Belt drive

Abstract

The present invention relates to a belt drive (2) comprising a belt (2) which is endlessly wound around a driving pulley (4a) and a driven pulley (4b). The belt drive (2) is characterized by a transmitting antenna (8) which is designed and arranged to transmit an electromagnetic wave (10) at an angle to the belt (2), where the belt (2) encloses one of the pulleys (4a; 4b), so that • a first partially reflected wave (18a) is reflected on the surface of the belt (6), • a broken wave (10b) penetrates into the material of the belt (6) and is completely reflected on the metallic surface of the pulley (4a; 4b) as a second partially reflected wave (18b), and • the second partially reflected wave (18b) strikes the boundary layer of the material of the belt (6) to the air from the inside and exits there to the outside as a third partially reflected wave (18c), a receiving antenna (16) which is designed and arranged to detect the first partially reflected wave (18a) and the third partially reflected wave (18c), and a control and evaluation unit (20) which is designed and arranged to determine a transit time difference of the first partially reflected wave (18a) and the third partially reflected wave (18c).

Description

[0001] The present invention relates to a belt drive.

[0002] Conveyor belts and other belt drives are subjected to harsh operating conditions that cause fatigue and damage.

[0003] Monitoring of belts in general, such as drive belts, printing blankets and conveyor belts using electromagnetic sensors, is therefore known.

[0004] WO 2007 / 109896 A1 discloses a sensor for monitoring the integrity of timing belts using a capacitive sensor that operates with low-frequency alternating voltage. This capacitive sensor is mounted close to the belt to detect and evaluate changes in the electrical capacitance between the sensor and the belt. The result of the capacitance measurement provides qualitative information about damaged or missing teeth on the timing belt.

[0005] US 2022 / 009721 A1 describes a network of sensors that irradiates the conveyor belt to be monitored with microwaves from both sides and measures their reflection and transmission behavior. The measurement results depend on the dielectric properties of the materials in the beam path. The evaluation of the measurement data allows conclusions to be drawn about damage to the surface of the conveyor belt and changes in its internal support structure.

[0006] A disadvantage of such measurements, however, is that substances on the surface of the conveyor belt, such as transported material or water, can interfere with the measurements. Due to its high dielectric constant (in the frequency band between 1 GHz and 100 GHz), this is particularly true for water.

[0007] One object of the present invention is to improve the possibilities for contactless monitoring of endless closed belts, including conveyor belts, of the type described above. This should be made possible, in particular, for such monitoring using microwaves. At the very least, an alternative to the known options should be provided.

[0008] The object is achieved according to the invention by a belt drive having the features according to claim 1. Advantageous further developments are described in the subclaims.

[0009] Thus, the present invention relates to a belt drive comprising a belt that is endlessly wound around a driving pulley and a driven pulley. The belt drive can be a drive comprising a belt such as a flat belt, a toothed belt, a V-belt, a V-ribbed belt, or the like. The belt drive can also be a conveyor belt, ie, a transported material or a conveyor belt.

[0010] The belt drive is characterized by a transmitting antenna which is designed and arranged to transmit an electromagnetic wave at an angle to the belt, where the belt encloses one of the pulleys, so that • a first partially reflected wave is reflected on the surface of the belt, • a broken wave penetrates the material of the belt and is fully reflected on the metallic surface of the pulley as a second partially reflected wave, and • the second partially reflected wave hits the boundary layer of the belt material to the air from the inside and exits there as a third partially reflected wave, a receiving antenna which is designed and arranged to detect the first partially reflected wave and the third partially reflected wave, and a control and evaluation unit which is designed and arranged to determine a transit time difference between the first partially reflected wave and the third partially reflected wave.

[0011] According to the invention, the metallic surface of a pulley in contact with the belt serves as a reflector for electromagnetic waves (preferably microwaves). These reflected waves are detected. The time difference between the waves allows conclusions to be drawn about the belt in order to assess its condition. In particular, damage can be detected. External influences, such as water on the surface or top of the belt, can be excluded or at least minimized sufficiently to be negligible.

[0012] The arrangement according to the invention has the following advantages: During the deflection, the belt rests on the pulley. This eliminates belt vibrations perpendicular to the direction of movement. A smaller distance is possible. Less radiation power is required than previously possible. This type of monitoring can be EMC-compliant.

[0013] No sensors are required on the underside of the belt, and the setup is simple.

[0014] Tangential radiation works at low speeds down to standstill, allowing for targeted localized examination of the belt.

[0015] The belt follows the contour of the pulley. Cracks and other damage become more apparent.

[0016] According to one aspect of the invention, the control and evaluation unit is designed and configured to control a signal generator to generate a signal with a fundamental frequency, wherein a frequency multiplier is configured and configured to generate a microwave signal as an output signal and feed it to the transmitting antenna. Very high frequencies can be generated technically more easily and cost-effectively if the frequency multiplier boosts a highly accurate fundamental frequency to the desired target frequency.

[0017] According to a further aspect of the invention, an RF amplifier is designed and configured to receive the microwave signal from the frequency multiplier, amplify it, and feed it to the transmitting antenna. With the aid of the RF amplifier, the output signal's power can be adjusted to meet requirements.

[0018] According to a further aspect of the invention, an input amplifier is designed and configured to receive the reflected electromagnetic waves from the receiving antenna, amplify them, and feed them to the control and evaluation unit. The input amplifier can increase the amplitude of the received signal to the extent required for downstream processing.

[0019] According to a further aspect of the invention, a mixer is designed and configured to receive the output signal of the transmitting antenna and the reflected electromagnetic waves of the receiving antenna, wherein the mixer is further designed and configured to multiply the signal of the reflected electromagnetic waves by the output signal of the transmitting antenna. By multiplying the received signal by the original transmitted signal, signals with the sum and difference frequencies of the two input signals can be created or generated. The latter can be so low-frequency that simple electronics are sufficient to process them.

[0020] According to a further aspect of the invention, a low-pass filter is designed and configured to low-pass filter the output signal of the mixer. The low-pass filter allows only the relevant (low-frequency) components of the mixed signal to pass through. This prevents unwanted further mixing processes at subsequent stages with nonlinear characteristics.

[0021] According to a further aspect of the invention, a low-frequency amplifier is designed and configured to amplify the output signal of the low-pass filter at low frequencies. This can represent a concrete implementation option. This allows for appropriate signal amplification.

[0022] According to a further aspect of the invention, the transmitting antenna is designed and arranged to transmit the electromagnetic wave at an angle to the belt where the belt encloses the driven pulley. This angled radiation can have two advantages.

[0023] Firstly, due to gravity at the point of radiation, a large portion of the transported material may have already fallen. Any water present, which could interfere with the measurements due to its high permittivity, has thus at least largely flowed away or been thrown outwards by centrifugal force.

[0024] Secondly, due to the angle of incidence, the electromagnetic waves can travel a longer distance in the belt and therefore experience a more significant, measurable change through the material. Furthermore, the angled incidence can amplify the effect of time-of-flight differences, because the belt's outer surface, due to its layer thickness, travels at a higher speed than its underside.

[0025] An embodiment and further advantages of the invention are explained below in conjunction with the following figures. Fig. 1 a schematic structure of a belt drive; Fig. 2 a schematic structure of a driven pulley with transmitting antenna and with receiving antenna; Fig. 3 a schematic representation of an evaluation electronics; and Fig. 4 a schematic representation of an evaluable runtime shift.

[0026] Fig. 1 shows a schematic structure of a belt drive 2, consisting of a driving pulley 4a, a belt 6 and a driven pulley 4b.

[0027] According to the invention, the metallic surface of a roller in contact with the belt 6 serves as a reflector of electromagnetic waves (preferably microwaves). Fig. 1 the driven pulley 4b is used for this purpose.

[0028] Fig. 2 shows a schematic structure of a driven pulley 4b with transmitting antenna 8 and receiving antenna 16.

[0029] The transmitting antenna 8 radiates an electromagnetic wave 10 onto the metallic surface of the pulley 4b in such a way that its main beam direction coincides with the bisector of the angle formed by the tangent 12 and its perpendicular bisector 14.

[0030] The receiving antenna 16 is aligned so that the main axis of the reflected electromagnetic wave 18 forms the same angle with the perpendicular bisector 14 as the incident wave 10 (angle of incidence = angle of reflection).

[0031] Fig. 3 shows a schematic representation of an evaluation electronics.

[0032] When monitoring the belt 6, a control and evaluation unit 20 sets the signal generator 22 to a fundamental frequency. From this signal, a frequency multiplier 24 generates a microwave signal, which is fed into the first input of a mixer 26 and an RF amplifier 28, which radiates it as an electromagnetic wave 10 via the transmitting antenna 8.

[0033] Due to the relative movement of the belt 6 with respect to the radiated electromagnetic wave 10 and the Doppler effect that occurs, the frequency of the reflected wave 18 increases or decreases according to the speed and direction of movement of the belt 6.

[0034] Fig. 4 shows a schematic representation of an evaluable runtime shift.

[0035] Fig.Figure 4 shows that, with the arrangement according to the invention, evaluable propagation time shifts occur even when the device is stationary. The incident electromagnetic wave 10 strikes the surface of the belt 6 at an angle of incidence (< 90° to the normal). Due to the higher dielectric constant of the belt 6, a first partially reflected wave 18a and a refracted wave 10b are created, which penetrates the material of the belt 6 and is fully reflected by the metallic surface of the pulley 4. This creates a second partially reflected wave 18b, which strikes the boundary layer to the air from the inside and splits there into the outward-directed third partially reflected wave 18c and another inner wave (shown in dashed lines and not labeled).

[0036] The refracted wave 10b and the second partially reflected wave 18b propagate more slowly within the belt 6 than in the air, which is why the outgoing first partially reflected wave 18a and the outgoing third partially reflected wave 18c have a propagation time difference.

[0037] The receiving antenna 16 receives the superimposed partial waves 18a, 18c, ie the outgoing first partially reflected wave 18a and the outgoing third partially reflected wave 18c, and transmits their electrical signal to the input amplifier 30. The amplified received signal is multiplied by the mixer 26 with the signal from the frequency multiplier 24.

[0038] The spectrum of the product signal contains the sum and difference frequencies of the two input signals, of which the low-pass filter 32 passes the signal components with the difference frequency and forwards them to the low-frequency amplifier 34. The downstream measuring and evaluation electronics 20 digitizes the low-frequency signal and correlates it with the signal from the position sensor 36, which provides the current speed of the belt 6 and / or the longitudinal coordinate of the point on the belt 6 toward which the receiving antenna 16 is directed. From the input data, the measuring and evaluation electronics calculates a profile of the surface of the belt 6.

[0039] For monitoring wide belts, multiple antenna pairs 8, 16 can be arranged along the width of the belt 6. Alternatively, one antenna pair 8, 16 can scan the belt 6 perpendicular to the running direction. However, the position determination must be supplemented by the corresponding coordinate. List of reference symbols (part of the description) 2 belt drive 4a driving pulley 4b driven pulley 6 belts 8 Transmitting antenna 10 electromagnetic wave 10b broken wave 12 Tangent 14 perpendicular bisectors 16 Receiving antenna 18 reflected electromagnetic waves 18a first partially reflected wave 18b second partially reflected wave 18c third partially reflected wave 20 Control and evaluation unit 22 Signal generator 24 frequency multipliers 26 mixers 28 RF amplifiers 30 input amplifiers 32 low-pass filters 34 low-frequency amplifiers QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2007 / 109896 A1

[0004] US 2022 / 009721 A1

[0005]

Claims

[1] Belt drive (2) with a belt (2) which is endlessly closed around a driving pulley (4a) and a driven pulley (4b), characterized by a transmitting antenna (8) which is designed and arranged to transmit an electromagnetic wave (10) at an angle to the belt (2), where the belt (2) encloses one of the pulleys (4a; 4b), so that • a first partially reflected wave (18a) is reflected on the surface of the belt (6), • a broken wave (10b) penetrates into the material of the belt (6) and is completely reflected on the metallic surface of the pulley (4a; 4b) as a second partially reflected wave (18b), and • the second partially reflected wave (18b) hits the boundary layer of the material of the belt (6) to the air from the inside and exits there to the outside as a third partially reflected wave (18c), a receiving antenna (16) which is designed and arranged to detect the first partially reflected wave (18a) and the third partially reflected wave (18c), and a control and evaluation unit (20) which is designed and configured to determine a transit time difference of the first partially reflected wave (18a) and the third partially reflected wave (18c). [2] Belt drive (2) according to claim 1, wherein the control and evaluation unit (20) is designed and configured to control a signal generator (22) to generate a signal with a fundamental frequency, wherein a frequency multiplier (24) is arranged and designed to generate a microwave signal as an output signal and to supply it to the transmitting antenna (8). [3] Belt drive (2) according to claim 1, wherein an RF amplifier (28) is designed and arranged to receive the microwave signal of the frequency multiplier (24), to amplify it and to feed it to the transmitting antenna (8). [4] Belt drive (2) according to one of the preceding claims, wherein an input amplifier (30) is designed and arranged to receive the reflected electromagnetic waves (18) from the receiving antenna (16), to amplify them and to feed them to the control and evaluation unit (20). [5] Belt drive (2) according to one of claims 2 to 4, wherein a mixer (26) is designed and arranged to receive the output signal of the transmitting antenna (8) and the reflected electromagnetic waves (18) of the receiving antenna (16), wherein the mixer (26) is further designed and configured to multiply the signal of the reflected electromagnetic waves (18) by the output signal of the transmitting antenna (8). [6] Belt drive (2) according to claim 5, wherein a low-pass filter (32) is designed and arranged to low-pass filter the output signal of the mixer (26). [7] Belt drive (2) according to claim 6, wherein a low-frequency amplifier (34) is designed and arranged to amplify the output signal of the low-pass filter (32) at low frequency. [8] Belt drive (2) according to one of the preceding claims, wherein the transmitting antenna (8) is designed and arranged to transmit the electromagnetic wave (10) at an angle to the belt (2) where the belt (2) encloses the driven pulley (4b).

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