Abstract
A stirring device for wastewater includes a drive device having a drive shaft extending vertically in the assembled state, a stirring body mounted on the drive shaft, a safety bearing in which a free end of the drive shaft is rotatably held, a slide sleeve is mounted on the free end of the drive shaft, and a device for detecting a state of wear of the slide sleeve. The device for detecting the state of wear includes a sensor mounted on the safety bearing and an evaluation device for evaluating the signals delivered by the sensor.
Claims
1. A stirring device for wastewater, comprising a drive device having a drive shaft extending vertically therefrom in an assembled state, a stirring body mounted on the drive shaft, a safety bearing, in which a free end of the drive shaft is rotatably held, a slide sleeve mounted on the free end of the drive shaft, and a device for detecting a state of wear of the slide sleeve, wherein the device for detecting the state of wear comprises a sensor mounted on the safety bearing and an evaluation device for evaluating signals delivered by the sensor, a plurality of permanent magnets detectable by means of the sensor is accommodated in, and distributed over a periphery of, the slide sleeve, and the plurality of permanent magnets is provided in the slide sleeve at different depths from one another with respect to an outer periphery of the slide sleeve.
2. The stirring device according to claim 1, wherein the evaluation device comprises a circuit, which automatically switches off the drive device upon detection of a predefined state of wear of the slide sleeve.
3. The stirring device according to claim 1, wherein the device for detecting the state of wear comprises a display device for displaying an operating state determined by the evaluation device.
4. The stirring device according to claim 3, wherein the operating state is the state of wear of the slide sleeve or an emergency stop state.
5. The stirring device according to claim 1, wherein the safety bearing comprises a bearing bush surrounding the slide sleeve and the sensor is mounted on the bearing bush.
6. The stirring device according to claim 5, wherein the safety bearing comprises a holding device for securing to a base of a wastewater tank and the bearing bush is secured to the holding device detachably.
7. The stirring device according to claim 1, wherein the sensor is a magnetic field sensor, and the magnetic field sensor is a Reed switch or a Hall sensor.
8. The stirring device according to claim 1, wherein the plurality of permanent magnets is distributed uniformly over the periphery of the slide sleeve.
9. The stirring device according to claim 1, wherein the stirring body is formed in a hyperboloid-like manner.
Description
BRIEF DESCRIPTION OF THE DRAWING
(1) FIG. 1 shows a schematic side view of a stirring device,
(2) FIG. 2 shows a perspective view of a safety bearing,
(3) FIG. 3 shows a sectional view according to FIG. 2,
(4) FIG. 4 shows a detailed view of the region A in FIG. 3,
(5) FIG. 5 shows a schematic sectional view of a first detection device,
(6) FIG. 6 shows a first pulse sequence over the angle of rotation,
(7) FIG. 7 shows a second pulse sequence over the angle of rotation,
(8) FIG. 8 shows a third pulse sequence over the angle of rotation,
(9) FIG. 9 shows an evaluation device,
(10) FIG. 10 shows a circuit for automatic shutdown,
(11) FIG. 11 shows a schematic sectional view of a second detection device,
(12) FIG. 12 shows a first strain profile of the bearing bush over the angle of rotation,
(13) FIG. 13 shows a second strain profile of the bearing bush over the angle of rotation, and
(14) FIG. 14 shows a schematic sectional view of a third detection device.
DESCRIPTION OF THE PREFERRED EMBODIMENT
(15) In the case of the stirring device shown in FIG. 1, a drive device 1 is secured above a tank base 2, for example to a bridge 3 spanning a wastewater tank (not shown here). The tank base 2 extends in a horizontal direction. In the shown assembled state, a drive shaft 4 extends in a vertical direction from the drive device 1, and a hyperboloid stirring body 5 is mounted on said drive shaft. A free end of the drive shaft 4 extending from an underside of the hyperboloid stirring body 5 is designated by the reference sign E. A ring line 6 for feeding air into a region beneath the hyperboloid stirring body 5 is provided between the tank base 2 and the hyperboloid stirring body 5. Reference sign 7 designates generally a safety bearing mounted on the tank base 2, in which bearing the free end E of the drive shaft 4 is rotatably held.
(16) FIGS. 2 to 4 show an exemplary embodiment of a safety bearing 7. It comprises a holding device 8, which is formed from a trapezoidal sheet metal. A raised portion 9 of the holding device 8 is supported against the tank base 2 (not shown here) via two limbs 10 extending from said portion. A recess 11 is provided in the raised portion 9, in which recess there is secured a bearing bush 12. The free end E of the drive shaft 4 (not shown here in greater detail) is rotatably held in the bearing bush 12. Reference sign 13 designates a sensor mounted on the bearing bush 12. A slide hush or slide sleeve 14 is provided at the free end E of the drive shaft 4 and can be produced from a plastic or metal. The material forming the slide sleeve 14 advantageously has a lower hardness than a further material forming the bearing bush 12. The bearing bush 12 is usually produced from metal, in particular steel. The slide sleeve 14 is secured by means of a screw 15 or the like mounted on the free end E of the drive shaft 4. A worn slide sleeve 14 can be removed by detaching the screw 15 from the free end E of the drive shaft 4 and can be replaced for a new slide sleeve 14. The slide sleeve 14 is preferably produced from an electrically non-conductive or a non-magnetic material, preferably from a plastic, such as PBT, PTFE, PA 6 G, PA 6, PA 66, PA 12 G, PET, PEEK, POM or the like.
(17) In the slide sleeve 14 shown in FIGS. 3 and 4, detection elements are accommodated, which can be detected by the sensor 13 when they are guided past said sensor in the vicinity thereof. By way of example, the detection elements can be permanent magnets 16. In this case, the slide sleeve 14 is produced for example from a plastic. The permanent magnets 16 can be cast into the plastic.
(18) FIG. 5 shows a schematic sectional view through a first detection device. Four permanent magnets 16 are accommodated in the slide sleeve 14, distributed uniformly over the periphery thereof. The permanent magnets 16 are arranged at different depths in the slide sleeve 14 with respect to an outer periphery A. In the present exemplary embodiment a magnetic field sensor, in particular a Hall sensor, is used as sensor 13.
(19) FIG. 6 shows a first pulse sequence, detected by means of the sensor 13, when all permanent magnets 16 are contained in the slide sleeve 14. Four pulses are provided per revolution of the drive shaft 4.
(20) FIG. 7 shows a second pulse sequence. Here, as a result of wear of the slide sleeve 14, the permanent magnet 16 mounted closest to the outer periphery A has already broken off. In this case there are only three pulses per revolution of the drive shaft 7.
(21) In the third pulse sequence shown in FIG. 8, two permanent magnets 16 have already broken off from the slide sleeve 14 as a result of increasing wear. In this case, only two pulses are generated by the sensor 13 per revolution.
(22) Depending on the pulse number per unit of time or a pulse frequency, it is possible to display a state of wear of the slide sleeve 14 outside the wastewater tank by means of a display device. Furthermore, the drive device 1 can be automatically shut down depending on the pulse frequency in order to avoid damage at the free end E of the drive shaft 4 and/or at the bearing bush 12.
(23) FIGS. 9 and 10 show exemplary embodiments of an evaluation device AW and of a circuit S for automatically shutting down the drive device. In the case of the evaluation device AW shown in FIG. 9, a Hall sensor for example is supplied with a measurement voltage via the terminals 0V and 12V. A sensor signal is detected via the terminal E1. The evaluation device AW is supplied with a mains voltage via the connections A1 and A2, which voltage can be interrupted by a first switch S1. It is possible with a second switch S2 to reset a relay R. A switch position of the relay R is selected by means of the evaluation device AW depending on the pulse frequency.
(24) FIG. 10 shows a circuit S for automatically shutting down a motor M of the drive device 1 (not shown here). Reference sign Q1 designates a contactor, which is opened while switching the relay R from the switch position 11/12 into the switch position 11/14. Reference signs P3 and P4 designate display lamps, which display the switched state of the contactor Q1. By way of example, an acoustic signal means can be provided instead of or additionally to the display lamp P3, with which signal means the automatic shutdown of the drive device can be displayed.
(25) FIG. 11 shows a schematic cross-sectional view through a second detection device. Here, the sensor 13 is a strain or bending sensor. By way of example, it can be a strain gauge, a piezoelectric bending sensor, or the like. With a sensor 13 of this type, deformations or vibrations of the bearing bush 12 can be detected depending on the angle of rotation of the drive shaft 4. With increasing wear of the slide sleeve 14, the deformations or vibrations in the bearing bush 12 increase with the rotation of the drive shaft 4.
(26) FIG. 12 shows a deformation ?l over the angle of rotation when the slide sleeve 14 is not worn or is hardly worn.
(27) FIG. 13 shows the deformation of ?l the bearing bush 12 over the angle of rotation, when the slide sleeve 14 is worn. In this case the amplitudes of the deformation ?l are greater than a predefined limit value ?l.sub.g. When the amplitudes of the deformation ?l exceed the limit value ?l.sub.g, this can be used to generate a stop signal for shutting down the drive device 1.
(28) FIG. 14 shows a schematic sectional view through a third detection device. The slide sleeve 14 is in this case provided with a contact pin 17, which is electrically conductively connected to the drive shaft 4 produced from metal. The slide sleeve 14 is in this case produced from a plastic, for example. Here, a simple electrical contact, which is connected to the bearing bush 12, likewise produced from metal, is used as sensor 13. By means of a simple resistance measurement, a state can be identified in which the contact pin 17 is in contact with the bearing bush 12. A signal of this type can be used likewise to shut down the drive device 1.
LIST OF REFERENCE SIGNS
(29) 1 drive device 2 tank base 3 bridge 4 drive shaft 5 stirring body 6 ring line 7 safety bearing 8 holding device 9 raised portion 10 limb 11 recess 12 bearing bush 13 sensor 14 slide sleeve 15 screw 16 permanent magnet 17 contact pin A outer periphery AW evaluation device A1 A2 connection E free end M motor P3, P4 display lamp Q1 contactor R relay S circuit S1 first switch S2 second switch
