Patent Description:
Mineral material, for example rock, is gained from the earth for crushing by exploding or excavating. The rock can also be natural rock and gravel or construction waste. Mobile crushers and stationary crushing applications are used in crushing. An excavator or wheel loader normally loads the material to be crushed into the crusher's feed hopper from where the material to be crushed may fall in a jaw of a crusher or a feeder, like a conveyer, moves the rock material towards the crusher. The material to be crushed may also be recyclable material such as concrete, bricks, or asphalt.

Another common way of conveying a material in the plant is through a chute which is advantageous compared with letting it fall freely since the large amounts of dust that would otherwise occur will be reduced. Moreover, a free fall will not contain the material in a stream. In a telescopic chute, the falling material generates a pressure below atmospheric in the chute, whereby air is drawn into the space between the chute elements and dust is prevented from being spread.

The material which is crushed in a crusher is finally transported from the crusher to a screen. The product passing through the screen, or going over the screen deck, can be guided to further processing in the same plant or another plant which processes mineral material, or to a pile.

There are a number of problems that may occur when handling the material in the plant, such as material build-up, over-loaded screens, worn screen elements and over-sized material getting stuck during transport.

<CIT> relates to a vibratory separator having a sensor apparatus for sensing a parameter indicative of basket angle and for providing a signal corresponding to said basket angle.

<CIT> relates to a screen device, and more particularly, to a screen device that can improve the efficiency of the particle size screening process and which screen device includes a sensor unit configured to measure a transfer amount of the material screened.

<CIT> relates to an ultrasonic wave transmitter/receiver for measuring a distance between spray painting equipment and an object to be painted by transmitting and receiving ultrasonic waves.

<CIT> relates to an ultrasonic measurement system for measuring a range to a hot target such as a hot ingot.

It is an objective of the present invention to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solve at least the above mentioned problems.

According to a first aspect, these and other objects, and/or advantages that will be apparent from the following description of embodiments, are achieved, in full or at least in part, by an arrangement for handling screening material according to claim <NUM>. The arrangement comprises an ultrasonic detection system. The arrangement further comprises a screening deck on or in relation to which screening material is traveling.

The ultrasonic detection system comprises an ultrasonic transmitter arranged at the arrangement, and adapted to send out an ultrasonic signal towards the surface, an ultrasonic receiver adapted to receive the ultrasonic signal, and a control unit connected to the ultrasonic transmitter and the ultrasonic receiver. The control unit is adapted to detect at least one parameter of the ultrasonic signal.

The term screening material should be interpreted as material intended to be screened, transported or processed. The material could be aggregate, ore or similar.

The at least one parameter may thereafter be used to draw conclusions relating to the operational status of the arrangement.

This is advantageous in that any potential operation problems of the arrangement can be detected in a simple and reliable way. The solution is also cost efficient compared to the solutions available on the market today.

The control unit is adapted to detect a difference in the at least one parameter based on a comparison between the ultrasonic signal and a reference signal.

When a time period is used as the comparison parameter, the control unit will detect the time period it takes for the ultrasonic signal to travel to the surface of the arrangement or the screening material present on the surface, and back to the ultrasonic receiver. That time period may thereafter be compared with the corresponding time period of a reference signal.

Specifically, the detected time period can for example be compared with a targeted time period stored in the control unit or read from a table. It can also be compared with a detected time period of a reference signal which is conducted in the same manner as described above when the arrangement is running without load. , i.e. under ideal circumstances. In case the arrangement comprises a screen, the control unit may be configured to learn a stroke of a vibrating screen deck of the screen and set that as a reference value. Should the difference between the time period of the ultrasonic signal and the reference signal deviate more than a predetermined error margin it can be concluded that there is an operating deviation with arrangement, potentially indicating a problem.

The ultrasonic detection system further comprises: a reflector arranged for deflecting the ultrasonic signal towards the surface of the screening deck of the arrangement, and; a mesh which comprises a plurality of ultrasonic transmitters and ultrasonic receivers wherein each ultrasonic transmitter and ultrasonic receiver is arranged over the surface of the screening deck of the arrangement.

The ultrasonic transmitter may be arranged close to an edge of the arrangement. The ultrasonic transmitter may further be arranged on any other part of the arrangement, such as anywhere on a screen deck, or beside, behind or below a screen deck or between adjacent screen decks. The arrangement may comprise a screen. The ultrasonic transmitter may be arranged at a screen deck of the screen being close to a discharge end of the screen deck. It may be advantageous to detect the ultrasonic signal just before the material fall off the screen deck.

The ultrasonic detection system may further comprise cleaning means connected to the control unit and arranged at the one ultrasonic transmitter and the ultrasonic receiver, wherein the control unit is adapted to control a cleaning process of the ultrasonic transmitter and/or the ultrasonic receiver using the cleaning means.

According to alternative embodiments, the ultrasonic detection system further comprises a cleaning means connected to a further control unit and arranged at the ultrasonic transmitter and the ultrasonic receiver, wherein the further control unit is adapted to control a cleaning process of the ultrasonic transmitter and/or the ultrasonic receiver using the cleaning means. The use of separate control units for controlling the ultrasonic transmitter/receiver and the cleaning means may be advantageous as it allows for an easier and more flexible system increasing the ease of customization.

The control unit may be adapted to report that a problem has been identified if the difference in the at least one parameter is outside of an acceptable interval. This implies that the control unit may be adapted to report that a problem has been identified if the difference in the at least one parameter is above a threshold value. It may further imply that that the control unit may be adapted to report that a problem has been identified if the difference in the at least one parameter is below a threshold value.

The ultrasonic detection system may further comprise a protective case at least partly housing the ultrasonic transmitter and the ultrasonic receiver.

The protective case may be inclined in relation to the surface of the arrangement, and the cleaning means may comprise air blowing means.

One or more from the ultrasonic transmitter and the ultrasonic receiver may comprise a piezo element.

The ultrasonic transmitter and the ultrasonic receiver may be constituted by one single element, the single element comprising a piezo element.

The ultrasonic transmitter and the ultrasonic receiver may be arranged at the arrangement to face each other in an opposing manner.

The at least one parameter is constituted by a time period, a frequency of the ultrasonic signal, and/or an amplitude of the ultrasonic signal.

The parameter to be analysed by the control unit can be the time period it takes for the ultrasonic signal to travel from the ultrasonic transmitter to the surface of the arrangement of the material present on the surface, and back to the ultrasonic receiver. It can also be the actual frequency or the amplitude of the ultrasonic signal as well as a combination of all of the above.

The reference signal can be constituted by a predetermined signal which for example is read from a table based on the screening material present on the screen when the ultrasonic signal is sent. It can also be constituted by an actual measurement conducted in the same manner as described above but at an earlier or later stage.

The arrangement may comprise a plant, a screen, a screening deck, a conveyor belt, a chute, a feed box or a discharge box.

According to a second aspect, these and other objects are achieved, in full or at least in part, by a method for monitoring operation of an arrangement for handling screening material, e.g. aggregate, ore or similar. The method comprises the steps of sending out an ultrasonic signal from an ultrasonic transmitter towards a surface of the arrangement, receiving the ultrasonic signal by an ultrasonic receiver, and detecting at least one parameter of the ultrasonic signal.

The method may further comprise the step of comparing the ultrasonic signal with a reference signal based on the at least one parameter, and conducting a specific action if a difference in the at least one parameter between the ultrasonic signal and the reference signal outside of an acceptable interval.

Effects and features of the second aspect of the present invention are largely analogous to those described above in connection with the first aspect of the inventive concept. Embodiments mentioned in relation to the first aspect of the present invention are largely compatible with the further aspects of the invention.

According to another example not forming part of the appended claims, a cleaning detection system in an arrangement for handling screening material, e.g. aggregate, ore or similar, is provided. The cleaning system comprises at least one ultrasonic transmitter arranged at a surface of the arrangement, and adapted to send out an ultrasonic signal towards the surface, at least one ultrasonic receiver arranged at the surface, and adapted to receive the ultrasonic signal, and a protective case at least partly housing the at least one ultrasonic transmitter and the at least one ultrasonic receiver. The cleaning detection system is characterised in that it further comprises a control unit connected to the at least one ultrasonic transmitter and the at least one ultrasonic receiver, and adapted to detect a difference in at least one parameter based on a comparison between the ultrasonic signal and a reference signal.

The cleaning detection system may further comprise cleaning means arranged at the protective case, the cleaning means may in turn comprise air blowing means adapted to clean the protective case.

The control unit may be configured to control the cleaning means. For example, the control unit may be configured to activate air blowing means in timely intervals. Alternatively, the control unit may be configured to activate and control air blowing means for continuous operation.

The control unit may comprise more than one control sub unit. For example, a first control sub unit may be configured to control the cleaning means and a second control sub unit may be configured to control the ultrasonic transmitter and the ultrasonic receiver. The control sub units may be connected to each other, but alternatively, the control sub units may be operating independent from each other. The cleaning detection system may be actively checked for dirt and, in case dirt is detected, the cleaning means may be activated to clean the system.

The at least one ultrasonic transmitter and the at least one ultrasonic receiver may be constituted by one single element, wherein the single element comprises a piezo element.

The at least one ultrasonic transmitter and the at least one ultrasonic receiver may be comprised in one single unit.

The at least one ultrasonic transmitter and the at least one ultrasonic receiver may be arranged at the arrangement to face each other in an opposing manner.

The signal may be sent out in a direction substantially perpendicular to the surface of the arrangement.

The signal may be sent out in a direction forming an oblique angle to the surface of the arrangement.

The angle may be adjustable to allow optimizing the system.

The at least one parameter may be constituted by a time period, a frequency of the ultrasonic signal, and/or an amplitude of the ultrasonic signal.

The control unit may be adapted to report that problem has been identified if the difference in the at least one parameter is outside of an acceptable interval.

The control unit may further be connected to the cleaning means, and adapted to initiate cleaning of the protective case by means of the cleaning means at predetermined time intervals.

According to yet another example not forming part of the appended claims, a method for detecting a cleaning requirement of an arrangement for handling screening material, e.g. aggregate, ore or similar, is provided. The method comprises the steps of sending out an ultrasonic signal towards a surface of the arrangement, and receiving the ultrasonic signal. The method is characterised by the step of detecting a difference in at least one parameter based on a comparison between the ultrasonic signal and a reference signal.

The method may further comprise the step of conducting a specific action if the difference in the at least one parameter is outside of an acceptable interval.

According to yet another example not forming part of the appended claims, a detection system in an arrangement for handling screening material, e.g. aggregate, ore or similar, is provided. The detection system comprises two or more ultrasonic transmitters, arranged at different positions of the arrangement and, each, adapted to send out an ultrasonic signal towards a surface of the arrangement, and two or more ultrasonic receivers, each adapted to receive the respective ultrasonic signal. The detection system is characterised in that it further comprises a control unit connected to the ultrasonic transmitters and the two or more ultrasonic receivers, and adapted to detect a difference in at least one parameter based on a comparison between the ultrasonic signals and a reference signal.

By comparing the parameters of the ultrasonic signals, information regarding for example the material distribution over the surface of the screen can be evaluated.

According to an embodiment, an ultrasonic transmitter and an ultrasonic receiver are comprised in one single unit, referred to as an ultrasonic detection unit. A detection system in an arrangement comprising two or more ultrasonic detection units is thus provided.

According to an embodiment, the detection system comprises two ultrasonic units. The two ultrasonic units can be arranged at different positions of the arrangement, such as along the extension of a screening deck. As an example, a first ultrasonic unit can be arranged at a first side of the screening deck whereas a second ultrasonic unit can be arranged in parallel with the first ultrasonic unit at a second side of the screening deck. By means of the control unit connected to a monitoring system, the material flow of each of the first and second sides of the screening deck can be monitored and evaluated, giving an indication of the material distribution.

According to an embodiment, the detection system comprises a mesh comprising at least six ultrasonic transmitters and six ultrasonic receivers distributed over the surface of a screening deck of the arrangement deck. By arranging a mesh comprising plurality of ultrasonic transmitters and ultrasonic receivers, or ultrasonic detection units over the surface of the screening deck, the material flow thereon can be evaluated and monitored over a larger area. This provides the possibility of detecting an abnormality, such as a tilting screen or uneven material distribution, at an early stage and thus allowing for an early remedy of such an abnormality. Thereby, the operation efficiency of the screening arrangement is increased.

According to an embodiment, the detection system comprises a moveable structure on which one or more ultrasonic units is arranged. The moveable structure can be used to move the ultrasonic unit in accordance with a pattern, preferably according to a predetermined pattern, such that the whole surface, or at least preferred parts thereof, of the screening deck can be covered.

The at least one parameter may be constituted by a time period, a
frequency of the ultrasonic signal, and/or an amplitude of the ultrasonic signal.

The control unit may be adapted to report that a problem has been identified if the difference in the at least one parameter is outside of an acceptable interval.

According to yet another example not forming part of the appended claims, a bed depth detection system in an arrangement for handling screening material, e.g. aggregate, ore or similar, is provided. The bed depth detection system comprises at least one ultrasonic transmitter arranged at a portion the arrangement on or in relation to which the screening material is traveling, and adapted to send out an ultrasonic signal towards the surface, and at least one ultrasonic receiver adapted to receive the ultrasonic signal. The bed depth detection system is characterised in that it further comprises a control unit connected to the at least one ultrasonic transmitter and the at least one ultrasonic receiver, and adapted to calculate a bed depth of the screening material present on the surface from a comparison between the ultrasonic signal and a reference signal based on at least one parameter.

The bed depth detection system may be arranged at a portion of the arrangement being close to an edge of the arrangement. The arrangement may comprise a screen. The bed depth detection system may be arranged at any portion of a screen deck, such as for example close to a discharge end of the screen deck. It may be advantageous to detect the bed depth on the material on the screen deck just before the material fall off the screen deck.

The at least one ultrasonic transmitter and the at least one ultrasonic receiver may be constituted by one single element, the single element comprising a piezo element.

The at least one ultrasonic transmitter and the at least one ultrasonic receiver may be arranged at the surface of the arrangement to face each other in an opposing manner.

The bed detection system may comprise two or more ultrasonic transmitters and two or more ultrasonic receivers positioned to detect the bed depth at different portions of a surface of a screen deck. This may allow material distribution over the surface of the screen to be monitored and evaluated. An ideal distribution of the material may be the same bed thickness over an entire width of the screen deck whereas the bed depth will decrease from an upstream position towards a downstream position.

The signal may be sent out in a direction substantially perpendicular to the surface of the arrangement on or in relation to which the screening material is traveling.

The control unit may be adapted to report that problem has been identified if the calculated bed depth is outside of an acceptable interval.

The control unit may be adapted to operate the arrangement based on information from the ultrasonic signal.

The arrangement may comprise a screen, a screening deck, a conveyor belt, a chute, a feed box or a discharge box.

According to yet another example not forming part of the appended claims, a method for detecting a bed depth of a screening material, e.g. aggregate, ore or similar, is provided. The method comprising the steps of sending out an ultrasonic signal towards a surface on or in relation to which the screening material is traveling, and receiving the ultrasonic signal. The method is characterised by the step of calculating the bed depth of the screening material present on the surface from a comparison between the ultrasonic signal and a reference signal based on at least one parameter.

According to an embodiment, the method may further comprise the step of monitoring the bed depth calculated from two or more ultrasonic signals and identifying a problem in the arrangement based on the monitored bed depths. As an example, the bed depth is calculated from two ultrasonic signals received by ultrasonic receivers arranged at different positions of a screening deck and monitored in parallel allowing a comparison of the bed depth of the two positions of the screening deck. This allows for monitoring and evaluating the material distribution on the screening deck.

A problem detected may be a tilting screen of a screen deck of the arrangement. By detecting this problem, it can be deduced that a support structure of the screen is damaged, for example that a spring is missing, causing the screen to tilt. A tilting screen can cause unusual wear on the screening deck and it is therefore an advantage to detect this problem at an early stage such that it can be repaired.

A problem detected may be an overload of a screen deck of the arrangement. Such a problem is detectable when one bed depth calculated from one ultrasonic signal, received from a first position of the surface of the screening deck, is continuously larger than a bed depth calculated from an ultrasonic signal received from a second position of the surface, and near a pre-set critical limit for the bed depth.

A problem detected may be a lost screening module. Such event would be detectable in that the bed depth on the position of that screening module would become negative and the bed depth at the screening module downstream of the lost module all of a sudden would become zero and also in that the bed depth on a corresponding position on a subjacent screen deck suddenly would increase.

A problem detected may be an uneven material distribution on a screening deck of the arrangement. Such a problem is detectable when one bed depth calculated from one ultrasonic signal, received from a first position of the surface of the screening deck, is continuously larger than a bed depth calculated from an ultrasonic signal received from a second position of the surface. This will cause more wear on the part of the screening deck where the bed depth is larger, reducing thereby the efficiency of the screen. It is thus desirable to detect such a problem as early as possible in the process in order to remedy the same for a fully efficient screening arrangement.

The method may further comprise the step of conducting a specific action if the calculated bed depth is outside of an acceptable interval.

The reflector allows deflecting the ultrasonic signal sent out by the ultrasonic transmitter towards a surface which is at an angle from the transmitter. Correspondingly, the reflector further deflects the ultrasonic signal reflected back from the surface to the ultrasonic receiver. Thereby, positions of the arrangement in which the ultrasonic transmitter and the ultrasonic receiver are not mountable due to limited access or other, can still be subjected to the signal such that the at least one parameter of the ultrasonic signal can be detected therefrom.

According to an embodiment of the arrangement, the reflector is arranged in a blind zone of the ultrasonic transmitter.

According to an embodiment of the arrangement, the reflector is arranged at a distance from the ultrasonic transmitter and the ultrasonic receiver and at a portion of the arrangement different from the structure at which the ultrasonic transmitter and the ultrasonic receiver are arranged. As an example, the reflector can be arranged at a portion inside the arrangement and the ultrasonic transmitter and the ultrasonic receiver can be arranged at or in line with an opening of a wall of the arrangement. Thereby, the ultrasonic transmitter and the ultrasonic receiver can be arranged at a distance from the material processing environment, avoiding subjecting these parts to any dirt and vibrations therefrom.

According to an embodiment of the arrangement, the reflector is arranged at the same structure of the arrangement as the ultrasonic transmitter and the ultrasonic receiver.

According to an embodiment of the arrangement, the reflector is arranged at a non-vibrating surface of the arrangement. This provides a stable reflection of the ultrasonic signal.

According to an embodiment of the arrangement, the reflector is arranged at a vibrating surface of the arrangement. This might be necessary to direct the ultrasonic signal towards a surface of particular interest. The ultrasonic receiver is, in this embodiment, adapted to detect an average value of the signal reflected by the vibrating reflector.

According to an embodiment of the arrangement, the reflector is arranged at an angle of <NUM>° with respect to the plane in which the ultrasonic transmitter is arranged. This allows for a deflection of the ultrasonic signal of <NUM>°, and thereby parameters of a surface arranged vertically from the plane of the ultrasonic transmitter can be obtained. The ultrasonic transmitter can therefore be arranged at a structure at which it is not subjected to the working environment.

According to an embodiment of the arrangement, the reflector, the ultrasonic transmitter and the ultrasonic receiver are comprised in one single unit. The single unit may comprise a protective case which at least partly houses the ultrasonic transmitter, the ultrasonic receiver and the reflector. An advantage of such a single unit is that it can be arranged at a structure in the working environment of the arrangement at an angle from a surface to be subject to analysis. At least partly housed by the protective case, the ultrasonic transmitter and the ultrasonic receiver are protected from dust and dirt of the working environment. The single unit may also comprise a cleaning means as previously disclosed herein.

Other objectives, features and advantages of the present invention will appear from the following detailed disclosure, from the attached claims, as well as from the drawings. It is noted that the invention relates to all possible combinations of features.

All references to "a/an/the [element, device, component, means, step, etc.]" are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise.

As used herein, the term "comprising" and variations of that term are not intended to exclude other additives, components, integers or steps.

As used herein, the term "ultrasonic signal" and variations of that term should be interpreted as the total ultrasonic sound wave pattern resulting from initiating a transmission from the ultrasonic transmitter. Hence, the ultrasonic signal comprises the emitted "clean" wave pattern propagating away from the ultrasonic transmitter as well as any reflected wave patterns originating from said transmitted wave pattern.

The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of embodiments of the present invention, with reference to the appended drawings, where the same reference numerals may be used for similar elements, and wherein:.

<FIG> illustrates an arrangement <NUM> for handling screening material <NUM>, e.g. aggregate, ore or similar, according to an example embodiment.

The arrangement <NUM> comprises a screen <NUM> comprising at least one screen deck 112a, 112b, 112c (in the example: three screen decks). The at least one screen deck 112a, 112b, 112c is attached to vibrating means (not shown) arranged to cause a vibration of the at least one screen deck 112a, 112b, 112c. The vibration causes the at least one screen deck 112a, 112b, 112c to be located at different positions at different times. Specifically, the vibration causes the at least one screen deck 112a, 112b, 112c to be located at different vertical positions for different times. This is illustrated for an uppermost screen 112a of the at least one screen deck 112a, 112b, 112c in <FIG>. The vibration means is not explicitly disclosed herein. It should be understood that many alternative ways exist for achieving said vibrations within the scope of the claims.

The screen <NUM> further comprises input means <NUM> arranged to input screening material onto the at least one screen 112a, 112b, 112c. For the screen <NUM>, the screening material <NUM> is input, via the input means <NUM>, onto an uppermost screen deck 112a. The uppermost screen deck 112a has a plurality of through holes covering a portion of its surface. As the uppermost screen deck 112a vibrates, screening material <NUM> located thereon will be caused to move around. Pieces of the screening material <NUM> with dimensions smaller than the dimensions of the through holes are allowed to leave the uppermost screen deck 112a via the plurality of through holes, ending up at a middlemost screen deck 112b located under the uppermost screen deck 112a. Screening material with dimensions larger than the dimensions of the through holes of the uppermost screen deck 112a is allowed to leave the uppermost screen deck 112a at an end thereof, as illustrated in <FIG>. The middlemost screen deck 112b has a plurality of through holes wherein the through holes have dimensions smaller than the dimensions of the through holes of the uppermost screen deck 112a. Thus, as the middlemost screen deck 112b vibrates, screening material <NUM> located thereon will be caused to move around. Pieces of the screening material <NUM> with dimensions smaller than the dimensions of the through holes of the middlemost screen deck 112b are allowed to leave the middlemost screen deck 112b via the plurality of through holes, ending up at a lowermost screen deck 112c located under the middlemost screen deck 112b. As for the uppermost screen deck 112a, screening material <NUM> on the middlemost screen deck 112b with dimensions larger than the dimensions of the through holes of the middlemost screen deck 112b is allowed to leave the middlemost screen deck 112b at an end thereof. The same process is repeated for the lowermost screen deck 112c.

Thus, it is understood that the purpose of the screen <NUM> is to sort, or separate, the screening material <NUM> according to their size. To the end, this is achieved by collecting the screening material <NUM> leaving each screen deck at an edge thereof, and, for the smallest dimensions, under the lowermost screen deck 112c.

The arrangement <NUM> further comprises an ultrasonic detection system <NUM>.

The ultrasonic detection system <NUM> comprises an ultrasonic transmitter 151a arranged at a surface 142a of the arrangement <NUM>. The ultrasonic transmitter 151a is adapted to send out an ultrasonic signal 154a towards the surface 142a.

The ultrasonic detection system <NUM> further comprises an ultrasonic receiver 152a arranged at the surface 142a, and adapted to receive the ultrasonic signal 154a.

The ultrasonic transmitter 151a and the ultrasonic receiver 152a may be constituted by one single element. Such a single element may be a transceiver. Specifically, for the ultrasonic detection system <NUM>, the ultrasonic transmitter 151a and the ultrasonic receiver 152a are constituted by one single element, the single element comprising a piezo element. Alternatively, the ultrasonic transmitter 151a and the ultrasonic receiver 152a may be constituted by one single element the single element comprising a capacitive transducer.

The sound waves transmitted by the ultrasonic transmitter 151a (i.e. the ultrasonic signal 154a) may be in the ultrasonic range, with an operating frequency, f, above <NUM>. One typical operating frequency range is <NUM> < f < <NUM>. However, it is understood that the choice of operating frequency affects the effective distance that may be used for detection as a result from the attenuation losses of the sound waves increasing with operating frequency. Hence, the operating frequency may depend on the application.

The ultrasonic detection system <NUM> may be used for monitoring operation of the arrangement that handles the screening material <NUM>. A method for monitoring operation of an arrangement such as the arrangement <NUM> comprises the steps of sending out an ultrasonic signal 154a from ultrasonic transmitter 151a towards a surface 142a of the arrangement <NUM>, receiving the ultrasonic signal 154a by ultrasonic receiver 152a, and detecting at least one parameter of the ultrasonic signal 154a.

The method may further comprise the step of comparing the ultrasonic signal 154a with a reference signal based on the at least one parameter.

The method may further comprise the step of conducting a specific action if a difference in the at least one parameter between the ultrasonic signal 154a and the reference signal is outside of an acceptable interval. The ultrasonic detection system <NUM> further comprises a control unit <NUM> connected to the ultrasonic transmitter 151a and the ultrasonic receiver 152a. The control unit <NUM> is adapted to detect at least one parameter of the ultrasonic signal 154a.

The at least one parameter may be constituted by a time period. In such a case, the ultrasonic detection system <NUM> may be arranged to detect a distance to a target by determining a time delay between a time of transmitting and a time of receiving an ultrasonic signal 154a transmitted in a direction of the target. The distance to the target may then be calculated with knowledge of the speed of sound. The target may be the surface 142a, the material present on the surface 142a or a combination of the surface 142a and the material present onto the surface 142a.

Alternatively, the at least one parameter may be constituted by a frequency of the ultrasonic signal 154a. In such a case, the ultrasonic detection system <NUM> may be arranged to detect a speed of a target with respect to the ultrasonic detection system <NUM>. The speed of the target may be calculated with knowledge of the speed of sound by utilizing the formulation of the Doppler effect for sound waves.

Alternatively, the at least one parameter may be constituted by an amplitude of the ultrasonic signal 154a. In such a case, the ultrasonic detection system <NUM> may be arranged to detect surface properties of a target.

Although discussed separately, any combination of the properties of time, frequency and amplitude may be used to achieve a purpose of the ultrasonic detection system <NUM>. Other properties may also be used. For example, the spatial distribution of the ultrasonic signal 154a may be used to infer properties of the target. For such a case, the ultrasonic receiver 152a may comprise a spatially resolving sensor. Furthermore, the properties of the ultrasonic signal 154a transmitted by the ultrasonic transmitter 152a may be different depending on the purpose. For example, the ultrasonic signal 154a may be pulsed or continuous. Furthermore, the base frequency of the ultrasonic signal 154a may vary dependent on the purpose.

The control unit <NUM> may be adapted to detect a difference in the at least one parameter based on a comparison between the ultrasonic signal 154a and a reference signal. The reference signal may be for example the signal detected by the control unit <NUM> in a case where no screening material is affecting the ultrasonic signal 154a. For example, a reference signal may be recorded and stored when the screen <NUM> is empty. Alternatively, or additionally, a reference signal may be the signal detected by the control unit <NUM> for a specific position of the vibrating screen. For example, the reference signal may be the signal detected by the control unit <NUM> when a screen deck is in its default position.

There are numerous advantages and usefulness of the ultrasonic detector of the disclosure. This will be further discussed later in the detailed description. For example, the control unit <NUM> may be adapted to report that problem has been identified if the difference in the at least one parameter is outside of an acceptable interval. The report may comprise for the control unit <NUM> to issue an alarm and/or notification. Alternatively, or additionally, the control unit <NUM> may initiate a command initiating an action solving, or at least mitigating, the problem. The command may be issued to a further unit, or internally within the control unit <NUM>. The command may pertain to initiating a calculation such as to derive for example a physical parameter. Alternatively, or additionally, the command may pertain to the control unit <NUM> (or further unit) to initiate a control action with regards to the arrangement <NUM>. Specifically, for the arrangement <NUM>, the control unit <NUM> may initiate a command pertaining to controlling the operation of the vibrating means. This may include for example adjusting the vibrating frequency or stopping the vibrations. Alternatively, the control unit <NUM> may initiate a command pertaining to controlling the operation of the input means <NUM> for controlling the feed rate therefrom.

The ultrasonic detection system <NUM> further comprises cleaning means <NUM> connected to the control unit <NUM> and arranged at the ultrasonic transmitter 151a and the ultrasonic receiver 152a. The control unit <NUM> is adapted to control a cleaning process of the ultrasonic transmitter 151a and/or the ultrasonic receiver 152a by means of the cleaning means <NUM>. The cleaning means <NUM> allows for using the ultrasound detection system <NUM> in harsh and dusty environment without risking detection efficiency to decrease during operation.

The cleaning means <NUM> comprises air blowing means having a pressurized air supply <NUM>. The air blowing means is fluidly connected to the ultrasonic transmitter 151a and the ultrasonic receiver 152a. The control unit <NUM> is adapted to control the pressurised air supply such as to inject pressurised air for keeping the ultrasonic transmitter 151a and the ultrasonic receiver 152a clean. The pressurized air may be injected as bursts occurring with regular time intervals. Alternatively, the pressurized air may be injected continuously. The control unit <NUM> may be adapted to control the flow of pressurized air through the conduits. This may be achieved by adjusting the air pressure of the pressurised air supply <NUM>. Alternatively, or additionally, it may be achieved by adjusting a cross section of the conduit for example using a throttle or a variable valve.

The ultrasonic detection system <NUM> further comprises a protective case 156a at least partly housing the ultrasonic transmitter 151a and the ultrasonic receiver 152a. One purpose of the protective case 156a is to protect the ultrasonic detection <NUM> from exposure from contaminants such as dirt or dust, both in wet and dry conditions. Another purpose of the protective case 156a is to control the spatial distribution of the transmitted ultrasonic signal 154a. This is achieved by the sound waves being reflected on an inner wall of the protective case 156a. The surface structure of the inner wall of the protective case 156a will be of importance. A rugged surface may result in back reflections, risking to affect the spatial distribution and/or penetration length of the transmitted ultrasonic signal 154a. Moreover, back reflections may result in deteriorated readings when detecting the ultrasonic signal 154a using the at least one ultrasonic receiver 152a. The details with regards to the cleaning of the ultrasound detections system will be further discussed later.

The at least one ultrasonic transmitter 151a and the at least one ultrasonic receiver 152a may be mounted inside the protective case 156a such as to form a single ultrasonic detection unit 150a. The ultrasonic detection unit 150a may be mounted onto a frame of the arrangement. The ultrasonic detection unit 150a may be translationally attached such as to allow adjusting the distance between the ultrasonic detection unit 150a and the surface 142a.

The arrangement <NUM> further comprises a second ultrasonic detection unit 150b adapted to measure properties pertaining to the middlemost screen deck 112b. The second ultrasonic detection unit 150b is arranged at a second surface 142b of the arrangement <NUM>. The second ultrasonic detection unit 150b is arranged to transmit ultrasonic signal 154b directed substantially horizontally such that the ultrasonic signal 154b hits the screening material present on the middlemost screen deck 112b from the side. The second ultrasonic detection unit 150b will detect an ultrasonic signal 154b predominately originating from reflections on the screening material <NUM>. Thus, it is understood that the second ultrasonic detection unit 150b provides different kind of information than the ultrasonic detection unit 150a, which may provide information from both the screening material and the surface 142a. The second ultrasonic detection unit 150b is connected to the control unit <NUM> and fluidly connected to the pressurised air supply <NUM>.

The ultrasound detection system is preferably being located in a non-vibrating position, for example on a supporting frame of the arrangement. This improves the reliability and durability of the system over time. The ultrasound detection system may, however, be arranged to vibrate with the arrangement. This may be an advantage in some applications where other detection means and/or detection angles are not adequate for the task.

<FIG> shows an arrangement <NUM> according to an example. This example is not part of the invention, but incorporated herein for providing an overall better understanding. The arrangement <NUM> comprises a feeder <NUM>. The feeder <NUM> is adapted to supply screening material <NUM> to a further device <NUM>, such as for example a crusher. The arrangement <NUM> comprises an ultrasonic detection system <NUM> similar to the ultrasonic detection system of <FIG>. The ultrasonic detection system <NUM> comprises an ultrasonic detection unit <NUM> arranged to detect the presence of oversized material that may risk getting jammed inside the further device <NUM>.

<FIG> shows an arrangement <NUM> according to another example. This example is also not part of the invention, but incorporated herein for providing an overall better understanding. The arrangement <NUM> comprises a chute <NUM>. The chute <NUM> is adapted to direct screening material <NUM> from one or more sources of screening material (in the example: two sources of screening material) to a conveyer belt <NUM>. The conveyer belt <NUM> is adapted to transport screening material <NUM> received from the chute <NUM> to a further device <NUM>, such as for example a crusher. The arrangement <NUM> comprises an ultrasonic detection system <NUM> similar to the ultrasonic detection system of <FIG>. Although the example embodiment in <FIG> shows a chute comprising dual inlets, it is understood that a single inlet chute may equally well be equipped with an ultrasonic detection system of the disclosure.

The ultrasonic detection system <NUM> comprises a first ultrasonic detection unit 350a arranged to measure inside a first fork 311a of the chute <NUM> and a second ultrasonic detection unit 350b arranged to measure inside a second fork 311b of the chute <NUM>. In the situation example shown in <FIG>, screening material has gotten jammed inside the first fork 311a of the chute <NUM> whereas the screening material is free to move through the second fork 311b of the chute <NUM>. Hence, the control unit <NUM> will obtain a different signal from the first ultrasonic detection unit 350a than from the second ultrasonic detection unit 350b. The control unit <NUM> may be operable to send out an alarm to inform about the jammed material inside the first fork 311a.

The ultrasonic detection system <NUM> further comprises a third ultrasonic detection unit 350c arranged to measure at a surface of the conveyor belt <NUM>. The purpose of the third ultrasonic detection unit 350c is similar to the purpose of the ultrasonic detection unit <NUM> of <FIG>, i.e. to detect larger pieces of screening material which risks getting jammed in the further device <NUM>. Another purpose of the third ultrasonic detection unit 350c can be to detect jams in other parts of the process upstream from where the third ultrasonic detection unit 350c is placed. For example, if screening material is expected to be on the conveyer <NUM>, but the third ultrasonic detection unit 350c does not detect the presence of material, it is likely to be a jam or other problem upstream, effectively hindering the material to enter the conveyer <NUM>.

The arrangement <NUM> comprises a cleaning means <NUM> similar to the cleaning means <NUM> for the arrangement <NUM> discussed herein. Specifically, the first 350a, second 350b and third 350c ultrasonic detection units are all fluidly connected to a pressurised air supply <NUM>. Moreover, the first 350a, second 350b and third 350c ultrasonic detection units are all connected to the control unit <NUM>.

The control unit <NUM> is adapted to control a cleaning process of the ultrasonic transmitters and/or the ultrasonic receivers of the first 350a, second 350b and third 350c ultrasonic detection units by means of the cleaning means <NUM>. The control unit <NUM> may be adapted to control the cleaning process differently for different ultrasonic detection units. For example, the first 350a and second 350b ultrasonic detection unit may be supplied with a continuous flow of pressurised air to establish an over pressure within the protective cases of the ultrasonic detection units, whereas the third ultrasonic detection unit 350c may be supplied with pressurised air at predefined time intervals.

<FIG> shows a cleaning detection system <NUM> in an arrangement for handling screening material, e.g. aggregate, ore or similar. The cleaning detection system <NUM> comprises an ultrasonic transmitter <NUM> arranged at a surface <NUM> of the arrangement, and adapted to send out an ultrasonic signal <NUM> towards the surface <NUM>, an ultrasonic receiver <NUM> arranged at the surface <NUM>, and adapted to receive the ultrasonic signal <NUM>, and a protective case <NUM> at least partly housing the at least one ultrasonic transmitter <NUM> and the at least one ultrasonic receiver <NUM>. The cleaning detection system <NUM> is characterised in that it further comprises a control unit 460a connected to the at least one ultrasonic transmitter <NUM> and the at least one ultrasonic receiver <NUM>, and adapted to detect a difference in at least one parameter based on a comparison between the ultrasonic signal <NUM> and a reference signal.

The cleaning detection system <NUM> further comprises cleaning means <NUM> arranged at the protective case <NUM>. The cleaning means <NUM> in turn comprises air blowing means adapted to clean the protective case <NUM>. The air blowing means comprises a nozzle <NUM> arranged inside the protective housing <NUM>. The nozzle <NUM> is fluidly connected to a pressurised air supply <NUM> by means of a conduit <NUM>. The cleaning means <NUM> is connected to a further control unit 460b configured to control the operation of the cleaning means <NUM> for initiating a cleaning of the protective case <NUM>. The further control unit 460b instructs the pressurised air supply <NUM> to supply pressurised air to the conduit <NUM> thus achieving a plume <NUM> of pressurised air to enter an interior portion of the protective housing <NUM>. In the embodiment shown in <FIG>, the nozzle <NUM> is shaped such as to supply the plume <NUM> of air in the direction of the ultrasonic transmitter <NUM> and the ultrasonic receiver <NUM>. The position of the nozzle <NUM> may be adjustable such as to allow optimizing the cleaning of the protective case <NUM> and should be such that it does not interfere with the signal from and to the ultrasonic transceiver. The direction of flow may however be different in other embodiments.

The ultrasonic transmitter <NUM> and the ultrasonic receiver <NUM> is constituted by one single element, wherein the single element comprises a piezo element. Thus, the ultrasonic transmitter <NUM> and the ultrasonic receiver <NUM> is comprised in one single unit.

The signal <NUM> may be sent out in a direction substantially perpendicular to the surface <NUM> of the arrangement. The at least one parameter may be constituted by a time period, a frequency, and/or an amplitude of the ultrasonic signal <NUM>.

The control unit 460a may be adapted to report that problem has been identified if the difference in the at least one parameter is outside of an acceptable interval.

As previously mentioned, the cleaning detection system <NUM> is a part of an arrangement for handling screening material, e.g. aggregate, ore or similar. Though not explicitly shown in <FIG>, such an arrangement may comprise a plant, a screen, a screening deck, a conveyor belt, a chute, a feed box or a discharge box.

<FIG> illustrates an arrangement <NUM> for handling screening material, e.g. aggregate, ore or similar, according to an example embodiment, which arrangement <NUM> comprising a bed depth detection system.

The arrangement <NUM> comprises a screen <NUM> comprising at least one screen deck <NUM>. The at least one screen deck <NUM> is attached to vibrating means (not shown) arranged to cause a vibration of the at least one screen deck <NUM>. The vibration causes the at least one screen deck <NUM> to be located at different positions at different times. Specifically, the vibration causes the at least one screen deck <NUM> to be located at different vertical positions for different times. The vibration means is not explicitly disclosed herein. It should be understood that many alternative ways exist for achieving said vibrations within the scope of the claims.

The screen <NUM> further comprises input means <NUM> arranged to input screening material onto the at least one screen <NUM>. For the screen <NUM>, the screening material <NUM> is input, via the input means <NUM>, onto the at least one screen <NUM>. The at least one screen deck <NUM> has a plurality of through holes covering a portion of its surface. As the at least one screen deck <NUM> vibrates, screening material <NUM> located thereon will be caused to move around. Pieces of the screening material <NUM> with dimensions smaller than the dimensions of the through holes are allowed to leave the at least one screen deck <NUM> via the plurality of through holes. Screening material with dimensions larger than the dimensions of the through holes of the at least one screen deck <NUM> is allowed to leave the at least one screen deck <NUM> at an end thereof, as illustrated in <FIG>.

The arrangement <NUM> further comprises a bed depth detection system for detecting a bed depth W of the screening material <NUM>. The bed depth detection system comprises an ultrasonic detection unit <NUM> and a control unit <NUM>.

The ultrasonic detection unit <NUM> comprises an ultrasonic transmitter <NUM> arranged at a part, here a surface <NUM>, of the arrangement <NUM> on or in relation to which the screening material is traveling, the ultrasonic transmitter <NUM> being adapted to send out an ultrasonic signal <NUM> towards the surface <NUM>. The ultrasonic detection unit <NUM> further comprises an ultrasonic receiver <NUM> being adapted to receive the ultrasonic signal <NUM>.

The control unit <NUM> is connected to the ultrasonic transmitter <NUM> and to the ultrasonic receiver <NUM>, and is adapted to calculate a bed depth W of the screening material <NUM> present on the surface <NUM> from a comparison between the ultrasonic signal <NUM> and a reference signal based on at least one parameter.

The bed depth detection system further comprises a cleaning means <NUM> connected to the control unit <NUM> and arranged at the ultrasonic transmitter <NUM> and the ultrasonic receiver <NUM>. The control unit <NUM> is adapted to control a cleaning process of the ultrasonic transmitter <NUM> and/or the ultrasonic receiver <NUM> by means of the cleaning means <NUM>. The cleaning means <NUM> allows for using the bed depth detection system in harsh and dusty environment without risking detection efficiency to decrease during operation.

The cleaning means <NUM> comprises air blowing means having a pressurized air supply <NUM>. The air blowing means is fluidly connected to the ultrasonic transmitter <NUM> and the ultrasonic receiver <NUM>. The control unit <NUM> is adapted to control the pressurised air supply such as to inject pressurised air for keeping the ultrasonic transmitter <NUM> and the ultrasonic receiver <NUM> clean. The pressurized air may be injected as bursts occurring with regular time intervals. Alternatively, the pressurized air may be injected continuously. The control unit <NUM> may be adapted to control the flow of pressurized air through the conduits. This may be achieved by adjusting the air pressure of the pressurised air supply <NUM>. Alternatively, or additionally, it may be achieved by adjusting the conduit cross section for example using a throttle or a variable valve.

In this specific embodiment, the ultrasonic transmitter <NUM> and the ultrasonic receiver <NUM> are constituted by one single piezo element, and the ultrasonic detection unit <NUM> is arranged such that the ultrasonic signal <NUM> is sent out in a direction substantially perpendicular to the surface <NUM> of the arrangement <NUM>.

As stated above, the bed depth detection system is used for detecting the bed depth W of the screening material <NUM>. A method for detecting a bed depth of a screening material <NUM> comprising the steps of sending out an ultrasonic signal <NUM> towards a surface <NUM> on or in relation to which the screening material is traveling, receiving the ultrasonic signal <NUM>, and calculating the bed depth W of the screening material <NUM> present on the surface <NUM> from a comparison between the ultrasonic signal <NUM> and a reference signal based on at least one parameter.

The method may further comprise conducting a specific action if the calculated bed depth W is outside of an acceptable interval.

There are numerous ways of calculating the bed depth W of the screen material <NUM> based on information from the ultrasonic detection unit <NUM>.

The at least one parameter may be constituted by a time period. In such a case, the bed depth detection system may be arranged to detect a distance to a target by determining a time delay between a time of transmitting and a time of receiving an ultrasonic signal <NUM> transmitted in a direction of the target. In this specific embodiment, the target is the material present on the surface <NUM>.

That time delay can thereafter be compared with the corresponding time delay determined in view of a reference signal, which reference signal has transmitted and received in the corresponding manner as described above but during ideal circumstances, for example when the arrangement <NUM> is not in operation or in operation but without load.

Based on the difference in time delay, the bed depth W of the screening material <NUM> or the size of the objects present on the surface of the arrangement <NUM> can be calculated by means of the control unit <NUM>.

Should the difference between the time period of the ultrasonic signal <NUM> and the reference signal deviate more than a predetermined error margin it can be concluded that there is an operating problem with the arrangement <NUM>.

Alternatively, the at least one parameter may be constituted by a frequency of the ultrasonic signal <NUM>. In such a case, the bed depth detection system may be arranged to detect a speed of a target with respect to the be depth detection system. The speed of the target may be calculated with knowledge of the speed of sound by utilizing the formulation of the Doppler effect for sound waves.

Alternatively, the at least one parameter may be constituted by an amplitude of the ultrasonic signal <NUM>.

Although discussed separately, any combination of the properties of time, frequency and amplitude may be used to achieve a purpose of the bed depth detection system. Other properties may also be used. For example, the spatial distribution of the signal <NUM> may be used to infer properties of the target. For such a case, the ultrasonic receiver <NUM> may comprise a spatially resolving sensor. Furthermore, the properties of the ultrasonic signal <NUM> transmitted by the ultrasonic transmitter <NUM> may be different depending on the purpose. For example, the signal may be pulsed or continuous. Furthermore, the base frequency of the ultrasonic signal <NUM> may vary dependent on the purpose.

The control unit <NUM> may be adapted to detect a difference in the at least one parameter based on a comparison between the ultrasonic signal <NUM> and a reference signal. The reference signal may be for example the signal detected by the control unit <NUM> in a case where no screening material <NUM> is affecting the signal <NUM>. For example, a reference signal may be recorded and stored when the arrangement <NUM> is not in operation or in operation without load. Alternatively, or additionally, a reference signal may be the signal detected by the control unit <NUM> for a specific position of a vibrating screen <NUM>. For example, the reference signal may be the signal detected by the control unit <NUM> when a screen deck <NUM> is unloaded in its default position.

By measuring the bed depth W of the screening material <NUM> on the screen <NUM> many important parameters related to the screening process can be calculated. These parameters can be used to optimize the process, investigate if the screen is overloaded, or underloaded, compared to specification, calculate and predict the wear life of screening media etc..

Several mathematical models exist for calculating the capacity for a given bed depth W. By using these mathematical models, the efficiency of the screen <NUM> can be calculated in order to find out how it is operating. This information can be used to optimize the screening process. For a given capacity it is also possible to give recommendations of a suitable bed depth W for the screen <NUM>. The system can give a warning if the bed depth is too high or too low compared to set levels.

The information can also be used to calculate the wear life of the screening media. It is always very important for the user to know how much screening material each screen deck <NUM> can handle before it has to be replaced. This means that the downtime for maintenance and replacement can be predicted and minimized to save money. This type of information is also vital so that the supplier can deliver screening media to the user exactly when it is needed. It is for example possible to use the system during planned downtime occasions, when the screen decks are free from screening material. By measuring the distance to the surface of the screening deck and compare readings over time, it is possible to determine how much the screening deck has been worn and knowing the initial thickness of the screening media, it is possible with a high degree of certainty to determine when it is time to replace screening media. Either all or only some of the screening media modules may be replaced at a same time. The information can be used to predict wear rate and wear life in both hours and tons and connect predicted wear with actual wear.

<FIG> illustrates the arrangement <NUM> for a purpose of monitoring the operation of the screen <NUM>. The screen <NUM> is here shown empty from any screening material <NUM>. It is however envisioned that screening material <NUM> may be present on the screen, at least to some extent. <FIG> aids to illustrate that the bed depth detection system may be used to monitor the movement of the at least one screen deck <NUM> in relation to the bed depth detection system. Specifically, the bed depth detection system may be used to measure the stroke of the vibrating at least one screen deck <NUM>. For the arrangement <NUM>, the stroke may be determined in the vertical dimension by detecting the distance between the bed depth detection system and the screen for different positions of the screen <NUM>. The maximum stroke in the vertical direction will be the difference between the maximum distance Dmax and the minimum distance Dmin. The bed depth detection system may also be used to detect temporal fluctuations in the vibrational motion of the at least one screen deck <NUM>.

A purpose of detecting the vibrational characteristics of the at least one screen deck <NUM> is to identify unwanted behaviour of the screen. One example of such an unwanted behaviour is when the screen deck <NUM> is vibrating at or close to an eigenfrequency of the at least one screen deck <NUM>, a situation which significantly increases the risk of introducing a screen malfunction. Another example concerns the influence of the screening material <NUM> on the vibrational characteristics. For example, if the screening material <NUM> present on the at least one screen deck <NUM> constitutes an excessive load and/or some pieces are of a dimension not expected, the stroke may be effected. This implies that the bed depth detection system may be used to measure on the screening material <NUM> indirectly as a result from the screening material <NUM> affecting the vibrational characteristics of the at least one screen <NUM>.

<FIG> illustrates an arrangement <NUM> for handling screening material, e.g. aggregate, ore or similar, according to an example embodiment, which comprises a mesh comprising a plurality of ultrasonic transmitters and ultrasonic receivers, respectively.

The arrangement <NUM> comprises a screen <NUM> having at least one screening deck <NUM>. The arrangement further comprises input means <NUM> arranged to input screening material onto the at least one screening deck <NUM>.

In this exemplifying embodiment, the arrangement <NUM> is provided with a mesh comprising six ultrasonic detection units <NUM>, each ultrasonic detection unit <NUM> comprising an ultrasonic transmitter <NUM> adapted to send out an ultrasonic signal <NUM> towards the surface <NUM> of the at least one screening deck <NUM>. Each ultrasonic detection unit <NUM> further comprises an ultrasonic receiver <NUM> adapted to receive the ultrasonic signal <NUM>. The ultrasonic detection units <NUM> are distributed over the surface of the screening deck <NUM>.

The control unit <NUM> is connected to each of the ultrasonic transmitters <NUM> and the ultrasonic receivers <NUM>, and is adapted to detect at least one parameter of the ultrasonic signal of each ultrasonic detection unit. An example of such a parameter is the bed depth W of the screening material <NUM> present on the surface <NUM>.

The control unit <NUM> may be adapted to detect a difference in the at least one parameter of the ultrasonic signal of each of the ultrasonic detection units based on a comparison between the respective ultrasonic signal <NUM> and a reference signal.

The control unit <NUM> may further be connected to a monitoring device <NUM> for monitoring the at least one parameter of the ultrasonic signal <NUM> of each of the ultrasonic detection units <NUM>. The parameter detected, for example the bed depth W, by each of the ultrasonic detection units <NUM> can thereby be monitored and followed in real time.

A method of monitoring the calculated bed depth, previously discussed in this disclosure, from ultrasonic signals from the mesh comprising a plurality of ultrasonic transmitters and receivers can provide a considerable amount of useful information. For example, when monitoring the calculated bed depth from ultrasonic signals from portions at left and right hand sides of the surface of a screening deck of the arrangement, it may be detected that one of the signals provides a higher calculated bed depth than the other. If a value of the calculated bed depth is continuously larger for one signal, this suggests there is a non-uniform material distribution on the screening deck, and thus a poor feed distribution of the material. If the monitored value of the calculated bed depth is near a pre-set upper limit, this suggests that the screening deck at least at the corresponding portion of the surface is overloaded.

If a value of the calculated bed depth varies significantly, this may suggest that the ultrasonic signal does not hit the surface it is set to measure perpendicularly resulting in an echo of the signal. It can thus be deduced that the screen is tilting, for example due to a missing spring or other support structure of the screen.

<FIG> illustrates an example embodiment of a part of an ultrasonic detection system in an arrangement <NUM> comprising at least one reflector <NUM>. The illustrated arrangement <NUM> comprises at least one screen deck <NUM>. The arrangement further comprises a screen wall <NUM> at an end of the screen deck <NUM>.

The arrangement <NUM> further comprises an ultrasonic detection unit <NUM> arranged at the screen wall <NUM>. The ultrasonic detection unit <NUM> may, however, be arranged at another position of the arrangement. The ultrasonic detection unit <NUM> comprises an ultrasonic transmitter <NUM> adapted to send out an ultrasonic signal <NUM> in a horizontal plane, and an ultrasonic receiver <NUM> adapted to receive the ultrasonic signal <NUM>. The ultrasonic detection unit <NUM> further comprises a reflector <NUM>, arranged at or close to the at least one screen deck <NUM>, and horizontally at a distance of the ultrasonic detection unit <NUM>. The reflector <NUM> is, in this exemplifying embodiment, arranged at an angle of <NUM>° with respect to the horizontal plane, such that it can deflect the ultrasonic signal <NUM> from the ultrasonic transmitter <NUM> towards the screen deck <NUM>. Correspondingly, the reflector can deflect the ultrasonic signal <NUM> reflected back from the screening deck towards the ultrasonic receiver <NUM>. The reflector thus allows deflecting the ultrasonic signal <NUM> towards a surface which is vertical to the plane in which the ultrasonic detection unit <NUM> is arranged.

By arranging the reflector in different angles, the ultrasonic signal <NUM> can be deflected towards surfaces at different angles from the plane of the ultrasonic detection unit <NUM>. The reflector thus provides the advantage of enabling access for the ultrasonic signal to locations of the arrangement <NUM> which are hard to reach due to lack of space or structures for mounting the ultrasonic transmitter and the ultrasonic receiver, or to harsh operating conditions.

The skilled person realizes that a number of modifications of the embodiments described herein are possible without departing from the scope of the invention, which is defined in the appended claims. For example, it is also possible to arrange sensors behind the screen deck for making measurements between or below a screen deck. It would thereby be possible to measure the density, or with other words the amount of material which falls from a screen deck, thus deducing the tonnage per time unit. A stronger echo would imply more material passing through the screening deck whereas a weaker echo would imply less material passing through. This could then be evaluated as to how much material passing through a given screen deck in relation to a theoretical content of undersize particle in the material fed to the screening arrangement. The information thus obtained could be used to evaluate the distribution of screening material load per screen deck, but also for estimation of screening efficiency. It also provides information as to how plugged a screen deck has become in comparison with a fully open screen deck.

Claim 1:
An arrangement (<NUM>) for handling screening material (<NUM>), e.g. aggregate, ore or similar, said arrangement (<NUM>) comprising a screening deck (<NUM>) on or in relation to which screening material is traveling, the arrangement (<NUM>) further comprising an ultrasonic detection system (<NUM>) comprising:
an ultrasonic transmitter (151a) arranged at the arrangement (<NUM>), and adapted to send out an ultrasonic signal (154a) towards a surface (142a),
an ultrasonic receiver (152a) adapted to receive the ultrasonic signal (154a), and
a control unit (<NUM>) connected to the ultrasonic transmitter (151a) and the ultrasonic receiver (152a), the control unit (<NUM>) being adapted to detect at least one parameter of the ultrasonic signal (154a),
wherein the control unit (<NUM>) further is adapted to detect a difference in the at least one parameter based on a comparison between the ultrasonic signal (154a) and a reference signal,
wherein the ultrasonic detection system further comprises:
a reflector arranged for deflecting the ultrasonic signal towards the surface of the screening deck (<NUM>) of the arrangement (<NUM>), and
a mesh which comprises a plurality of ultrasonic transmitters and ultrasonic receivers wherein each ultrasonic transmitter and ultrasonic receiver is arranged over the surface of the screening deck (<NUM>) of the arrangement (<NUM>).