Laboratory mill

Abstract

The invention relates to a laboratory mill comprising at least one counter-vibration device (27) which has at least one control unit (29a) for providing a counter-vibration signal (29b) and at least one controllable vibration generation unit (29) for converting the counter-vibration signal (29b) into counter-vibrations (30), wherein the vibration-generation unit (29) counteracts a device- and/or housing part (31) of the laboratory mill (1) and the counter-vibrations (30) lead to an active reduction in the vibrations of the device- and/or housing part (31) and/or an at least partial suppression of noise-inducing vibrations of the device- and/or housing part (31), by means of destructive interference.

Claims

1. A laboratory mill comprising: at least one counter-vibration apparatus having at least one control unit for providing a counter-vibration signal and at least one actuable vibration-generation unit for converting the counter-vibration signal into counter-vibrations; wherein the vibration-generation unit acts counter to at least one of a housing lid enclosing a milling chamber and a housing of the laboratory mill; wherein, by the counter-vibrations, vibrations of the at least one of a housing lid enclosing a milling chamber and a housing of the laboratory mill are actively reduced or vibrations of the at least one of a housing lid enclosing a milling chamber and a housing of the laboratory mill that generate disruptive sound are eliminated at least in part by destructive interference; and wherein the housing of the laboratory mill is configured to be mounted on a base.

2. The laboratory mill according to claim 1, wherein the counter-vibration apparatus is configured to excite the housing of the laboratory mill and housing lid enclosing a milling chamber in phase opposition in a manner coordinated with one another.

3. The laboratory mill according to claim 1, wherein the vibration-generation unit is a piezoelectric actuator or an electromechanical actuator that is placed on the at least one of a housing lid enclosing a milling chamber and a housing of the laboratory mill or that interacts with the at least one of a housing lid enclosing a milling chamber and a housing of the laboratory mill.

4. The laboratory mill according to claim 1, wherein the vibration-generation unit is integrated in a wall of the at least one of a housing lid enclosing a milling chamber and a housing of the laboratory mill.

5. The laboratory mill according to claim 1, wherein at least one sensor is provided for detecting vibrations that generate disruptive sound or for detecting disruptive sound and generating a vibration signal, the control unit being configured to generate the counter-vibration signal by evaluating the vibration signal.

6. The laboratory mill according to claim 1, wherein the vibration-generation unit can be releasably connected to the at least one of a housing lid enclosing a milling chamber and a housing of the laboratory mill or can be attached to different devices or housing parts of the laboratory mill as necessary.

7. The laboratory mill according to claim 1, wherein the control unit comprises at least one adjustment member for manually generating a counter-vibration signal or modifying at least one of a phase position and amplitude of the counter-vibrations.

8. The laboratory mill according to claim 1, wherein at least one sensor is provided for detecting an operational parameter of the laboratory mill, and wherein the control unit provides the counter-vibration signal depending on the detected operational parameter of the laboratory mill.

9. A laboratory mill, comprising: at least one counter-vibration apparatus having at least one control unit for providing a counter-vibration signal and at least one actuable vibration-generation unit for converting the counter-vibration signal into counter-vibrations; wherein the vibration-generation unit acts counter to at least one of a feed funnel and a device stand of the laboratory mill; wherein, by the counter-vibrations, vibrations of the at least one of a feed funnel and a device stand are actively reduced or vibrations of the at least one of a feed funnel and a device stand of the laboratory mill that generate disruptive sound are eliminated at least in part by destructive interference; and wherein the vibration-generation unit is designed and arranged to actively excite the at least one of a feed funnel and a device stand of the laboratory mill in phase opposition.

10. The laboratory mill according to claim 9, wherein the vibration-generation unit is a piezoelectric actuator or an electromechanical actuator that is placed on the at least one of a feed funnel and a device stand of the laboratory mill or interacts with the at least one of a feed funnel and a device stand of the laboratory mill.

11. The laboratory mill according to claim 9, wherein at least one sensor is provided for detecting vibrations that generate disruptive sound or for detecting disruptive sound and generating a vibration signal, the control unit being configured to generate the counter-vibration signal by evaluating the vibration signal.

12. The laboratory mill according to claim 9, wherein the vibration-generation unit can be releasably connected to the at least one of a feed funnel and a device stand of the laboratory mill or can be attached to different devices or housing parts of the laboratory mill as necessary.

13. The laboratory mill according to claim 9, wherein the control unit comprises at least one adjustment member for manually generating a counter-vibration signal or modifying at least one of a phase position and amplitude of the counter-vibrations.

14. The laboratory mill according to claim 9, wherein at least one sensor is provided for detecting an operational parameter of the laboratory mill, and wherein the control unit provides the counter-vibration signal depending on the detected operational parameter of the laboratory mill.

15. A laboratory mill, comprising: at least one counter-sound apparatus having a control unit for providing a counter-sound signal and at least one actuable sound-generation unit for converting the counter-sound signal into counter-sound to actively reduce sound or eliminate disruptive sound at least in part by means of destructive interference; and wherein the sound-generation unit is arranged on or interacts with another device or housing part directly or indirectly adjacent to a sound-emitting device or housing part.

16. The laboratory mill according to claim 15, wherein the sound-generation unit is a piezoelectric actuator, a piezoelectric film, or a speaker that generates a counter-sound field according to its actuation.

17. The laboratory mill according to claim 15, wherein the sound-generation unit is an electromechanical actuator that interacts with the at least one of a device and a housing part capable of vibrating, the at least one of a device and a housing part being made to vibrate by displacements of the actuator and generating a counter-sound field as a result.

18. The laboratory mill according to claim 15, wherein at least one sound sensor is provided for converting disruptive sound into an interference signal, the control unit being configured to generate the counter-sound signal by analyzing the interference signal.

Description

(1) In the drawings:

(2) FIG. 1 is a sectional view of a centrifugal mill showing possible positions for a counter-sound system,

(3) FIG. 2 is a schematic view of a counter-sound apparatus for active sound reduction and/or at least partly eliminating disruptive sound,

(4) FIG. 3 is a schematic view of a counter-vibration apparatus for actively reducing the vibrations from a device and/or housing part emitting disruptive sound and for at least partly eliminating the vibrations generating disruptive sound,

(5) FIG. 4 shows the centrifugal mill shown in FIG. 1, showing possible locations for a counter-vibration system,

(6) FIG. 5 shows a first embodiment of a separate feed funnel for use in a comminution machine for laboratory operation, possible locations for a counter-vibration system on the funnel being shown schematically,

(7) FIG. 6 shows another embodiment of a funnel for a comminution machine,

(8) FIG. 7 is a partially sectional view of the funnel from FIG. 6 inserted into the milling stock tube of a centrifugal mill, and

(9) FIG. 8 is a schematic sectional view of a laboratory mill having a separate funnel arranged above a milling stock funnel of the laboratory mill.

(10) By way of example, FIG. 1 shows the structural design of a laboratory mill 1 in the form of a rotor mill or centrifugal mill. However, the aspects described below also apply to other laboratory mills having a different structural design, in particular to conical mills.

(11) The laboratory mill 1 comprises a rotor 3 coupled to a drive shaft 2 and acting as a milling tool, a milling chamber 4, in which the rotor 3 rotates during a milling process, being surrounded by an annular sieve 5. On the outer circumference of the annular sieve 5, an annular collection container 6 for comminuted milling stock is arranged. The collection container 6 can be closed by a removable container lid 7.

(12) The milling stock is fed into the milling chamber 4 through a milling stock tube 8, which is in fluid communication with a milling stock inlet opening 9. The milling stock is fed into the milling chamber 4 through the milling stock inlet opening 9. During operation of the comminution machine 1, the milling stock tube 8 can be open to the surroundings. This ensures the milling stock is fed into the milling chamber 4 gradually during the milling operation.

(13) In the embodiment shown by way of example, the milling stock tube 8 is defined by a funnel-like wall portion 10 of a housing lid 11 of the laboratory mill 1. The housing lid 11 encloses the milling chamber 4. To further encase the laboratory mill 1, a housing 12 is also provided, which can also be formed in multiple parts and encloses a drive of the laboratory mill 1. The housing lid 11 and the housing 12 form an enclosure or envelope for the laboratory mill 1. The housing 12 rests on a base by means of a base plate 13. The base plate 13 forms part of the device stand for the comminution machine 1.

(14) During milling operation, as a result of the high speeds of centrifugal mills, the laboratory mill 1 produces sound emissions, which are transmitted as airborne and/or structure-borne sound. These signals coupled to the speed of the rotor 3 are very irritating due to the generally high rotational speeds in laboratory use. In conical mills, however, periodic sound emissions occur particularly due to periodic impacts produced by the comminution process. Sound emissions can be produced by the comminution procedure itself, or by a developing air flow that is interrupted cyclically by the periodic comminution procedure.

(15) Airborne sound is then emitted from the milling chamber 4 and into the surrounding area through the milling stock tube 8. If the milling stock tube 8 is open during the milling operation in order to gradually feed the milling stock into the milling chamber 4, there is a continuous airborne-sound path between the emission source in the region of the milling tool and the area surrounding the comminution machine 1. In addition, structure-borne sound emissions occur, which are caused by device and/or housing parts of the comminution machine 1 shaking and vibrating and emanate from the milling chamber 4. These device and/or housing parts can make ambient air vibrate and thus generate airborne sound themselves, and/or strengthen airborne sound emissions through the milling stock tube 8. In addition, vibrating device parts and/or housing parts in turn make adjacent device and/or housing parts vibrate, resulting in the adjacent device parts also potentially emitting airborne sound.

(16) To reduce sound emissions, at least one counter-sound apparatus 14 shown schematically in FIG. 2 can be provided. Said apparatus comprises a control unit 15 for providing a counter-sound signal 16 and at least one actuable sound-generation unit 17, which is shown schematically in FIG. 2 as a speaker. However, the sound-generation unit 17 can also be a piezoelectric actuator, in particular a piezoelectric film. Alternatively to a piezoelectric film, piezoceramic disc elements can also be used. Depending on the actuation, the sound-generation unit 17 generates a counter-sound field 18 for active sound reduction and/or for at least partly eliminating a disruptive-sound field 19 that emanates from the milling chamber 4 and is generated by the rotating milling tool during the comminution process.

(17) As is also clear from FIG. 2, the amplitude and frequency of counter-sound waves 20 generated by the sound-generation unit 17 can substantially correspond to the disruptive-sound waves 21 emanating from the milling chamber 4, although said counter-sound waves are phase-shifted relative to the disruptive-sound waves by preferably 180. Even if the entire spectrum of the undesired sound cannot be eliminated, at least a significant reduction in sound emissions can still be achieved. FIG. 2 schematically shows that the disruptive-sound field 19 can be almost entirely eliminated as a result of the counter-sound field 18.

(18) The disruptive-sound field 19 emanating from the milling chamber 4 is measured by a microphone 22. The microphone 22 converts the disruptive sound into an interference signal 23, the control unit 15 evaluating the interference signal 23 and generating a counter-sound signal 16 on the basis of the evaluation.

(19) Moreover, a second microphone 24 can be provided to act as an error microphone and transmit an error signal 25 to the control unit 15 if the disruptive sound should not be completely eliminated. This creates a feedback loop system in order to completely eliminate disruptive sound as far as possible. In this case, the control unit 15 is in the form of a closed-loop controller. In principle, however, simple open-loop control on the basis of irritating sound waves 21 incident on the microphone 22 can also be provided for the counter-sound generation. In addition, it is also possible to configure the control unit 15 such that the counter-sound signal 16 can be selected from a number of counter-sound signal profiles available in a memory unit (not shown).

(20) In FIG. 1, options for the spatial arrangement of a counter-sound apparatus 14 on the laboratory mill 1 are shown schematically and are marked by X.

(21) As is clear from FIG. 1, a counter-sound apparatus 14 can be provided, for example, in the region of a device and/or housing part that indirectly or directly encloses the milling chamber 4. The sound-generation unit 17 or an electroacoustic and/or electromechanical actuator can be arranged on the collection container 6, in particular on the outer wall thereof. An electroacoustic and/or electromechanical actuator can also be integrated in a wall of the collection container 6. Alternatively or additionally, an electroacoustic and/or electromechanical actuator can be arranged on or in the container lid 7 and/or on or in the annular sieve 5.

(22) In addition, it is possible to arrange a sound-generation unit 17 in the region of the wall portion 10 of the housing lid 11 defining the milling stock tube 8 and/or on the housing 12. A sound-generation unit 17 can also be arranged on a side wall 26 of the housing lid 11 spaced apart from the milling stock tube 8. For device and/or housing parts arranged so as to be capable of vibrating, an electromechanical actuator can also interact with a device and/or housing wall and cause said wall to vibrate in order to thus generate counter-sound. The housing wall can then act as a membrane and generate the counter-sound.

(23) It goes without saying that there are further options for arranging a counter-sound apparatus 14 other than the positions X shown in FIG. 1 for a counter-sound apparatus 14.

(24) FIG. 3 schematically shows a counter-vibration apparatus 27 for a laboratory mill 1 shown in FIG. 1. The counter-vibration apparatus 27 preferably has a plurality of sensors 28 and an actuable vibration-generation unit 29. Just one sensor 28 can also be provided. Also provided is a control unit 29a, which generates a counter-vibration signal 29b. The vibration-generation unit 29 is designed to convert the counter-vibration signal 29b into counter-vibrations 30 to actively reduce the vibrations of a device and/or housing part 31, otherwise capable of vibrating, of the comminution machine 1. This ensures that vibrations 32 of the device and/or housing part 31 generated when the laboratory mill 1 is in operation are reduced or even completely eliminated due to the action of the vibration-generation unit 29. As a result, less disruptive sound is emitted.

(25) The vibration-generation unit 29 can be a piezoelectric actuator and/or an electromechanical actuator in the form of a spring-mass vibration system. The vibration-generation unit 29 is preferably placed on the device and/or housing part 31 and/or acts counter to the device and/or housing part 31. In principle, the vibration-generation unit 29 can also be integrated or embedded in a wall of the device and/or housing part 31.

(26) A modular system may also be provided, which comprises at least one vibration-generation unit 29 and at least one sensor 28, preferably a plurality of sensors, and can be used as required for vibration reduction. In order to reduce vibrations in as optimum a manner as possible, it is thus possible to attach at least one vibration-generation unit 29, which can be connected to the device and/or housing part 31, to different points on a device and/or housing part 31 or even to different device and/or housing part parts 31 depending on the vibrations 32 actually occurring during operation of the mill.

(27) The sensors 28 can be formed as accelerometers and are preferably arranged so as to be distributed spatially over the device and/or housing part 31, which in this case is shown as being plate-shaped merely for the purpose of simplifying the illustration. Said sensors are placed on the surface of the device and/or housing part 31 such that the vibrations 32 of the device and/or housing part 31 generated during the milling process are detected. The sensor output signals 28a are then fed to the control unit 29a, which generates counter-vibration signals 29b and transmits these to the vibration-generation unit 29 for active vibration reduction. A microphone can also be provided as a sensor 28 in order to detect disruptive sound emanating from the device and/or housing part 31 during operation in the laboratory and to convert said sound into a sensor output signal 28.

(28) From the counter-vibration signals 29b, the vibration-generation unit 29 then generates counter-vibrations 30, which excite the device and/or housing part 31 in phase opposition and counteract the vibrations 32 of the device and/or housing part 31. Vibrations of the device and/or housing part 31 are attenuated. As a result, disruptive sound or noise radiated from the device and/or housing part 31 is significantly reduced or completely eliminated. The signals can be transmitted between the sensors 28, the vibration-generation unit 29 and the control unit 29a via radio or by means of control signal lines. The control unit 29a can be formed as a closed-loop controller.

(29) FIG. 4 schematically shows possible positions for arranging a counter-vibration apparatus 27 on a comminution machine 1. The counter-vibration apparatus 27 is used to actively excite device and/or housing walls of the comminution machine 1 in phase opposition, in order to reduce vibrations of the device and/or housing walls caused by the milling operation. This also reduces disruptive sound.

(30) The type and design of the laboratory mill 1 shown in FIG. 4 corresponds to the laboratory mill 1 shown in FIG. 1, although a separate feed funnel 33 is inserted into the milling stock tube 8. The feed funnel 33 is formed as a sound absorber and leads to passive reduction of sound emissions by reflecting airborne sound at cross-sectional and/or directional changes in the feed funnel 33.

(31) For example, a counter-vibration apparatus 27 can be provided on or in the region of an outer or inner wall of the housing 12. A counter-vibration apparatus 27 formed accordingly can also be provided in the region of the housing lid 11, in particular in the region of the wall portion 10 defining the milling stock tube 8. The counter-vibration apparatus 27 can be arranged externally or internally on the relevant wall of the housing 12 and/or housing lid 11. It can also be integrated in the wall. FIG. 4 further shows that a counter-vibration apparatus 27 can also be provided directly on the feed funnel 33, preferably on the outer side of the feed funnel 33 facing away from the milling stock.

(32) In the laboratory mill 1 shown in FIG. 4, the base plate 13 rests on a base by means of rubber elements 34. The rubber elements 34 lead to the base plate 13 being passively decoupled from the base and to the transmission of vibrations being passively attenuated. In conjunction therewith, at least one counter-vibration apparatus 27 can be provided in order to excite the base plate 13 in phase opposition and thus to provide additional active decoupling. By exciting the base plate 13 in phase opposition, vibrations of the base plate 13 that generate disruptive sound can be actively reduced and/or at least partly eliminated. Each rubber element 34 can be assigned a counter-vibration apparatus 27.

(33) FIGS. 5 and 6 show alternative embodiments of feed funnels 33 that can be inserted as required into the milling stock tube 8 of a laboratory mill 1 as separate device parts and lead to passive reduction of sound emissions by reflecting airborne sound at cross-sectional and/or directional changes in the funnel 33. For this purpose, the funnel 33 is introduced into the airborne-sound path between the milling chamber 4 and the external air surrounding the comminution machine 1. In the funnel 33, obstacles are placed in the path of the sound waves such that they are reflected and deflected. In the process, the sound waves also cancel each other out in part. By the absorber having different cross sections, the sound is reflected and thus sound levels are reduced. The reduction of sound emissions caused by the geometry of the funnel 33 can be at least 10 dB(A), preferably at least 20 dB(A), particularly preferably at least 30 dB(A).

(34) The feed funnel 33 shown in FIG. 5 has an upper edge portion 35 provided for supporting the feed funnel 33 on the housing lid 11. At its upper end, the feed funnel 33 has a conically tapering funnel portion 36 and a cylindrical neck portion 37 connected to the bottom thereof. At the lower end of the neck portion 37, an anti-splashback guard 38 is provided, which is formed by a conical wall portion 39. The wall portion 39 is held on the neck portion 37 by means of wall portions 40 that are extended in the axial direction in the manner of webs. Milling stock is fed into the milling chamber 4 through an entry opening 41 at the upper end of the feed funnel 33, through the funnel portion 36 and neck portion 37, past the web-shaped wall portions 40 towards the milling chamber 4.

(35) As is now also clear from FIG. 5, at least one counter-vibration apparatus 27, in particular of the type shown in FIG. 3, can be provided externally at different points of the feed funnel 33. In this way, the feed funnel 33 can be actively excited in phase opposition during operation of the laboratory mill 1, leading to vibration reduction and at least partial elimination of vibrations of the feed funnel 33 that generate disruptive sound. The fact that a counter-sound apparatus 14 can alternatively or additionally be provided on the funnel 33 is not shown.

(36) FIG. 6 shows an alternative embodiment of a feed funnel 33 formed in multiple parts. The same reference numerals for the funnels 33 shown in FIGS. 5 and 6 denote the same regions and portions and/or those having the same function. The feed funnel 33 from FIG. 6 comprises an insert 43 having a funnel-shaped wall portion 44, which forms the anti-splashback guard 38 at its lower end. The insert 43 can be held in the entry opening 41 of the feed funnel 33 in a locked manner.

(37) The counter-vibration apparatus 27 can, for example, be provided on an outer edge 42 of the edge portion 35. In addition, a counter-vibration apparatus 27 can be provided on the funnel portion 36 and/or on the neck portion 37 and/or in the region of the anti-splashback guard 38.

(38) In the embodiment shown in FIG. 6, a counter-vibration apparatus 27 can also be provided on the insert 43, counter-vibrations 30 being transmitted to the insert 43 in order to attenuate the vibrations of the insert 43 and reduce or even completely eliminate vibrations and thus disruptive sound emanating from the insert 43 during operation of the laboratory mill 1.

(39) FIG. 7 shows the feed funnel 33 from FIG. 6 after being inserted into the milling stock tube 8 of a laboratory mill 1. As is clear from FIG. 7, milling stock can be fed into the feed funnel 33 in an off-center manner. The milling stock can be fed via a channel 45 guided through a cover 46. The cover 46 covers the feed funnel 33 inserted into the milling stock tube 8 and can lie on the outer edge 42 of the feed funnel 33. A counter-vibration apparatus 27 can also be provided on the cover 46 and/or on the channel 45. The fact that a counter-sound device 14 can also be provided on the cover 46 and/or on the channel 45 is not shown.

(40) The type and design of the laboratory mill 1 shown in FIG. 8 corresponds to those of the laboratory mill 1 shown in FIGS. 1, 4 and 7. Identical components and/or those having the same function have been denoted by the same reference numerals.

(41) The laboratory mill 1 from FIG. 8 comprises a feed funnel 33 that allows milling stock to be fed in an off-center manner. The feed funnel 33 is preferably rotatably inserted into a funnel housing 47. The funnel housing 47 is preferably supported on the housing lid 11 and thus covers the milling stock tube 8. The illustrated geometry of the arrangement consisting of the feed funnel 33 and funnel housing 47 leads to passive sound emission reduction during operation of the comminution machine 1. To reduce the generation of sound emissions, at least one counter-vibration apparatus 27 can be arranged, for example, on the housing lid 11, on the funnel housing 47 or also directly on the feed funnel 33.

(42) The features of the laboratory mills 1 shown in FIG. 1 to 8 are not limited to the collection of features shown in each figure, and features from different embodiments can be combined as required, even if this has not been shown and described specifically.

(43) TABLE-US-00001 List of reference numerals 1 laboratory mill 2 drive shaft 3 rotor 4 milling chamber 5 annular sieve 6 collection container 7 container lid 8 milling stock tube 9 milling stock inlet opening 10 wall portion 11 housing lid 12 housing 13 base plate 14 counter-sound apparatus 15 control unit 16 counter-sound signal 17 sound-generation unit 18 counter-sound field 19 disruptive-sound field 20 counter-sound wave 21 disruptive-sound wave 22 microphone 23 interference signal 24 microphone 25 error signal 26 side wall 27 counter-vibration apparatus 28 sensor 28a vibration signal 29 vibration-generation unit 29a control unit 29b counter-vibration signal 30 counter-vibration 31 device and/or housing part 32 vibration 33 feed funnel 34 rubber element 35 edge portion 36 funnel portion 37 neck portion 38 anti-splashback guard 39 wall portion 40 wall portion 41 entry opening 42 outer edge 43 insert 44 wall portion 45 channel 46 cover 47 funnel housing