A vibrating apparatus system with a perforated screen element and a computer implemented method for providing an alarm signal. The present invention relates to a vibrating apparatus system, com prising a vibrating apparatus, such as a sieve apparatus or a transporting fluid bed apparatus, and a data processing unit, wherein the vibrating apparatus comprises a frame and a perforated screen element suspended in the frame; the perforated screen element comprising a first end and a second end, the perforated screen element having a longitudinal extent between the first end and the second end; the frame comprising fastening devices for fastening the first end and the second end, respectively, of the perforated screen element; and at least one of said fastening devices being movable relative to a main portion of the frame and a power element being provided for effecting said one of the fastening devices to apply a longitudinal tension to the perforated screen element in a direction of the longitudinal extent thereof.

WO 2016/037620 A1 discloses an example of a vibrating apparatus of the above kind in the form of a sieve apparatus.

As used herein, the term 'data processing unit' is intended to comprise any circuit and/or device suitably adapted to perform the functions described herein. In particular, the above term comprises general purpose or proprietary programmable microprocessors, Digital Signal Processors (DSP), Application Specific Integrated Circuits (ASIC), Programmable Logic Arrays (PLA), Field Programmable Gate Arrays (FPGA), special-purpose electronic circuits, etc., or a combination thereof.

Further, as used herein, the term ‘fluid bed apparatus’ and the synon ymous ‘fluidized bed apparatus’ are intended to comprise an apparatus having a compartment with a perforated bottom and means for providing a gas flow, e.g. an air flow, through the perforated bottom to aerate and/or suspend a par- ticulate material in a rising gas flow inside the compartment to keep the partic- ulate material in a fluidized or fluid-like condition in which the particulate mate rial behaves mainly as a fluid.

In vibrating apparatuses comprising a perforates screen generally comprises few wearing parts and generally have long service lives, but a known problem is that the perforated screen element is subject to wear and rupture of the screen is a risk. Such rupture may result in material, which should have passed over the screen without passing through the screen, actually passing through the screen. E.g. in case of a sieving apparatus the pursued product of a sieving process may be fine material that has passed through the screen, and in case of a rupture of the screen said product may be contaminated by coarse material that unintendedly passes through the screen with the result that the product has to be sieved once again or discarded. In another case the product of a sieving process may be a material void of a fine fraction that passes through the screen and in such case a rupture may result in part of the pursued product passing unintendedly through the screen resulting in a loss of product.

Sieving is used in many fields and industries including, but not limited to dairy, brewing, chemical, food, pharma and pet food industries, etc.

Rupture of a screen may appear in different ways. The screen may burst more or less completely within a short period of time, which may be rela tively easily observed or a small rupture may appear that will gradually grow larger.

A number of prior art systems for detecting a rupture of a screen in a sieving apparatus are known.

Thus, CN 101884977 A discloses an apparatus for registration of the out flow of coarse material from a sieving apparatus. When the out flow of the coarse material unexpected halts this is registered as an indication of the screen having been ruptured. This prior art system will however not register small ruptures, because small ruptures may not provide a signal substantially different from normal fluctuations of the out flow of the coarse material.

US 2009/0000994 A1 discloses a system for detecting sieve breakage in which the screen comprises conductive threads and an electric current is lead through said conductive threads. In case of a rupture, even a relatively small rupture, conductive threads will be broken resulting in a measurable change of electrical resistance. However, for some processes the material to be sieved comprises inflammable material part if which may be in the form of dust. Such inflammable dust may cause a powder explosion when subject to an electric spark as might occur in case of rupture of an electrical conductor. Obviously the system disclosed in US 2009/0000994 A1 has limitations in re spect of applicability.

It is an object of the present invention to provide a vibrating apparatus system of the kind mentioned by way of introduction with a system for detecting a rupture of the perforated screen element avoiding the above mentioned short comings of the prior art.

This is obtained by the invention in that the vibrating apparatus further comprises a position sensor being configured to establish a relative position of a position element, one of the position sensor, and the position element being connected to said movable fastening device, and said at least one position sen sor being communicatively connected to the data processing unit, where the data processing unit is configured to register variations over time of said relative position.

Thus, one of the position sensor and the position element may be at tached to a stationary part of the apparatus, while the other of the position sen sor and the position element may be attached to a part which is moved relative to the stationary part when longitudinal tension is applied to the perforated screen.

The position sensor and the position element may be regarded com monly as a position sensor aggregate and may e.g. be included in a standard product such as a pneumatic or hydraulic cylinder which thus may provide an indication of a current extent of a piston rod of the pneumatic or hydraulic cyl inder when the piston rod is extended and retracted.

In an embodiment, variations of said relative position with an amplitude down to 0.01 mm are registered. Further, variations of said relative position with an amplitude in an interval of 0.01 mm to 10 cm may be registered. The system may be said to be configured to measure a parameter indicative of the longitudinal extent of the perforated screen element whereby a variation of said parameter is indicative of a variation of the longitudinal extent of the perforated screen element.

The mentioned relative position of the position element may e.g. be in relation to a point fixed relative to the main portion of the frame and/or in relation to the position sensor.

The present invention considers that in case of a rupture of the perfo rated screen element or a failure of the fastening of one of the ends of the perforated screen element by the respective fastening device a, possibly minor, variation of the longitudinal extent of the perforated screen element between the fastening devices will be observable.

It should be noted that it is possible to use more than one position sensor aggregate to registre variations of relative positions over time, e.g. of different elements or locations on elements of the apparatus relating to the lon gitudinal extent of the perforeted screen.

During operation of an apparatus of the above mentioned kind the tem perature will vary e.g. due to friction between various parts and due to varia tions of the temperature of the surroundings and variations of the process tem perature. Such temperature variations may entail variations of the longitudinal extent of the perforated screen element and such variations of the longitudinal extent of the perforated screen element will be normal.

Thus, according to an embodiment the data processing unit is config ured to provide an alarm signal when registering an abnormal variation over time of the relative position of the position element.

In an embodiment the abnormal variation over time is a positional shift of a distance exceeding a predetermined value.

In an embodiment the abnormal variation over time is a positional shift of a distance per time unit exceeding a predetermined value.

In an embodiment the abnormal variation over time is an abrupt change over time.

In a practical embodiment said position element is one of: an item fixedly attached to the end of the perforated screen element attached to said movable fastening device; an item fixedly attached to the said movable fastening device; and a first portion of said power element. Hereby it is possible to measure if the longitudinal extent of the perforated screen element is subject to a change.

In an embodiment the vibrating apparatus has an inlet section with a feed inlet for material and a discharge section with at least one outlet. In a further embodiment the first end of the perforated screen element is provided at the inlet section and the second end of the perforated screen element is provided at the discharge section. In yet a further embodiment the at least one movable fastening device is provided at the discharge section.

Over time the relative position of the position element will change due to positional shifts of the position element and by registering such positional shifts and regularly inspecting the perforated screen element for possible rup tures, knowledge for the system may be gained about normal positional shifts i.e. positional shifts occurring during normal operation without ruptures of the perforated screen element occurring. The positional shifts may e.g. be regis tered as a size of a distance of the shift from a resting position, and as a dis tance per time unit i.e. as a speed of the positional shift.

In an embodiment the vibrating apparatus system further comprises a temperature sensor, where the temperature sensor is communicatively con nectable to the data processing unit, where the data processing unit is config ured to register the temperature change over time of the vibrating apparatus and compare it to the registered variations over time of said relative position. Changes of the extent of the perforated screen element may be due to temper ature variations occurring during operation or subject to variations of surround ings temperature. Thus knowledge of current temperature may be taken into consideration for defining the normal variations. Thereby it may be possible to reduce a number of false alarms.

In an embodiment the data processing unit is communicatively con nectable to a user device, and configured for providing an alarm signal to said user device.

The object of the invention is also obtained by a computer imple mented method for providing an alarm signal regarding an abnormal variation over time of a longitudinal extent of a perforated screen element of a vibrating apparatus, wherein the vibrating apparatus comprises a frame, a perforated screen element suspended in the frame and a position sensor; the perforated screen element comprising a first end and a second end, the perforated screen element having a longitudinal extent between the first end and the second end; the frame comprising fastening devices for fastening the first end and the second end, respectively, of the perforated screen element; at least one of said fastening devices being movable relative to a main portion of the frame and a power element being provided for effecting said one of the fastening devices to apply a longitudinal tension to the perforated screen element in the direction of the longitudinal extent thereof, where the position sensor is configured to establish a relative position of a position element connected to said movable fastening device, the method comprising the steps of;

- receiving position signals from the position sensor; - determining, from the received position signals, if there is an abnor mal variation over time of said relative position.

In an embodiment the computer implemented method comprises providing an alarm signal if there is an abnormal variation over time of said relative position. In a further embodiment of the computer implemented method, the vi brating apparatus system further comprises a temperature sensor, the temper ature sensor being configured for sensing a temperature change over time of the vibrating apparatus, and the method further comprises the steps of;

- receiving temperature signals from the temperature sensor; - comparing the temperature signals with the position signals; and wherein the step of determining further comprises, - determining, from the received position signals and the received tem perature signals, if there is an abnormal variation over time of the longitudinal extent of the perforated screen element.

Vibrating apparatuses according to the present invention such as e.g. sieve apparatuses or transporting fluid bed apparatuses, may as mentioned be used in many different fields and industries, e.g. dairy, brewing, chemical, food, and pet food industries, etc. where hygienic conditions are an issue. In general, the apparatus should provide for good hygiene and the apparatus should not risk producing sparks during operation due to the risk of explosion when dusty or fluidized inflammable products are processed. The apparatuses according to the invention may be constructed in different scales and may e.g. be config ured to process amounts varying from approximately 100 kg/h to approximately 14,000 kg/h.

Vibrations applied to the vibrating apparatus may e.g. be in the range of 12-70 Hz and with an amplitude in the range of 1-15 mm.

In the following the invention will be explained in further detail by way of non-limiting examples of embodiments having reference to the accompany ing schematic drawings, in which

Fig. 1 illustrates an embodiment of a sieve apparatus according to the invention;

Fig. 2 shows a power element of the apparatus of Fig. 1 ;

Fig. 3 shows a detail of another embodiment sieve apparatus; and Figs. 4 to 6 are photographs illustrating different kinds of ruptures of a perfo rated screen element.

Referring to Fig. 1 showing a first embodiment of the invention, a sieve apparatus 1 comprises a frame or housing 2 having an inlet section with a feed inlet 3 for material to be sifted and a discharge section including at least one outlet 5, 7, and at least one substantially vertical side wall 9. In the embodiment shown, the housing 2 has a generally rectangular configuration as seen from above, and two opposing side walls 9 are present. The housing thus defines a general longitudinal direction between the inlet section and the discharge sec tion. A perforated screen element 11 having a longitudinal extension and being supported by a support structure 13,15 is present in the housing 2. The sieve apparatus 1 furthermore comprises means 17 for vibrating the perforated screen element, here a motor or electromagnetic vibrator providing a well-de fined frequency. Further details shown in Fig. 1 include means 19 for tightening the perforated screen element 11 in the longitudinal direction, parts of a carry ing structure 21 including spring means for the vibration function (not shown), and inspection covers 23.

Thus a vibrating apparatus system of the invention, comprises a vi brating apparatus, such as the sieve apparatus 1 shown in Fig. 1 , or a trans porting fluid bed apparatus, and a data processing unit 25 as indicated in Fig. 2, wherein the vibrating apparatus comprises a frame, such as the housing 2 of Fig. 1 , and the perforated screen element 11 is suspended in the frame. In the present embodiment the perforated screen element 11 has a first end 12a at the inlet section and a second end 12b at the discharge section. The perfo rated screen element 11 has a longitudinal extent between the first end 12a and the second end 12b. The longitudinal extent of the perforated screen ele ment may be between 0.6 and 20 m or e.g. up to 3 m.

While Fig. 1 shows a sieve apparatus 1 with a single perforated screen element 11 , Fig. 3 shows, as an example of a sieve apparatus with multiple stages of perforated elements, a detail of a discharge section of a sieve appa ratus with two perforated screen elements 11a and 11 b positioned one above the other. It should be understood that Fig. 3 shows the apparatus with parts cut away to show interior as well as exterior details. Whereas the sieving ap paratus shown in Fig. 1 has two outlets 5, 7 the sieve apparatus of fig. 3 has three outlets 5, 6, 7.

In general, the frame or housing 2 comprises fastening devices as in dicated by 20a, and 20b for fastening the first end 12a and the second end 12b, respectively, of the perforated screen element 11 , and at least one of said fas tening devices 20a is movable relative to a main portion of the frame. A power element 33 is provided for effecting said one of the fastening devices 20b to apply a longitudinal tension to the perforated screen element 11 in a direction of the longitudinal extent thereof. Thus the fastening device 20b, including the power element 33, provides the means 19 for tightening the perforated screen element 11 in the longitudinal direction.

The frame or housing 2 may be open or it may be closed. Especially when a dusty product is to be processed, preferably an apparatus is used which comprises a closed frame or housing 2.

Examples of the fastening devices and power element are shown in Fig. 1 and more details are shown in Fig. 3. Thus, in the embodiments shown, the fastening devices comprise a cylinder 27 carrying pegs 29 to extend through apertures in the perforated screen element. The movable fastening de vice 20b is in the embodiments shown in Figs. 1 and 3 provided at the discharge section and is provided in that the cylinder 27 is rotatable. Applying a moment of force to the cylinder 27 in the counter-clockwise direction, as seen in Figs. 1 and 3, will apply a longitudinal tension to the perforated screen element 11 , 11a, 11 b. To apply such moment of force to the cylinder 27, in the embodiments shown, an inner end of an arm 31 is attached to the cylinder 27, and a power element 33, such as a pneumatic cylinder 33a (see Fig. 2) or a spring mecha nism 33b (see Fig. 3 is provided to apply a force to an outer end of the arm 31 opposite the inner end thereof. Thus it is seen that in the present embodiments the movable fastening device 20b is provided by the cylinder 27 with the pegs 29, the arm 31 and the power element 33. The fastening device 20a, which is not shown in detail, may comprise pegs, like the pegs 29, mounted in the frame 2 in any suitable manner. The pneumatic cylinder 33a and the spring mecha nism 33b respectively comprise a rod 35a, 35b and in order to apply a moment of force to the respective cylinder 27 the rod 35a is extended from the pneu matic cylinder 33a and the rod 35b is retracted by the spring mechanism 33b. As an example, an embodiment of a pneumatic cylinder 33a is shown in Fig. 2. The pneumatic cylinder 33a may e.g. be supplied with a pneumatic medium at a pressure of 2-8 bar.

According to the invention a position sensor is provided and configured to establish a relative position of a position element e.g. connected to said mov able fastening device, and said at least one position sensor is communicatively connected to the data processing unit 25, where the data processing unit is configured to register variations over time of said relative position.

Thus, in the embodiment shown a position sensor 37 is shown to be attached to the pneumatic cylinder 33a and is configured to establish the rela tive position of a position element 39 connected to the rod 35a. The position sensor 37 is communicatively connected to the data processing unit 25 as in dicated by broken line 41 .

During operation, the apparatus, including the frame or housing 2, the perforated screen element 11 , and the fastening devices, is vibrated by means of the motor 17, and a longitudinal tension is applied to the perforated screen element 11 by means of the power element 33. Variations of the longitudinal extent of the perforated screen element 11 over time is monitored and regis tered by the data processing unit 25 in that positional shifts of the position ele ment 39 registered by the position sensor 37 is registered and regarded as representative for the variations of said longitudinal extent.

Variations of the longitudinal extent of the perforated screen element 11 over time will naturally occur during operation, e.g. due to temperature var iations due to frictional heat and variation of the surrounding’s temperature. The system will over time learn to recognise such natural or normal variations of the longitudinal extent of the perforated screen element. In an embodiment the data processing unit 25 is configured to provide an alarm signal when registering an abnormal variation over time of the longitudinal extent of the perforated screen element 11 . Such abnormal variations might indicate that a rupture of the per forated screen element 11 has occurred.

In the present embodiment the position element 39 attached to the rod 35a and is thus provided as a portion of the power element 33.

In alternative embodiments the position element may e.g. be consti tuted by an item fixedly attached to the end of the perforated screen element attached to said movable fastening device; or by an item fixedly attached to the said movable fastening device.

The abnormal variation over time, that may trigger the data processing unit 25 to provide an alarm signal, is in an embodiment a positional shift of a distance exceeding a predetermined value. The abnormal variation over time, that may trigger the data processing unit 25 to provide an alarm signal, is in an alternative or additional embodiment a positional shift of a distance per time unit exceeding a predetermined value.

Thus in an embodiment the abnormal variation over time, that may trigger the data processing unit 25 to provide an alarm signal, is an abrupt change over time.

The perforated screen element 11 may be embodied in any manner known in the art. E.g. the perforated screen element 11 may comprise a screen mesh 43 provided of a thread material e.g. a metal thread material such as stainless steel, of. Figs. 4 to 6. The screen mesh 43 may be attached to edge elements 45 of sheet material, e.g. metal sheet material such as stainless steel, at the first and the second end of the perforated screen element 11. The edge elements 45 may comprise apertures 47 for receiving the pegs 29 extending form the cylinders 27 when mounting the perforated screen element 11 .

Different types of rupture of the perforated screen element 11 may oc cur, examples being indicated in Figs. 4 to 6. E.g. as shown in Fig. 4 the mate rial surrounding the apertures 47 may yield; threads of the screen mesh 43 may break as indicated at 49 in Fig. 5; or the screen mesh 43 may be torn from the edge element 45 as indicated at 51 in Fig. 6.

In an embodiment the apparatus comprises a temperature sensor 53 communicatively connected to the data processing unit 25 as indicated by bro ken line 55. In this embodiment the data processing unit 25 is configured to register the temperature change over time of the sieve apparatus and compare it to the registered variations over time of the relative position of the position element 39.

The data processing unit 25 may be communicatively connectable to a user device 57, e.g. a smart phone or another data processing unit, as indi cated by broken line 59. Thus the data processing unit may be configured for providing an alarm signal to the user device 57, e.g. if an abnormal variation over time of the longitudinal extent of the perforated screen element 11 is reg istered by the data processing unit 25.