Heating tape device and method for monitoring the functionality of the heating tape device

Abstract

Heating tape device (1), comprising: at least two electrically parallel, ribbon-shaped heating devices (2), each comprising a heating resistor (20) and a reference resistor (21) connected electrically in series with it, wherein the ratio of the heating resistor value to the reference resistor value is the same for all heating devices (2) at a reference temperature; and an adapter device (3) for connecting the heating devices (2) to an electrical voltage source (U) with a measuring circuit (30) which has a voltage divider circuit (31) connected electrically in parallel to the heating devices (2) and a voltage measuring device (34) which taps a measuring voltage between a center tap (P30) of the voltage divider circuit (30) and a measuring point (P20) between the heating resistor (20) and the reference resistor (21) of the respective heating device (2); where exceeding a predetermined threshold value of the measuring voltage indicates a malfunction of the heating device.

Description

[0001] The present invention relates to a heating band device, in particular for an aircraft or spacecraft, and to a method for monitoring the functionality of the heating band device.

[0002] In aircraft or spacecraft, fluid-carrying lines, especially water lines, usually need to be heated to prevent the fluid from freezing, for example when the aircraft or spacecraft is flying at high altitude or is parked for a long period of time in cold ambient temperatures.

[0003] German patent application DE 10 2010 010 929 A1 discloses a fluid line with an surrounding electrical heating device, which is designed as a so-called PTC heating device. PTC stands for "Positive Temperature Coefficient". Such heating devices have an electrically conductive heating wire whose electrical resistance increases with rising temperature, thereby reducing the power output of the heating device.

[0004] Document US 2015 / 0312963A1 describes heating modules which are configured with an optimized daisy-chain connection, which includes a power supply at the front end and waterproof heating devices and shields in the middle of the daisy chain.

[0005] Publication GB 2 478 884 A describes a heating control device which has several heating controls, each of which includes means for switching the AC power supply to the heaters on and off in order to keep one or more heaters within a desired temperature range.

[0006] The publication DE 296 12 037 U1 describes a mattress containing at least one textile surface heating element made of a fabric with electrically conductive textile fibers forming heating resistances, such as carbon fibers, with electrodes for power supply arranged along its opposite edges.

[0007] Document US 4 272 466 A describes a temperature control system for a plastic extruder with a deep well sensor and a shallow well sensor in each temperature control zone along an extruder cylinder.

[0008] Publication GB 2 378 916 A describes a heating element consisting of busbars and heating rails, which is attached to the outer surface of an inner tube.

[0009] Monitoring the functionality of such heating elements is typically achieved by measuring the overall electrical resistance of the heating element.

[0010] One of the objectives of the present invention is to provide a heating band device whose functionality can be monitored in an improved manner.

[0011] This task is solved in particular by the subject matter of the independent claims.

[0012] Advantageous designs and further developments result from the subclaims relating back to the independent claims in conjunction with the description.

[0013] According to a first aspect of the invention, a heating band device is provided. This device has at least two electrically parallel, band-shaped heating elements, each of which has a heating resistor and a reference resistor connected electrically in series with it, wherein the ratio of the heating resistor value to the reference resistor value is the same for all heating elements at a reference temperature. Furthermore, the heating band device has an adapter for connecting the heating elements to an electrical voltage source with a measuring circuit. This circuit includes a voltage divider circuit connected electrically in parallel with the heating elements and a voltage measuring device that taps a measuring voltage between a center tap of the voltage divider circuit and a measuring point between the heating resistor and the reference resistor of the respective heating element.Exceeding a predetermined threshold of the measuring voltage indicates a malfunction of the heating device. In the following, the term "heating band" is used synonymously with "heating band device".

[0014] According to the invention, the heating tape is formed in particular by several heating elements connected in parallel. The heating elements each comprise, in particular, a heating element and a reference resistor, wherein the heating element and the reference resistor are connected in series. Thus, the heating element and the reference resistor form a voltage divider. The heating tape therefore has several heating elements configured as voltage dividers. These voltage dividers all have, in particular, the same division ratio, meaning that the ratio of the resistance of the heating element to the resistance of the reference resistor is the same for all heating elements at a reference temperature, apart from manufacturing tolerances of the resistor elements. The reference temperature can, for example, be a temperature between 0 degrees Celsius and 30 degrees Celsius.The heating elements can be connected to an electrical voltage source by means of an adapter or connection device. According to the invention, the adapter device includes a measuring circuit with a voltage divider circuit. This is connected in parallel to the heating elements. A measuring voltage is determined by taking a voltage tap between the center tap of the voltage divider circuit of the measuring circuit and a center tap of the voltage dividers of the heating elements. Since the voltage dividers of the heating elements all have the same division ratio, the measuring voltage is independent of the number of heating elements. If the functionality of one of the heating elements is impaired, for example because the heating element or the reference resistor is defective, or if the total resistance of the individual heating element changes in general, this leads to a change, in particular an increase, in the measuring voltage.If the measured voltage exceeds a predetermined threshold, this indicates a malfunction of the heating device.

[0015] Since the measuring voltage is independent of the number of heating elements due to the identical division ratio for all heating elements, the number of heating elements per heating tape is freely selectable without requiring any adjustment of the adapter. Thus, according to the invention, a heating tape is provided which has a modular design with respect to the number of heating elements and whose functionality can be monitored in a simple and reliable manner. A particular advantage lies in the matching of the resistance ratios between the heating element's resistance and the reference resistance, as this allows monitoring of the heating tape independently of the total resistance of the heating elements, and therefore the same identically configured measuring circuit can always be used to monitor functionality.

[0016] In a preferred embodiment of the heating band, the voltage divider circuit comprises a first measuring resistor, a second measuring resistor connected in series with it, and the ratio of the first measuring resistor value to the second measuring resistor value is equal to the ratio of the heating resistor value to the reference resistance value of the heating elements. In particular, the voltage divider circuit has the same division ratio as the heating elements. This advantageously achieves a large change in the measuring voltage. This is especially beneficial with regard to measurement accuracy, since the large change in the measuring voltage allows a failure of a heating element to be reliably distinguished from other resistance changes in the heating elements, for example, due to temperature changes.

[0017] It is particularly preferred that each heating element additionally has a control device electrically connected in series with the heating element, by means of which an electrical connection to the heating element can be established to set an operating state of the heating element and interrupted to set a standby state of the heating element. Such functional coupling of each heating element to its own control device allows each heating element to be controlled independently. In particular, different heating characteristics can be provided for different sections of the heating element. This advantageously reduces the energy consumption of the heating element.

[0018] It can be particularly advantageous to provide that the control unit switches the heating element to operating mode when a first reference temperature of the heating element is undershot, and switches the heating element to standby mode when a second reference temperature of the heating element is reached. This allows each heating element to have its own switch-on and switch-off temperatures. The temperature can be measured, for example, by means of a temperature sensor and transmitted to the control unit as an input signal. In particular, the control unit itself can also incorporate the temperature sensor.

[0019] Preferably, the first and second reference temperatures are the same. This offers the advantage of particularly simple control by the control device. However, it is also conceivable that the first and second reference temperatures are chosen differently. For example, the first reference temperature can be lower than the second reference temperature. This can advantageously reduce the number of switching operations of the control device.

[0020] According to an advantageous embodiment, the measuring circuit additionally includes a first switching device which, in a first switching state, bridges the reference resistors of the heating elements. The adjustability of this bridge or bypass around the reference resistors offers the advantage of allowing a heating operating state of the heating band to be set in which no evaluation of the measuring voltage takes place and, in particular, in which the reference resistors are not subjected to a voltage. This reduces the energy consumption of the heating band and simultaneously extends the service life of the reference resistors.

[0021] Advantageously, the measuring points of the heating devices are electrically connected to a first common line, and the reference resistors of the heating devices are electrically connected to a first signal line. The first switching device electrically connects a second end tap of the voltage divider circuit to the first common line in the first switching state and to the first signal line in the second switching state. This advantageous design provides a simple way to bridge the reference resistors with the first switching device.

[0022] According to a further embodiment, the measuring circuit also has a second switching device which, in an open state, interrupts the electrical connection formed by the voltage measuring device between the center tap of the voltage divider circuit and the measuring point.

[0023] According to a further advantageous embodiment, the adapter device additionally features a polarity reversal circuit, by means of which the polarity of a DC voltage applied to the heating elements can be reversed. In a DC heating operating state of the heating element, the conventional current direction is from the control device to the heating resistor, and in a DC test state of the heating element, the direction is reversed. The polarity reversal circuit advantageously allows the direction of current flow through the heating elements to be changed. Thus, when operating the heating element with DC, the current flow direction can be reversed to check its functionality. This is particularly advantageous when control devices are provided on the heating elements. By reversing the current flow direction, it can be easily ensured that all heating elements are switched to the operating state.For example, the control devices can be configured so that if the direction of current flow is reversed, the heating devices are automatically switched to operating current.

[0024] Particularly advantageous is the inclusion of a diode in each heating element, electrically connected in parallel to the control element such that, during DC heating operation of the heating element, a voltage is applied across the diode in reverse bias, and during DC test operation, in forward bias. In the test state, the diode thus acts as a bypass diode. This ensures that all heating elements can be switched to operating mode regardless of the switching state of the control elements. Consequently, the functionality of the heating element can be checked in a particularly simple manner, independent of both the switching state of the control elements and the number of heating elements per heating element.

[0025] Alternatively, each heating element can be provided with a diode arranged in a bridge between a bridge point between the control device and the heating resistor and a second signal line. The measuring circuit additionally includes a third switching device which, in a first switching state for setting the operating state of the heating elements, electrically connects a first end tap of the voltage divider circuit to a second bus line to which the control devices are electrically connected. In a second switching state for setting the DC test state of the heating element, it electrically connects the first end tap of the voltage divider circuit to the second signal line, with a forward voltage applied to the diode in the DC test state. Thus, an additional second signal line is provided.The heating elements are electrically connected to a second busbar via their control unit and, through a diode, to an additional second signal line via a bridge point located between the control unit and the heating element. The third switching device allows alternating switching of the first end tap of the voltage divider circuit to either the second signal line or the second busbar. This advantageously provides a way to completely decouple the control units from the current flow by setting the second switching state of the third switching device during the DC test state of the heating element. This offers the advantage of preventing "backward currenting" of the control units, thus eliminating the risk of damage to the control units due to a reversal of the current flow direction.

[0026] According to an alternative embodiment, the heating band has a third signal line instead of the second signal line. Each control unit connects a control input to this third signal line, and the control units switch the heating devices into the operating state when a predetermined signal voltage is applied to the control input. Instead of the third switching device, the measuring circuit also has a fourth switching device, which, when closed, connects a first control line of the measuring circuit (connectable to or already connected to a voltage source) to the third signal line. Accordingly, an additional third signal line is provided, which can be electrically connected to a signal line of the measuring circuit by means of a fourth switching device. A signal voltage can be applied to a signal input of the control units via this signal line.As a result of the signal voltage being applied, the control devices activate the heating elements. This provides a particularly advantageous way to perform a functional test of the heating tape without reversing the polarity, since applying the signal voltage to the control inputs of the control devices puts all heating elements of the tape into operation. Furthermore, this configuration of the heating tape also advantageously allows for AC operation.

[0027] The heating element of the heating device can be designed, in particular, as a meandering heating conductor track formed on the surface of a support layer. Due to the meandering path of the heating conductor track, individual sections of the track run parallel to each other. This offers the advantage of providing an extremely space-saving design with a relatively large heating surface.

[0028] The heating conductors can be formed on the substrate, particularly by means of a printing or etching process. This advantageously enables efficient and cost-effective production of the heating tape. The substrate is preferably designed as a continuous tape on which the heating elements are arranged.

[0029] In a further advantageous development of the heating tape, at least one bridge is provided between two adjacent sections of the heating conductor to adjust the heating resistance value. This bridge shortens the path from an input connection point to an output connection point. By adjusting the position of the bridge, the resistance, which is known to depend on the length of the conductor, can be set.

[0030] In particular, it can be provided that the heating element is supplied as a semi-finished product with a predetermined number of bridges, and that a portion of these bridges is subsequently removed according to the size of the reference resistor assigned to the respective heating element. Of course, it is also possible to add the bridges subsequently.

[0031] The reference resistors are advantageously designed as power resistors. However, they can also be designed as conductive traces. If the heating tape has a carrier layer or a carrier strip, the reference resistors and the heating resistors are preferably arranged on opposite surfaces of the carrier strip. This ensures a compact design of the heating tape.

[0032] An advantageous use of the heating tape according to the invention lies particularly in the heating of pipe or conduit systems, especially fluid lines, such as water pipes. The heating tape according to the invention can be used particularly in the automotive sector, preferably in aircraft or spacecraft, for heating fluid lines, such as water, oil, kerosene lines, or the like.

[0033] According to a further aspect of the invention, a method for monitoring the functionality of the heating band according to one of the preceding embodiments is provided. The method comprises the following steps: - Applying voltage to the heating devices; - Comparing the measured voltage taken from the voltage measuring device with a threshold value; and - Providing an error signal if the fault voltage exceeds the threshold.

[0034] According to the invention, the test state of the heating device is first set, i.e., a voltage is applied to all heating elements, in particular to all heating resistors and all reference resistors. In the basic form of the heating band, this corresponds to simply switching on the voltage source. If the heating elements have control devices, the test state can be set in various ways. If a diode is provided to bypass or circumvent the control devices, the polarity of the voltage applied to the heating elements is reversed such that it is applied to the diode in the forward direction. If a control input is provided on the control devices, the control voltage is applied to this input, so that the control device switches the heating elements to the operating state.

[0035] The measured voltage is then compared to a threshold value. Since a voltage is applied across all heating and reference resistors, the measured voltage, due to its dependence on the resistance ratio of the heating resistors to the reference resistors, indicates that at least one of the heating elements has increased resistance when a threshold value is exceeded. The measured voltage is compared to the threshold value. If the measured voltage is greater than or equal to the threshold value, an error signal is generated. This can be a data signal, which is transmitted via a transceiver unit and / or the connecting lines of the adapter devices to a central control unit or similar device. Alternatively, the measured voltage value can be transmitted via the transceiver unit and / or the connecting lines of the adapter devices to the central control unit, where the error signal is generated.

[0036] One method for operating the heating tape involves operating it in heating mode. If control devices are provided, individual heating elements may be in standby mode while the remaining heating elements are in operating mode. The method for operating the heating tape also includes carrying out the previously described procedure for monitoring the functionality of the heating tape. Accordingly, the heating tape is switched to test mode, and the aforementioned steps are performed. Subsequently, the heating mode is restored.

[0037] Preferably, the monitoring procedure is performed several times within a specific period. Advantageously, the occurrence of an error signal is stored, for example, in a memory provided in the adapter device or the central control unit. The single occurrence of an error signal, indicating a malfunction of at least one heating element, specifically indicates a fault condition of the heating band. By repeating the monitoring procedure several times, it can be determined whether the error signal occurs again. If this is not the case, a fault condition of the heating band is still indicated. Thus, the event that the heating element and reference resistor of one of the heating elements fail successively, and consequently the threshold value of the measuring voltage is no longer exceeded, is still considered a fault condition.

[0038] With regard to directions and axes, in particular directions and axes relating to the course of physical structures, the course of an axis, direction or structure “along” another axis, direction or structure is understood to mean that these, in particular the tangents resulting at a respective point of the structures, each run at an angle of less than or equal to 45 degrees, preferably less than or equal to 30 degrees and in particular preferably parallel to each other.

[0039] The invention will now be explained with reference to the figures in the drawings. The figures show: Fig. 1 a schematic representation of a heating band according to an embodiment of the present invention; Fig. 2 a schematic representation of an electrical circuit of the heating band according to an embodiment of the present invention in a heating operating state; Fig. 3 a schematic representation of the electrical circuit of the Fig. 2 in a test state; Fig. 4 a schematic representation of an electrical circuit of the heating band according to a further embodiment of the present invention in a heating operating state; Fig. 5 a schematic representation of the electrical circuit of the Fig. 4 in a test state; Fig. 6 a schematic representation of an electrical circuit of the heating band according to a preferred embodiment of the present invention in a heating operating state; Fig. 7 a schematic representation of the electrical circuit of the Fig. 6 in a test state; and Fig. 8 a schematic representation of a preferred embodiment of a heating device of the heating band according to an embodiment of the present invention.

[0040] In the figures, the same reference symbols denote identical or functionally equivalent components, unless otherwise stated.

[0041] Fig. Figure 1 schematically shows a heating band 1 with at least two heating elements 2, each comprising a heating resistor 20 and an optional control unit 22, and an adapter unit 3. The heating elements 2 each additionally include a reference resistor 21, which is Fig. 1 is not shown.

[0042] As in Fig. As shown in Figure 1, the heating devices 2 are arranged in a band-like pattern. In particular, several heating devices 2 are arranged consecutively in a longitudinal direction L1. ... Fig. As shown by way of example in Figure 1, in particular a carrier strip or carrier layer 10 can be provided, on whose surface 10a the heating devices 2 are arranged.

[0043] Fig. Figure 1 further shows that the adapter device 3 preferably forms a first end 1A of the heating tape 1. In particular, the adapter device 3 is advantageously arranged at a first end section 10A of the carrier layer 10. The adapter device 3 serves to connect the heating devices 2 to an electrical voltage source U. Accordingly, the adapter device 3 has corresponding electrical connections 3A, 3B, as shown in Figure 1. Fig. 1 is shown schematically. Furthermore, the adapter device 3 can advantageously also have signal transmission connections 3C, 3D for receiving or transmitting signals, as also shown in Fig. Figure 1 shows that, alternatively or additionally, the adapter device 3 may have a transmitter / receiver unit 60 for receiving or transmitting signals, as shown schematically, for example, in Figure 1. Fig. 2 is shown.

[0044] As also in Fig. As shown in Figure 1, the heating tape 1 can optionally have an insulating cap 15, which forms a second end 1B of the heating tape 1 located opposite to the first end 1A with respect to the longitudinal direction L1. The insulating cap 15 is advantageously arranged, in particular, on a second end section 10B of the carrier layer 10. The insulating cap 15 serves to electrically insulate the electrical components of the heating tape 1.

[0045] The Fig. Figures 2 to 7 schematically illustrate the electrical-functional structure of the heating tape 1. Accordingly, the heating elements 2 of the heating tape 1 are electrically connected in parallel. In particular, each heating element 2 comprises a heating resistor 20 and a reference resistor 21, with the reference resistor 21 and the heating resistor 20 being electrically connected in series within the heating element 2. The ratio of the resistance value of the heating resistor 20 to the resistance value of the reference resistor 21 is the same for all heating elements 2 at a reference temperature. The reference temperature can be adapted to the specific application of the heating tape 1. For example, in an aviation application, the reference temperature can be set to 5 degrees Celsius.

[0046] As in the Fig. As shown in Figures 2 to 7, the heating resistors 20 are preferably connected to a first busbar 5 via a first connection point A5 located between the heating resistor 20 and the reference resistor 21, and to a second busbar 6 via a second connection point A5. The reference resistors 21 of the heating devices 2 are further connected to a first signal line 7.

[0047] As in the Fig. As shown in Figures 2 to 7, each of the heating devices 2 optionally includes the control device 22. This is electrically connected in series with the heating resistor 20. In particular, the control device 22 can be connected between the second connection point A6 and the heating resistor 2. An electrical connection to the heating resistor 21 can be established or interrupted by means of the control device 22. Specifically, the control device 22 forms an on / off switch which, in the closed state, contacts the respective heating resistor 20 with the second busbar 6, allowing an electric current to flow through the heating resistor 20, and, in the open state, interrupts the electrical connection between the heating resistor 20 and the second busbar 6. A state in which the control device 22 establishes the electrical connection corresponds to an operating state of the heating device 2.A state in which the control device 22 interrupts the electrical connection corresponds to a rest state of the heating device 2.

[0048] The control device 22 can, in particular, have functions for detecting and comparing a temperature. Specifically, it can be provided that the control device 22 switches the heating device 2 to the operating state when a first reference temperature of the heating resistor 20 is undershot, and switches the heating device 2 to the standby state when a second reference temperature of the heating resistor 20 is reached. Preferably, the first and second reference temperatures are the same. However, it can also be provided that the first reference temperature is lower than the second reference temperature, or vice versa. For example, the first reference temperature can be 0.5 degrees Celsius and the second reference temperature 8 degrees Celsius.

[0049] As in the Fig. As shown in Figures 2 to 7, the adapter device 3 includes a measuring circuit 30. The measuring circuit 30 includes a voltage divider circuit 31 and a voltage measuring device 34.

[0050] The voltage divider circuit 30 comprises, in particular, a first measuring resistor 32 and a second measuring resistor 33 connected electrically in series with it. The voltage divider circuit 31 is connected electrically in parallel with the heating devices 2. This can be done, in particular, as shown in the Fig. Figures 2 to 7 show that this is achieved by electrically contacting a first end tap 31A of the voltage divider circuit 31 to the second busbar 6 and electrically contacting a second end tap 31B of the voltage divider circuit 31 to the first signal line 7.

[0051] The voltage measuring device 34 taps a measuring voltage between a center tap P30 of the voltage divider circuit 30 and a measuring point P20 between the heating resistor 20 and the reference resistor 21 of the respective heating device 2. The center tap P30 is located between the first and the second measuring resistors 32, 33. The measuring point P20 functionally corresponds to the first connection point A5 of the heating resistors 20 to the first busbar 5. Advantageously, the voltage measuring device 34 is electrically connected to the first busbar 5. The voltage measuring device 34 can, in particular, be implemented using an operational amplifier.

[0052] In a fault-free operating state, in which all heating elements 2 of the heating band 1 are operating simultaneously, the voltage measuring device 34 measures a measuring voltage. Since the ratio of the heating resistance value to the reference resistance value is the same for all heating elements 2, a change in the measuring voltage indicates a change in the resistance of one of the heating elements 2. In particular, exceeding a predetermined threshold value of the measuring voltage indicates a malfunction of the heating element 2. If the measuring voltage exceeds the threshold value, an error signal can be generated. The error signal can, for example, be generated by the transmitter / receiver unit 60 based on the measuring voltage. For this purpose, the transmitter / receiver unit 60 may have a processor and memory. It is also conceivable that the transmitter / receiver unit 60 simply transmits a value equivalent to the measuring voltage.The transmission to another functional unit can be done wirelessly and / or via the signal connections 3C, 3D, for example.

[0053] Particularly advantageous is the ratio of the resistance value of the first measuring resistor 32 to the resistance value of the second measuring resistor 33 being chosen to be equal to the ratio of the heating resistance value to the reference resistance value of the heating elements 2. This offers the advantage that the measuring voltage in the fault-free operating state, in which all heating elements 2 of the heating band 1 are in operation simultaneously, is zero in an ideal circuit, and is approximately zero in reality.

[0054] As in the Fig. As shown in Figures 2 to 7, the measuring circuit 30 preferably also includes a first switching device 35, which in a first switching state bridges the reference resistors 21 of the heating devices 2. This offers the advantage that a pure heating operating state of the heating band 1 can be set, in which the heating resistors 20 can be supplied with an operating voltage, but no measuring voltage is detected or evaluated. In particular, this prevents a voltage drop across the reference resistors, thereby reducing energy consumption.

[0055] As in the Fig. 2, Fig. 4 and Fig. As shown in Figure 6, the first switching device 35, in a first switching state, establishes an electrical connection between the second end tap 31B of the voltage divider circuit 31 and the first busbar 5. Fig. 3, Fig. 5 and Fig. Figures 7 each show a second switching state of the first switching device 35. In the second switching state, the first switching device 35 establishes an electrical connection between the second end tap 31B of the voltage divider circuit 31 and the first signal line 7 in a first switching state.

[0056] As the Fig. Figures 2 to 7 further show that the measuring circuit 30 may in particular have a second switching device 36. In an open state, the second switching device 36 interrupts the electrical connection formed by the voltage measuring device 34 between the center tap P30 of the voltage divider circuit 31 and the measuring point P20. Fig. 2, Fig. 4 and Fig. Figure 6 shows the second switching device 36 in the open state. Fig. 3, Fig. 5 and Fig. Figure 7 shows the second switching device 36 in a closed state, in which it electrically connects the center tap P30 to the measuring point P20, in particular to the first busbar 5.

[0057] Providing a control device 22 on each of the heating devices 2 offers the advantage that the operation of each heating device 2 can be controlled individually. However, an operating state can occur in which only some of the heating devices 2 are in operation.

[0058] The Fig. 2 and Fig. Figure 3 shows a first advantageous design of the heating band 1, which is particularly suitable for operation with a direct current voltage. Fig. 4 and Fig. Figure 5 shows a second advantageous design of the heating band 1, which is also particularly suitable for operation with a DC voltage. Fig. 6 and Fig. Figure 7 shows a third advantageous design of the heating band 1, which is particularly suitable for operation with an alternating voltage.

[0059] According to the in the Fig. In the designs shown in Figures 2 to 4, the adapter device 3 additionally features a polarity reversal circuit 50. This is shown in the Fig. Figures 2 to 4 are shown schematically with a first pole-changing switch 51 and a second pole-changing switch 52. In a diagram in the Fig. 2 and Fig. In the DC heating operating state of the heating band 1 shown in Figure 4, the first pole-changing switch 51 establishes an electrical connection between the electrical terminal 3B, intended for connection to a negative terminal of the voltage source U, and the second end tap 31B of the voltage divider circuit 31. The second pole-changing switch 52 establishes an electrical connection between the electrical terminal 3A, intended for connection to a positive terminal of the voltage source U, and the first end tap 31A of the voltage divider circuit 31. In the DC heating operating state of the heating band 1, an electric current flows, in accordance with the conventional current direction from the positive to the negative terminal, from the first end tap 31A of the voltage divider circuit 31 through the control device 22 and – if this device sets an operating state of the respective heating element 2 – through the heating resistor 20.

[0060] As in the Fig. 3 and Fig. As shown in Figure 6, the polarity of the voltage U applied to the heating elements 2 can be reversed using the polarity reversing circuit 50. For this purpose, the polarity switches 51 and 52 are inserted into the positions shown in the Fig. 3 and Fig. The switching state shown in Figure 5 is brought into operation. The first pole-changing switch 51 establishes an electrical connection between the electrical terminal 3B, intended for connection to a negative terminal of the voltage source U, and the first end tap 31A of the voltage divider circuit 31. The second pole-changing switch 52 continues to establish an electrical connection between the electrical terminal 3A, intended for connection to a positive terminal of the voltage source U, and the second end tap 31B of the voltage divider circuit 31.

[0061] Reversing the polarity allows the setting of a DC test state of the heating band 1, in which the direction of current flow through the heating device 2 is reversed to the direction of current flow in the DC heating operating state.

[0062] The Fig. 2 and Fig. Figure 4 shows a preferred embodiment of the measuring circuit 30, which includes the first switching device 35. In the heating operating state, this device is preferably in its first switching state, as shown in the Fig. 2 and Fig. 4 is shown. As in the Fig. 2 and Fig. As also shown in Figure 4, the second switching device 36 is preferably in the open position during the heating operation state of the heating band 1.

[0063] As in the Fig. 2 and Fig. As shown in Figure 3, it can be advantageously provided that each heating device 2 has a diode 23 connected in parallel to the control device 22. As shown in Figure 3, each heating device 2 has a diode 23 connected in parallel to the control device 22. Fig. As shown in Figure 2, the diode blocks current in the DC heating operating state of the heating band. In the DC test state, in which the polarity is reversed, the diode 23 is connected in the forward direction and forms a bypass to the control device 22.

[0064] Based on the one in Fig. The functionality of the heating band 1 can be checked by the following procedure, based on the switching state of the measuring circuit 30 shown in Figure 3. A voltage is applied to the heating elements 2, for example by switching on the DC power source U or by reversing the corresponding direction shown in Figure 3. Fig. Polarity shown in 2 with the DC power source switched on can be adjusted by setting the in Fig. The switching state of the polarity reversal circuit 50 is shown in Figure 3. Furthermore, the measured voltage tapped by the voltage measuring device 34 is compared with a threshold value. If the fault voltage exceeds the threshold value, a fault signal is provided. The fault signal can be provided, in particular, in the manner described above.

[0065] The in Fig. 4. The heating band 1 shown in the DC heating operating state differs from the one shown in the Fig. 2 and Fig. The heating band 1 shown in Figure 3 is connected via the diode 23. The heating band 1 has an additional second signal line 8. Furthermore, the measuring circuit 37 has an additional third switching device 37.

[0066] As in Fig. As shown in Figure 4, the diode is arranged in a bridge between a bridge point P21 between the control device 22 and the heating resistor 20 and the second signal line 8. The third switching device 37 is in Fig. Figure 4 shows a first switching state for setting the operating state of the heating devices 2. In the first switching state, the third switching device 37 electrically connects the first end tap 31A of the voltage divider circuit 31 to the second busbar 6. In a Fig. In the second switching state shown in Figure 5 for setting the DC test state of the heating band 1, the third switching device 37 electrically connects the first end tap 31A of the voltage divider circuit 31 to the second signal line 8.

[0067] In the Fig. In the DC heating operating state shown in Figure 4, an electric current flows according to the conventional current direction from the positive to the negative terminal, therefore from the first end tap 31A of the voltage divider circuit 31 through the control device 22 and – if this sets an operating state of the respective heating device 2 – through the heating resistor 20. Since in Fig. 4 when the first switching device 35 is switched to its first switching state, the reference resistors 21 of the heating devices 2 are bridged.

[0068] In the Fig. In the DC test state shown in Figure 5, the polarity of the voltage applied to the end taps 31A and 31B of the voltage divider circuit 30 is reversed by means of the polarity reversal circuit 50. The first switching device 35 is in its second switching state, the second switching device 36 is in its closed state, and the third switching device is in its second switching state. As shown in Figure 5, a current is applied to the diode 23. Fig. Figure 5 shows that in the DC test condition, a voltage is applied in the forward direction. The heating resistors 20 and the reference resistors 21 of the heating devices 2 are thus subjected to a voltage independently of the switching state of the control devices 22.

[0069] Based on the one in Fig. The functionality of the heating band 1 can be checked using the following procedure, based on the switching state of the measuring circuit 30 shown in Figure 5. A voltage is applied to the heating elements 2, for example by switching on the DC power source U at the point shown in Figure 5. Fig. 5 shown switching state or by reversing accordingly in Fig. Polarity shown in 4 with DC power source U switched on can be achieved by adjusting the Fig. The switching state of the polarity reversal circuit 50 is shown in Figure 5. Furthermore, the measured voltage tapped by the voltage measuring device 34 is compared with a threshold value. If the fault voltage exceeds the threshold value, a fault signal is provided. The fault signal can be provided, in particular, in the manner described above.

[0070] The in the Fig. 6 and Fig. The heating band 1 shown in section 7 advantageously enables a check of the functionality of the heating devices 2 when the adapter device 3 is connected to an AC voltage source U.

[0071] Instead of the ones in the Fig. 4 and Fig. The second signal line 8 shown in section 5 indicates that it is located in the Fig. 6 and Fig. The heating band 1 shown in Figure 7 has a third signal line 9. Furthermore, the measuring circuit 30 has a fourth switching device 38 and an additional first control line 9 instead of the third switching device 37. The Fig. The diode 23 shown in sections 2 to 5, as well as the polarity reversal circuit 50, is located in the diagram shown in the diagram. Fig. 6 and Fig. Heating band 1 shown in section 7 is not present.

[0072] Each control unit 22 has a control input 24 electrically connected to the third signal line 9. The control units 22 have a function which, when a predetermined signal voltage is present at the control input 24, switches the heating devices 2 into the operating state.

[0073] The first control line 39 of the measuring circuit 30 is preferably connectable to a voltage source. For example, this can be done, as in Fig. 6 and Fig. As shown in Figure 7, the connection is made via terminals 3A and 3B of the adapter device 3. Alternatively, it is also conceivable to provide a local voltage source within the adapter device 3, to which the first control line 39 is connected.

[0074] The fourth switching device 38 is in Fig. 6 shown in an open state. In which in Fig. In the closed state shown in Figure 7, the fourth switching device 38 connects the first control line 39 of the measuring circuit 30 to the third signal line 9. This causes a voltage to be applied to the control inputs 24 of the control devices 22, which thereby set an operating state of the heating devices 2.

[0075] The measuring circuit 30 can still be used in the Fig. 6 and Fig. Figure 7 schematically depicts a signal control unit 40, which is connected between the voltage source U and the third signal line 9. The signal control unit 40 can, in particular, include a rectifier. This offers the advantage that a DC voltage can be applied to the control inputs 24.

[0076] Fig. Figure 6 shows the heating band 1 in an AC heating operating state. The individual heating elements 2 are supplied with an AC voltage. Whether all heating resistors 20 are actually energized, i.e., in their operating state, depends on the switching state of the respective control device 22. Preferably, the first switching device 35 bridges the reference resistors 21, as shown in Fig. 6 shown. Furthermore, in the AC heating operating state, it is preferred if the second switching device 36 is switched in the open state.

[0077] Fig. Figure 7 shows the heating element 1 in an AC test state. Here, the first switching device 35 is in its second switching state, the second switching device 36 is in its closed state, and the fourth switching device 38 is also in its closed state. Therefore, the signal voltage is present at the control inputs 24 of all control devices 22, causing the control devices 22 to switch the heating elements 2 into the operating state. Accordingly, a voltage can be measured using the voltage measuring device 34, indicating whether the heating elements 2 are in a functional state.

[0078] Based on the one in Fig. The functionality of the heating band 1 can be checked using the following procedure, based on the switching state of the measuring circuit 30 shown in Figure 7. A voltage is applied to the heating elements 2, for example by switching on the AC voltage source U at the point shown in Figure 7. Fig. The switching state shown in Figure 7 or by closing the fourth switching device 38 and, if necessary, switching the switching devices 35 and 36 with the voltage source U switched on. Furthermore, the measuring voltage tapped off by the voltage measuring device 34 is compared with a threshold value. If the fault voltage exceeds the threshold value, a fault signal is provided. The fault signal can be provided, in particular, in the manner described above.

[0079] Fig. Figure 8 shows an example of a detailed view of a possible design of the heating resistor 20 of the heating devices 2. Accordingly, the heating resistor 20 is designed as a heating conductor track 12 formed on a surface 10a of a carrier layer 10. The heating conductor track 12 runs in a meandering pattern. In particular, individual sections 11 of the heating conductor track run parallel to each other or alongside each other. This advantageously results in a space-saving design. Furthermore, the heating resistor 20 can be manufactured very easily in this way, for example by a printing or etching process.

[0080] As in Fig. As further shown in Figure 8, at least one bridge 13, 14 is formed between two adjacent sections 11 to adjust the ratio of the heating resistance value to the reference resistance value. The bridges 13, 14 connect two adjacent sections 11. Depending on the positioning of the bridges, the effective length of the individual sections 13 is shortened, which leads to a reduction in the resistance value of the heating conductor track 12.

[0081] As in Fig.As shown in Figure 8, several first bridges 13 and second bridges 14 are preferably provided. The first bridges 13 are arranged at a first distance from each other and connect two adjacent sections 11. The second bridges 14 are arranged at a second distance from each other and connect two further sections 11. The second distance is smaller than the first. By removing a certain number of the first bridges 13, a coarse adjustment of the resistance value can be made. Fine adjustment is then achieved by further removing a certain number of the second bridges 14. This method increases the resistance value of the heating conductor track. Of course, bridges 13, 14 can also be added subsequently to reduce the resistance value.

[0082] Although the present invention has been explained above by way of example embodiments, it is not limited to these, but can be modified in many ways. In particular, combinations of the preceding embodiments are also conceivable. REFERENCE MARK LIST 1 heating tape 1A First end of the heating tape 1B second end of the heating tape 2 heating devices 3 Adapter setup 3A, 3B electrical connections 3C, 3D signal transmission connectors 5 first collection line 6 second collection line 7 first signal line 8 second signal line 9 third signal line 10 carrier layer 10A first end section of the carrier layer 10B second end section of the carrier layer 11 Heating conductor track 12 sections of the heating conductor track 13 first bridges 14 second bridges 15 Insulation cap 20 heating resistors 21 Reference resistor 22 Control unit 23 Diode 30 measuring circuit 31 Voltage divider circuit 31A first end tap of the voltage divider circuit 31B second end tap of the voltage divider circuit 32 first measuring resistor 33 second measuring resistor 34 Voltage measuring device 35 first switching device 36 second switching device 37 third switching device 38 fourth switching device 39 first control line of the measuring circuit 50 pole reversal circuit 51 first pole changer 52 second pole changer 60 Transmit / Receive Unit A5 first junction A6 second junction P20 measuring point P21 Bridge Point P30 Center tap of the voltage divider circuit U voltage source L1 Longitudinal direction

Claims

[1] Heating tape device (1) comprising: at least two electrically parallel, ribbon-shaped heating devices (2), each comprising a heating resistor (20) and a reference resistor (21) connected electrically in series with it, wherein the ratio of the heating resistor value to the reference resistor value is the same for all heating devices (2) at a reference temperature; and an adapter device (3) for connecting the heating devices (2) to an electrical voltage source (U) with a measuring circuit (30) which has a voltage divider circuit (31) connected electrically in parallel to the heating devices (2) and a voltage measuring device (34) which taps a measuring voltage between a center tap (P30) of the voltage divider circuit (30) and a measuring point (P20) between the heating resistor (20) and the reference resistor (21) of the respective heating device (2); where exceeding a predetermined threshold value of the measuring voltage indicates a malfunction of the heating device. [2] Heating band device (1) according to claim 1, wherein the voltage divider circuit (31) has a first measuring resistor (32), a second measuring resistor (33) connected in series with it, and the ratio of the first measuring resistor value (32) to the second measuring resistor value (33) is equal to the ratio of the heating resistor value to the reference resistor value of the heating devices (2). [3] Heating band device (1) according to claim 1 or 2, wherein each of the heating devices (2) additionally has a control device (22) electrically connected in series with the heating resistor (20), by means of which an electrical connection to the heating resistor (21) can be established to set an operating state of the heating device (2) and can be interrupted to set a standby state of the heating device (2). [4] Heating band device (1) according to claim 3, wherein the control device (22) switches the heating device (2) to the operating state when a first reference temperature of the heating resistor (20) is undershot and switches the heating device (2) to the standby state when a second reference temperature of the heating resistor (20) is reached, wherein the first and the second reference temperature are preferably the same. [5] Heating band device (1) according to one of the preceding claims, wherein the measuring circuit (30) additionally has a first switching device (35) which in a first switching state forms a bridging of the reference resistors (21) of the heating devices (2). [6] Heating band device (1) according to claim 5, wherein the measuring points (P20) of the heating devices (2) are electrically connected to a first common line (5) and the reference resistors (21) of the heating devices (21) are electrically connected to a first signal line (7), wherein the first switching device (35) electrically connects a second end tap (31B) of the voltage divider circuit (31) to the first common line (5) in the first switching state and to the first signal line (7) in a second switching state. [7] Heating band device (1) according to one of the preceding claims, wherein the measuring circuit (30) additionally has a second switching device (36) which, in an open state, interrupts the electrical connection formed by the voltage measuring device (34) between the center tap (P30) of the voltage divider circuit (31) and the measuring point (P20). [8] Heating band device (1) according to one of claims 3 to 7, wherein the adapter device (3) additionally has a polarity reversal circuit (50) by means of which the polarity of a DC voltage that can be applied to the heating devices (2) can be reversed, wherein in a DC heating operating state of the heating band device (1) the technical current direction is directed from the control device (22) to the heating resistor (20) and in a DC test state of the heating band device (1) in the opposite direction. [9] Heating band device (1) according to claim 8, wherein each heating device (2) has a diode (23) which is electrically connected in parallel to the control device (22) such that in the DC heating operating state of the heating band device (1) a voltage is applied to the diode (23) in reverse direction and in the DC test state in forward direction. [10] Heating band device (1) according to claim 8, wherein each heating device (2) has a diode (23) which is arranged in a bridge between a bridge point (P21) between the control device (22) and the heating resistor (20) and a second signal line (8), wherein the measuring circuit (30) additionally has a third switching device (37) which, in a first switching state for setting the operating state of the heating devices (2), electrically connects a first end tap (31A) of the voltage divider circuit (31) to a second busbar (6) to which the control devices (22) are electrically contacted, and in a second switching state for setting the DC test state of the heating band device (1), electrically connects the first end tap (31A) of the voltage divider circuit (31) to the second signal line (8), wherein in the DC test state a voltage in forward direction is applied to the diode (23). [11] Heating band device (1) according to one of claims 3 to 7, additionally comprising a third signal line (9) to which a control input (24) of each control device (22) is electrically contacted, wherein the control devices (22) switch the heating devices (2) into the operating state when a predetermined signal voltage is applied to the control input (24), wherein the measuring circuit (30) additionally comprises a fourth switching device (38) which, in the closed state, switches a first control line (39) of the measuring circuit (30) that can be connected to or is connected to a voltage source to the third signal line (9). [12] Heating tape device (1) according to one of the preceding claims, wherein the heating resistance (20) of the heating devices (2) is formed as a meandering heating conductor track (11) formed on a surface (10a) of a carrier layer (10). [13] Heating band device (1) according to claim 12, wherein at least one bridge (13; 14) is formed between two adjacent sections (11) of the heating conductor track (12) to adjust the heating resistance value. [14] Method for monitoring the functionality of a heating band device according to one of the preceding claims, comprising the following steps: Applying voltage to the heating devices (2); Comparing the measured voltage tapped off with the voltage measuring device (34) with a threshold value; and Providing an error signal if the fault voltage exceeds the threshold.

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