FI92771C - Method and apparatus for transmitting a measurement signal from a rotating drum or equivalent to stationary receiving devices - Google Patents

Description

92771

Method and apparatus for transmitting a measurement signal from a rotating roller or the like to fixed receiving devices Forfarande och anordning f6r overforing av en måtsignal från en roterande Vals eller motsvarande till stationåra 5 mottagningsanordningar

The invention relates to a method for transmitting an analog measuring signal wirelessly from a roller or the like to separately separate receiving devices, the method using a measuring sensor or a series of measuring sensors, the signal of which is provided to a signal transmitter or to a transmitter. an analog signal or equivalent signal series proportional to the output signal from the sensor or sensor array, from which the analog measurement signal or signal array from the sensor or sensor array is applied to a voltage-to-frequency conversion unit whose frequency-modulated output and control the light beams of said transmitters are received by a light detector.

The invention further relates to a device for transmitting a measurement signal from a rotating roller or the like to separate receiving devices, in which device an analog measuring signal transmitter unit is arranged in connection with a rotating roller or the like, and a rotating roller or the like.

. a receiving unit for receiving a measurement signal or a series thereof transmitted wirelessly from a transmitter device is arranged in the immediate vicinity, which transmitter device comprises a voltage-frequency conversion unit, the input or inputs of which are connected to an analog measurement signal and a measurement signal series, an optical transmitter device, the receiving unit comprising a light detector connected to the input of a preamplifier.

Several different solutions are used to transmit the signal from the rotating roller. Known methods include various slip rings and signal transmission by radio. However, the slip rings are sensitive to heat and typically require a lot of free space on the roll shaft. Radio equipment is commercially available, but is intended primarily for transmitting the results of tax temperature measurements of signals from strain gauges, where the signals to be transmitted are typically in the order of a maximum of tens of millivolts.

With regard to the state of the art most closely related to the invention, reference is made to patent application EP-A1 0075620, which discloses a method and device as defined at the beginning for transmitting a temperature measurement signal from a rotating roller to separate receiving devices. It is an object of this invention to further develop the previously known method and apparatus of 10 of these publications in order to achieve more specifically defined objectives.

From the point of view of the yield and control of the papermaking process, it is important to know the distribution of the nip force both in the machine direction and in the cross direction.

With previously known methods and devices, it has been almost impossible to measure nip force and pressure during a production run.

The general object of the invention is to provide such a teletretrimeter 1-20 må and apparatus, in particular for transmitting analog signals from a water power roller to fixed receiving devices, so that the above-mentioned disadvantages are substantially avoided.

It is a further object of the invention to provide a telemetry method and apparatus suitable for measuring the nip pressures of rotating rollers and their distributions in different directions, for measuring the temperature states of the rolls and their distributions, and for measuring the displacements or deflections of the rolls.

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It is a further object of the invention to provide a telemetry method which allows η. To a measurement accuracy of 1% without the need to go to the coding of measurement signals, which complicates the measuring devices.

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It is a further object of the invention to provide a new method and apparatus for transmitting a measurement signal, in particular from a press roll, calender roll or winder roll used in papermaking, to fixed receiving devices, so that the method and device are simple and trouble-free.

It is a further object of the invention to provide a method and apparatus suitable for use in measuring the machine direction and / or transverse nip pressure and / or temperature-space distribution of nips used in papermaking, using a sensor comprising a plurality of sensors.

It is a further object of the invention to provide a telemetry method and apparatus for transmitting an analog signal from a rotating roller which is compact in design! and compact and low power consumption so that the device can be battery operated if necessary and implemented with commercially available standard components.

It is a further object of the invention to provide such a telemetry method which can advantageously transmit volt-level signals without interference.

It is a further object of the invention to provide a method and apparatus which is suitable for very demanding process conditions such as a paper machine.

In order to achieve the above and later objectives, the method of the invention is mainly characterized in that the light detector signal is directed to a frequency-to-voltage conversion unit from which the output signal or signal series is proportional to the measurement signal or signal series. to a series of light emitters which are connected in parallel with each other and that the light beams of said light emitters are directed alternately to be wiped at the sight of the light detector of a receiver arranged close to the light emitters.

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The device according to the invention, in turn, is mainly characterized in that the output of said preamplifier is connected to the input of a frequency-voltage conversion unit, that an analog signal or signal series corresponding to that the light transmitters are a series of light transmitters connected to the axis of the rotating roller, that a receiving unit is arranged near said axis so that the light beams of said light transmitters alternately sweep the signal from the light field of the receiving unit so that the field of view is 10

In the following, the invention will be described in detail with reference to some application examples of the invention shown in the figures of the accompanying drawing, to the details of which the invention is in no way narrowly limited.

Figure 1 schematically shows a press nip in which the invention can be applied.

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Fig. 2 schematically shows the distribution of the compression pressure in the press nip according to Fig. 1 in the machine direction.

Fig. 3 schematically shows the distribution of the compression pressure in the nip according to Fig. 1 in the transverse direction.

Figure 4 shows schematically and partly in block diagram form the main principle of the measuring arrangement according to the invention.

Figure 5 schematically shows a preferred implementation of the telemetry method according to the invention.

Fig. 6 shows, in connection with Fig. 5, the arrangement of the optical transmitters in connection with the roller shaft.

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Figure 1 schematically shows the press nip N of a dewatering press formed between the rollers 10 and 13. The dewatered web W is introduced into the nip N by means of a press felt 12. The upper roll 10 has an elastic coating 11 with a smooth outer surface 10 '. The lower roll 13 5 has a hollow surface 13 'into which water can escape from the press felt 12.

Figure 2 schematically shows the distribution of the compression pressure pM of the compression nip N in the machine direction 1. The compression pressure Pm has a peak value pmax. The nip N according to Fig. 1 may also represent a calendering nip, in which case the pressing felt 12 is of course not used and in which e.g. roll 13 is a hard surface roll and roll 10 is a calendering roll with a soft coating, e.g. polyurethane coating 11, so that nip N is so-called. soft calendering nip.

Figure 3 illustrates the transverse distribution of the compression pressure pT of the nip N, i.e. in the axial direction of the rollers 10 and 13. The transverse widths of the paper web W and the nip N are denoted by l ^.

The transverse distribution of the compression pressure pT in the dewatering crosses affects the dry matter content of the web, the distributions of web caliber and smoothness in the calendering nipples, and the uniformity, tension and hardness profile of the roll in the winding nipples. These are important process quantities, so the distributions of nip forces and pressures, pH and pT, are important parameters for the yield and control of the papermaking process.

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Figure 4 schematically shows the main principles of the measurement arrangement. A roll 20 of measuring sensors 201 ... 20n, which are thus provided, is arranged inside the coating 11 on a roll 10 formed by a pressing nip N and provided with an elastic, e.g. polyurethane coating 11. 30 n pcs. With the sensor set 20, both the machine direction nip pressure distribution p * and the transverse nip pressure distribution pT can be measured at the latter point in the transverse direction. The sensors 20 ^ .. 20 ,, are preferably evenly distributed and usually have n - 3-10 units. The sensors 20 can be attached either directly to the body of the roll 10 or inside the coatings 11 35, e.g. between its layers, or in some exceptional cases directly to the outer surface of the roll.

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The measurement signals from the sensors 20 are applied via cables 21 to a preamplifier 22, from which the gold sensor 20 has its own. With the preamplifiers 22, the signals are scaled to a suitable voltage level and applied to the switch unit 23. The switch unit 23 is controlled by a pulse sensor 25 so that once the +1 closes.

In Fig. 4, the switch 242 is closed and the other switches 24 are open, so that the measurement signal of the sensor 24z is further routed to the telemetry transmitter 26. The telemetry transmitter 26 is an optical transmitter whose signal K is wirelessly routed to the telemetry receiver 30 from each telemetry receiver. 20t 15 in the sequence of the measurement signal Vout id- l ... n). When the entire sensor array 20i has been run through, the next measurement sequence is started.

An essential feature of the above measurement arrangement is that only one telemetry channel is required, which essentially simplifies the system. The unit 15 connected to the roller 10, which comprises the amplifiers 22, the switching units 23 and the telemetry transmitter 26, can be implemented as a rather small battery-powered module, where, for example, the switching unit 23 is a standard integrated circuit. The pulse sensor 25 is preferably a photodetector with a filter, which detects, for example, the intensity of a LED with 25 narrow beams. The measuring unit 15 with power transmitters is placed on a rotating roller, e.g. on its shaft 14, preferably at the end of the shaft.

The sensors 20 are preferably made of a PVDF film, which is a piezoelectric film. With regard to the structure and operation of this film, reference is made to the journal article Processor 13/88, J. Koriseva: "Piezoelectric alternative". Suitable for the purposes of the invention are, for example, films sold under the trademarks "SOLEF" and "KYNAR", the thicknesses of which vary from 8 to 40 .mu.m. The PVDF membrane is well suited as a sensor, since only a force of tens of N 35 can already give the output voltage at the volt level.

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The measurement of nip pressure distributions ρ „and pT has been described above only as an example of an application environment of a telemetry arrangement according to the present invention. It should be emphasized that the telemetry arrangement of the invention can also be applied to the measurement of non-nip pressures, e.g. , such as slip rings or the like.

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The essential features of the telernetr method according to the invention and some preferred application examples will now be described with reference to Figures 5 and 6.

The transmitter unit 26 shown in Fig. 5 comprises a voltage-frequency conversion unit 16 with which the signal Vln to be transmitted from the rotating roller 10 is supplied. In Fig. 5, the signal Vln corresponds to the signal obtained in Fig. 4 as the output signal of the switch unit 23. The conversion unit 16 can be implemented in a commercially available microcircuit, which is e.g. LM 331 N. The output of the conversion unit 16 is connected by cables 18 to a series of light transmitters 17 ^ .. 17p. The transmitter unit 26 is in connection with the rotating roller 10. Valolåhet-timinā 17 is used, for example, in ice. The modulation frequency f is in the order of 1 ... 100 kHz. The series 171 ... 17p of the light transmitters 17 are mounted, e.g.

A receiver unit 30 is arranged near the shaft 14, the structure of which is shown in Fig. 5. The light beam of each light transmitter 17. Kp sweeps the light detector 32 of the receiver 30 alternately. In this way, the frequency-modulated measurement signal Vin is continuously transmitted.

As shown in Figure 5, the receiving unit 30 comprises a stained glass filter and a lens 31 which directs the light beams K to a light detector 32, which is preferably a photodiode, e.g. a Centronic OSD 50-0. The frequency modulated signal converted into an electrical signal by the photodetector 32 is applied to a preamplifier 33, which is e.g. OPA 620, by which the output of the photodetector 32 35 is scaled to suit the frequency-voltage converter 34. The preamplifier 33 is connected to a frequency / voltage converter 34, which is e.g. LM 2917 N. Thus 92771 8 a telemetry connection is provided, the analog output signal Vout of which is directly proportional to the analog input signal Vin.

In the application example according to Fig. 6, high-intensity LEDs 17 with the largest possible opening angle are used. In the receiving unit 30, light is collected by a lens 37 and the backlight is filtered by a narrowband filter. Lens 37 is a lens with the shortest focal length as wide an angle as possible (e.g. a so-called Fresnel lens).

In the arrangement according to Fig. 6, all the LEDs (n) of the telemetry transmitter 26 are modulated simultaneously at the same frequency so that there is always one LED 17A in the field of view of the receiver 30 (LED 172 in Fig. 6).

A preferred embodiment of the structure of the sensors 20 and their arrangement is shown in FI Patent Application No. 914829, which is filed simultaneously with this application, to which we refer in this respect.

The measurement signal Vout is applied to suitable display devices, e.g., display terminals, which graphically represent the distribution of the compression pressure pM and pT and / or other measuring variables useful in controlling and yielding a process using a rotating roller 10 or the like. The measurement signals Vout or the signals derived therefrom can also be combined with the transmission system of a paper machine or post-processing device such as a calender or winder to act as switching signals behind the closed transmission system.

The following claims set forth within the scope of the inventive idea defined by the invention, the various details of the invention may vary and differ from those set forth above by way of example only.

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Claims (6)

9 92771 A method for wirelessly transmitting an analog measurement signal from a rotating roller (10) or the like to correspondingly separate receiving devices (30), the method using a measuring sensor or a series of measuring sensors (202 to 20, 20), the signal or signal series of which is switched ) which transmit the measurement signal or signal series wirelessly to receiving devices (30) which provide an analog signal (Vout) or a corresponding signal series (Vout i ... Voutn) 10 proportional to the output message from the sensor or sensor series (20i ... 20n), and from which an analog measurement signal (Vin) or a series of signals (V ^ i ··· Vjn n) from a sensor (20) or a series of sensors (202.,. 20n) is applied to a voltage-to-frequency conversion unit (16), the frequency modulated output of which controls the optical light ) or 15 sets thereof (17i ... l7p), and the light beams (Ki ... Kp) of said transmitters (17) are received by a light detector (32), tu provided that the signal from the light detector (32) is directed to a frequency-voltage conversion unit (34) from which an output signal (Vout) or a series of signals (Vout i... .Vout n) is proportional to the measuring signal 20 of the sensors (Vin) or to a series of measuring signals (Vin 2 ... Vinn), and that the output of the voltage-frequency conversion unit (16) is connected to a series of light transmitters (172 ... 17p) which are connected in parallel. and that the light beams (Kt) of said light transmitters (17 *) are alternately controlled to sweep the view of the light-detector (32) of the receiver (30) arranged close to the light transmitters (17i). Method according to Claim 1, characterized in that the method measures the machine direction and / or transverse pressure distribution (Pm> Pt) of the nip pressure. A method for measuring the nip force and / or pressure of a nip (N) formed by a rotating roller (10) or a strip used in papermaking according to claim 2, wherein the method uses a set of measuring sensors (202 · .20n), the sensors (20) of which are placed in the rotating 35 for the width (Lq) of the paper web (W) transverse to the roll (10) or the strip, characterized in that the measurement signals from the various sensors (20) are applied to a switching unit (23) having switches (24), ,) is controlled on the basis of the rotation of the roller (10) or the like by a pulse sensor (25) or the like so that the signal of each measuring sensor (201 ... 20n) is alternately connected to the telemetry transmitter of the 5 rotating rollers (10) or the like via the switching unit (23) (26), and that in said telemetry transmitter (26), the series of measurement signals (Vln 1 ... Vin n) are transmitted wirelessly to a fixed telemetry of the pydrivating roller (10) or the like. to the receiver (30) (Figure 4). 10 A method according to claim 3, characterized in that said switching unit (23) is controlled on the basis of the rotation of the roller (10) or counter by a pulse sensor (25) so that the triggering signal of the roller (10) or counter in each rotation revolution (23) ) is controlled so that each time the pulse arrives, the switch (24 ±) that is closed is opened and the next switch (24i + 1) is closed (Fig. 4). Method according to Claim 3 or 4, characterized in that PVDF membrane sensors (20) are used as measuring sensors, the voltage level signal from which is routed via a switch unit (23) to the telemetry transmitter (26). An apparatus for transmitting a measurement signal from a rotating roller (10) or the like to separate receiving devices, wherein an analog measuring signal transmitter unit (26) is disposed in connection with the rotating roller (10) or counter, and the rotating roller (10) or counter is immediately an adapted receiving unit (30) for receiving a measurement signal wirelessly transmitted from the transmitter device (26) or a series thereof 30, the transmitter device (26) comprising a voltage-frequency conversion unit (16) having an analog measurement signal connected to its input or inputs (Vin) or a series of measurement signals (Vln x.. .Vin n), and the output of the conversion unit (16) is connected to an optical transmitter device (17J ... 17P), the receiving unit (30) comprising a light detector (32) 35 connected to the preamplifier. (33), characterized in that the output of said preamplifier (33) is connected to the input of a frequency-voltage conversion unit (34) so that said frequency-voltage the output of the conversion unit (34) gives an analog signal (Vout) tal signal series (Vout i · · · Vout n)> j ° ka is proportional to the analog measurement ignal in 5 (Vln) or signal series (Vin j. . It is n) that the light emitters are a series of light emitters (17 ^ .. 17p) connected to the shaft (14) of the rotating roller (10), that a receiving unit (30) is arranged in the vicinity of said shaft (14) so that the light beams (Kx ... Kp) of said light transmitters (17 ^ .. 17p) alternately sweep the field of view of the light detector (32) of the receiving-10 unit (30) so that the frequency modulated measurement signal (Vin) is continuously transmitted (Fig. 6) . 92771 12