 (en) | 2000-05-04 | 2002-07-23 | Maytag Corporation | Washing machine with unbalance detection and control system |
| US6350224B1 (en) * | 2000-07-17 | 2002-02-26 | Westinghouse Savannah River Company, Llc | Centrifugal unbalance detection system |
| US6635007B2 (en) * | 2000-07-17 | 2003-10-21 | Thermo Iec, Inc. | Method and apparatus for detecting and controlling imbalance conditions in a centrifuge system |
| DE10125808A1 (en) * | 2001-05-26 | 2002-12-12 | Westfalia Separator Food Tec G | centrifugal |
| US20040071569A1 (en) * | 2002-08-02 | 2004-04-15 | Ellsworth James R. | Decanting centrifuge with vibration isolation |
| JP5263570B2 (en) * | 2007-10-31 | 2013-08-14 | 日立工機株式会社 | Centrifuge |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1256550A (en) * | 1960-02-05 | 1961-03-24 | Safety devices for centrifugal machines and the like | |
| US3053949A (en) * | 1959-11-18 | 1962-09-11 | Harold K Johnson | Intermittent electrical switch |
| US3790727A (en) * | 1972-12-13 | 1974-02-05 | Sealectro Corp | Inertia switch with resilient conductive support arm immersed in silicone base viscous fluid medium |
| GB2119574A (en) * | 1982-04-28 | 1983-11-16 | Sentrol Systems Ltd | Detection device |
| US4455461A (en) * | 1982-09-29 | 1984-06-19 | E. I. Dupont De Nemours And Company | Adjustable imbalance detector for a centrifuge |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2081604A (en) * | 1935-02-01 | 1937-05-25 | Fletcher Works Inc | Centrifugal circuit breaker |
| US2807950A (en) * | 1951-09-14 | 1957-10-01 | Borg Warner | Gyration suppression control device for a washing machine |
| DE1298045B (en) * | 1962-04-03 | 1969-06-19 | Goedecker B J Maschf | Device on centrifugal drums to compensate for the imbalance |
| US3226016A (en) * | 1962-07-09 | 1965-12-28 | Monsanto Chem Australia Ltd | Industrial centrifuges |
| FR1357002A (en) * | 1963-02-18 | 1964-04-03 | Hotchkiss Brandt | Safety device for automatic or semi-automatic washing machine |
| US3209561A (en) * | 1963-11-21 | 1965-10-05 | Westinghouse Electric Corp | Unbalance control for washing machines |
| US3227835A (en) * | 1964-10-06 | 1966-01-04 | Borg Warner | Combination out-of-balance and safety spin switch |
| US3583182A (en) * | 1968-10-23 | 1971-06-08 | Hitachi Ltd | Washing machine |
| NL7304620A (en) * | 1973-04-03 | 1974-10-07 | Imbalance cutout switch for rotating bodies - of compact design and assembled close to the objective |
-
1987
- 1987-10-22 FR FR8714612A patent/FR2622290B1/en not_active Expired - Lifetime
-
1988
- 1988-10-13 EP EP19880402601 patent/EP0313444A3/en not_active Withdrawn
- 1988-10-18 US US07/259,172 patent/US4910502A/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3053949A (en) * | 1959-11-18 | 1962-09-11 | Harold K Johnson | Intermittent electrical switch |
| FR1256550A (en) * | 1960-02-05 | 1961-03-24 | Safety devices for centrifugal machines and the like | |
| US3790727A (en) * | 1972-12-13 | 1974-02-05 | Sealectro Corp | Inertia switch with resilient conductive support arm immersed in silicone base viscous fluid medium |
| GB2119574A (en) * | 1982-04-28 | 1983-11-16 | Sentrol Systems Ltd | Detection device |
| US4455461A (en) * | 1982-09-29 | 1984-06-19 | E. I. Dupont De Nemours And Company | Adjustable imbalance detector for a centrifuge |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0455878A2 (en) * | 1990-05-05 | 1991-11-13 | Heraeus Sepatech GmbH | Laboratory centrifuge |
| EP0455878A3 (en) * | 1990-05-05 | 1992-01-22 | Heraeus Sepatech Gmbh | Laboratory centrifuge |
| DE102004049100B4 (en) | 2003-10-09 | 2020-04-23 | Koki Holdings Co., Ltd. | centrifuge |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2622290B1 (en) | 1990-03-30 |
| FR2622290A1 (en) | 1989-04-28 |
| EP0313444A3 (en) | 1990-10-03 |
| US4910502A (en) | 1990-03-20 |
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