EP0455878A2 - Centrifugeuse de laboratoire - Google Patents

Centrifugeuse de laboratoire Download PDF

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Publication number
EP0455878A2
EP0455878A2 EP90124344A EP90124344A EP0455878A2 EP 0455878 A2 EP0455878 A2 EP 0455878A2 EP 90124344 A EP90124344 A EP 90124344A EP 90124344 A EP90124344 A EP 90124344A EP 0455878 A2 EP0455878 A2 EP 0455878A2
Authority
EP
European Patent Office
Prior art keywords
unbalance
switching
container
centrifuge according
fluid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90124344A
Other languages
German (de)
English (en)
Other versions
EP0455878A3 (en
Inventor
Stefan Lorbach
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Heraeus Sepatech GmbH
Original Assignee
Heraeus Sepatech GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Heraeus Sepatech GmbH filed Critical Heraeus Sepatech GmbH
Publication of EP0455878A2 publication Critical patent/EP0455878A2/fr
Publication of EP0455878A3 publication Critical patent/EP0455878A3/de
Withdrawn legal-status Critical Current

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Classifications

    • 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 invention relates to a laboratory centrifuge with a drive unit having a motor, with a rotor and with a device for detecting an imbalance occurring when the centrifuge is operated, the device having an unbalance element and a switching element, the unbalance element being in a fixed association with the drive unit stands and, in the event of an imbalance, immediately follows the imbalance movement and executes a relative movement with respect to the switching element, a switching signal being generated after a predetermined threshold value of the relative movement has been exceeded which responds to a control unit which interrupts the power supply to the motor.
  • centrifuges To detect unbalance, devices are used on centrifuges which are based on the principle that a plate (unbalance element) attached to the motor housing of the centrifuge upon deflection due to unbalance, a fixed screw (switching element) located at an adjustable distance is touched and an electrical contact is closed and the drive motor is then braked. In the event that the screw is rigidly attached, it will be bent due to an imbalance when it first contacts the plate and is therefore unusable. In a modified version, the screw is placed on rubber buffers so that it can avoid contact with the plate. Here, however, the screw and the rubber buffer as a spring-mass system can vibrate at certain speeds of the centrifuge and trigger a "false alarm".
  • the bolt deflects from the vertical position and makes electrical contact with a spaced-apart contact plate, as a result of which the motor is braked.
  • the invention has for its object to provide a simple and inexpensive, but safe device for detecting an unbalance in all speed ranges of a centrifuge, which is easy to adjust and not susceptible to interference and at the same time both unbalance movements, which are large deflections of the drive unit, as well as such that affect high acceleration values, can be detected in all spatial directions.
  • this object is achieved in the centrifuge specified at the outset in that the switching element forms, together with the unbalance element, a unit which is fastened to the drive unit, the unbalance element having at least two spaced-apart elements which form a signal transmission path, and that the switching element is a switching fluid arranged in a container, which is freely movable within the space determined by the signal transmission path in an ambient fluid and the transmission path, generating the switching signal, opens and / or closes, the switching Fluid and the surrounding fluid have different specific densities and are not miscible with one another and wherein at least one of the two fluids is a liquid.
  • the unbalance element designed as a signal transmission path
  • the signal transmission path follows all movements of the drive unit and changes its position according to the position of the drive unit.
  • the switching element which has at least one freely movable liquid, which is located in a container that is attached to the drive unit, follows the movements of the drive unit with a delay due to its inert mass or, in the case of very fast movements, does not follow at all and forms due to the heavy mass of the liquid a liquid level regardless of the position of the drive unit or position of the signal transmission path.
  • movements of the drive unit lead to changes in position or relative movements between the signal transmission path and switching element, whereby switching signals can be generated.
  • the switching element is designed as a fluid, deformations of the switching element and misalignments of the unbalance detection device caused thereby are prevented. A coordinated adjustment of the elements of the unbalance detection device is not necessary since the switching element and the unbalance element form a unit.
  • the container In order to prevent loss of the fluids through evaporation or spillage, the container is designed to be closed.
  • the switching fluid is an electrically conductive liquid.
  • the operating state of the imbalance detection device in the idle state is advantageously such that the liquid closes the electrical contact between the electrically conductive components.
  • the opening of the electrical contact during a centrifuge run can be attributed both to a critical deflection of the drive unit from its rest position and to very rapid vibrations of the drive unit, in which the electrically conductive liquid is distributed in the container and the contact thereby opens.
  • An open electrical contact in the idle state of the centrifuge is an indication of an interruption in the electrical line from the control unit to the device.
  • the electrically conductive elements of the unbalance element are pins which protrude into the interior of the container and whose current leads are led through the wall of the container in an electrically insulated manner.
  • the sensitivity of this arrangement is increased if the pins have electrically insulating side walls and only the end faces or the tips of the pins are designed to be electrically conductive.
  • one or both of the electrically conductive elements of the unbalance element is designed as part of the container in which the electrically conductive liquid is located.
  • the container e.g. B. as a rotationally symmetrical component, it is possible to position and design the electrically conductive elements so that they are arranged centrally to one another, which ensures the same sensitivity of the device for deflections of the drive unit from the vertical in all directions.
  • Mercury has proven itself as an electrically conductive liquid.
  • the unbalance detection device which is characterized in that movements of the drive unit caused by unbalance, which do not exceed the predetermined threshold value, can also be detected and evaluated via evaluation electronics for controlling the centrifuge run, the elements of the unbalance element form a light barrier .
  • the fluids that are located within the light barrier have very different light transmissions, with the fluid with the lower light transmission or the fluid with the higher one being in the idle state of the centrifuge Translucency is located inside the light barrier.
  • the container In order to ensure a defined position of the two fluids relative to one another in the idle state, it is advantageous to design the container as a spherical segment, and to arrange it in such a way that the curved outer surface of the container is directed downward when the specific density of the switching fluid is greater than the specific density of the surrounding fluid and the curved outer surface of the container faces upward when the specific gravity of the switching fluid is less than the specific gravity of the surrounding fluid.
  • the quantity, specific density and viscosity of the switching fluid and the geometric arrangement of the imbalance element such that from a tilting of the container from the vertical orientation by more than 10 degrees and / or from an acceleration of the container of more than the simple acceleration due to gravity, the switching signal is generated which leads to the braking of the motor.
  • the amount of switching fluid required for this depends on the internal dimensions of the container and can be determined empirically or mathematically in a simple manner.
  • the desired degree of inertia or agility with which the imbalance detection device reacts to imbalance movements is set via the density and viscosity of the switching fluid.
  • the fulcrum for the imbalance movements that occur in the event of an imbalance is on the motor base.
  • the unbalance detection device By attaching the unbalance detection device to the drive-side end of the motor housing, at a great distance from the fulcrum, the long, effective lever arm at the location of the container enlarges and thus more precisely detects any imbalance movements that occur.
  • two electrically conductive pins 2 are arranged within a cylindrical container 1, which are at different electrical potentials and whose current connections 3 are led out of the bottom of the container 1 through an electrically insulating bushing 16.
  • the switching element has two fluids, the switching fluid 4 consisting of mercury and the ambient fluid 5 consisting of air. In the idle state of the imbalance detection device, the mercury rinses the pins 2 and closes the electrical contact between them.
  • FIG. 2 shows a modified embodiment of the unbalance detection device compared to FIG. 1, which has a cylindrical container 1 with a hemispherical bottom curved outwards.
  • the wall of the container 1 and a metallic pin 17 arranged centrally within the container 1 are at different electrical potentials. In the idle state, the electrical contact between the metallic pin 17 and the container wall is closed by the switching fluid 4, which consists of mercury.
  • the rotationally symmetrical structure of the imbalance detection device has the advantage that deflections of the container 1 from the vertical are detected in all directions with the same accuracy and the same sensitivity.
  • Another embodiment of the imbalance detection device is shown in FIG.
  • the unbalance element consists of an optical transmitter 9 and an optical receiver 10, which are arranged on supports 11 within the container 1 and which form a light barrier. In the idle state, the light barrier is interrupted by the switching fluid 4, a liquid 12 that is impermeable to the light wavelength used.
  • the container 1 is designed in the form of a hollow spherical segment and, when the centrifuge is at rest, its curvature is oriented vertically upward. At its highest point there is an optical transmitter 9 on the outer wall of the container and an optical receiver 10 on the opposite outer wall of the container, the optical transmitter 9 and the optical receiver 10 forming a light barrier.
  • the switching fluid 4 is in the form of a gas bubble 13 which, when the centrifuge is at rest, floating on the surrounding fluid 5, is located within the light barrier and contains a gas which is not absorbing for the light wavelength used.
  • the ambient fluid 5 consists of an oil which is opaque to the light wavelength used.
  • the amount of gas is selected so that in the idle state of the centrifuge the light spot between the transmitter 9 and the receiver 10 fills the gas bubble 13 in its entire width and the maximum light intensity is registered at the receiver 10.
  • the light barrier moves out of the area of the gas bubble 13, the light intensity registered at the receiver 10 decreasing to zero.
  • the radius of curvature of the container 1 and the width of the light spot are chosen so that the light intensity registered at the receiver 10 is zero when the container 1 is tilted by 40 degrees. If the container 1 is tilted from the vertical by less than 40 degrees, light intensities between zero and the maximum are measured, the measured values being able to be used to control the centrifuge run.
  • FIG. 5 to 7 schematically illustrate the mode of operation of the imbalance detection device shown in FIG. 1 for different types of imbalance movements.
  • FIG. 5 shows a tilting of the container 1 from the vertical and the resulting opening of the electrical contact between the electrically conductive pins 2.
  • the opening of the electrical contact is due to a horizontal oscillating movement along the directional arrow of the drive unit 14 designated by the reference number 18 and the container 1 rigidly attached thereto, the switching fluid 4, mercury, being distributed on the wall of the container 1.
  • FIG. 7 shows how, due to the critical vibrations of the drive unit 14 that occur at high speeds of an unbalanced centriguge, the mercury is distributed in droplet form on the wall of the container 1, whereby the electrical contact between the electrically conductive pins 2 is also opened.
  • FIG 8 the arrangement of the imbalance detection device on a plastic carrier 19 is shown, which is arranged on the drive side on the drive unit 14 so that it surrounds the drive shaft 20 of the motor 7 in a cup shape and has mounting surfaces on its side walls on which the imbalance detection -Fitting is fixed oriented. Due to the floating mounting of the drive unit 14 on rubber buffers 15, the pivot point for the movements occurring in the event of imbalance is on the motor base. By attaching the container 1 to the drive end of the motor 7, in a large distance from the fulcrum is achieved by the long, effective lever arm at the location of the container 1, an enlargement and thus a more precise detection of imbalance movements that occur.

Landscapes

  • Centrifugal Separators (AREA)
EP19900124344 1990-05-05 1990-12-15 Laboratory centrifuge Withdrawn EP0455878A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4014446 1990-05-05
DE4014446 1990-05-05

Publications (2)

Publication Number Publication Date
EP0455878A2 true EP0455878A2 (fr) 1991-11-13
EP0455878A3 EP0455878A3 (en) 1992-01-22

Family

ID=6405769

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900124344 Withdrawn EP0455878A3 (en) 1990-05-05 1990-12-15 Laboratory centrifuge

Country Status (1)

Country Link
EP (1) EP0455878A3 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19539633A1 (de) * 1995-10-25 1997-04-30 Heraeus Instr Gmbh Verfahren und Vorrichtung zur Ermittlung einer Unwucht sowie Anwendung der Vorrichtung
DE102004021627B3 (de) * 2004-05-03 2005-08-18 Koenig & Bauer Ag Rollenträger zur Lagerung einer aufgeachsten Vorratsrolle
EP3388810B1 (fr) 2017-04-13 2020-03-11 ebm-papst Mulfingen GmbH & Co. KG Procédé et dispositif de détection de balancement

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4099667A (en) * 1976-07-09 1978-07-11 Kabushiki Kaisha Kubota Seisakusho Apparatus for preventing vibration in a centrifugal separator
GB2072834A (en) * 1980-03-31 1981-10-07 Rolando John Louis Motion sensing apparatus with variable threshold
JPS6117070A (ja) * 1984-07-02 1986-01-25 Nissan Motor Co Ltd 加速度センサ
EP0313444A2 (fr) * 1987-10-22 1989-04-26 JOUAN, Société Anonyme dite Dispositif pour la détection du balourd d'une machine tournante à partir d'un seuil prédéterminé

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4099667A (en) * 1976-07-09 1978-07-11 Kabushiki Kaisha Kubota Seisakusho Apparatus for preventing vibration in a centrifugal separator
GB2072834A (en) * 1980-03-31 1981-10-07 Rolando John Louis Motion sensing apparatus with variable threshold
JPS6117070A (ja) * 1984-07-02 1986-01-25 Nissan Motor Co Ltd 加速度センサ
EP0313444A2 (fr) * 1987-10-22 1989-04-26 JOUAN, Société Anonyme dite Dispositif pour la détection du balourd d'une machine tournante à partir d'un seuil prédéterminé

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 10, no. 160 (P-465)(2216) 7. Juni 1986 & JP-A-61 017 070 ( NISSAN JIDOSHA K.K. ) 25. Januar 1986 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19539633A1 (de) * 1995-10-25 1997-04-30 Heraeus Instr Gmbh Verfahren und Vorrichtung zur Ermittlung einer Unwucht sowie Anwendung der Vorrichtung
DE19539633C2 (de) * 1995-10-25 1998-06-04 Heraeus Instr Gmbh & Co Kg Verfahren zur Ermittlung einer Unwucht eines mittels einer Antriebseinrichtung in Drehung versetzten Rotors einer Zentrifuge und Vorrichtung zur Durchführung des Verfahrens
DE102004021627B3 (de) * 2004-05-03 2005-08-18 Koenig & Bauer Ag Rollenträger zur Lagerung einer aufgeachsten Vorratsrolle
EP3388810B1 (fr) 2017-04-13 2020-03-11 ebm-papst Mulfingen GmbH & Co. KG Procédé et dispositif de détection de balancement

Also Published As

Publication number Publication date
EP0455878A3 (en) 1992-01-22

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