EP1491071B1 - Heating device with flexible heating body - Google Patents

Description

The invention relates to a heating device with one in a flexible Radiator integrated and connected via a connection cable to a supply voltage connectable electrical Heizleiteranordnung, one with this and others Elements including a control element for a heating current formed heating circuit and with one for varying the heating current and regulating the temperature the control element connected control circuit.

Such a heating device is given approximately in EP 0 562 850 A2, in particular, a circuit for protecting in the flexible radiator integrated electrical Heizleiteranordnung before an excess temperature goes. Furthermore, the drive circuit provided in this case also has a temperature control circuit on, with for maintaining a desired temperature a heating current via a control member in the form of a thyristor e.g. by means of Phase control is varied. Also other embodiments of the Control member, such as a mechanical, thermal or other electronic Switches are called. Also conceivable is a control with pulse packets.

The invention is based on the object, a heater of the aforementioned Kind of providing, in particular with regard to a safe Control and monitoring of the heating circuit offers advantages.

This object is achieved with the features of claim 1. After that it is planned that the safety circuit has a fault sensor device and in that in the heating circuit a controllable via the safety circuit additional Control member is arranged in series with the first control member, wherein the safety circuit also responds only to a fault of the drive circuit and the heating current interrupts by driving the additional control member.

With these measures, an improved error detection and improved Reaction when an error occurs.

On for misrecognition and a safe response if an error occurs to prevent a malfunction or a dangerous condition thereby favors that the security circuit has a rating section that communicates with a drive part of the drive circuit or with the heating circuit for tapping at least one characteristic signal state or more characteristic Signal state changes is in electrical communication, and that the safety circuit is formed such that upon detection of the at least one characteristic signal state or the characteristic signal state changes the additional control element for interrupting the heating current drives.

For the evaluation and control functions, the measures are furthermore advantageous, that the drive part is designed as a digital circuit part and the signal state or the signal state change at least one digital signal affect.

A secure detection is supported by the fact that the signal state or the Signal state change of two separate, in normal mode complementary or is tapped in the normal state of the same signals by means of the safety circuit.

A vorteihafter structure results from the fact that the at least one digital Signal on at least one output terminal of the digital circuit part is tapped.

A simple circuit construction is e.g. obtained by that between the Output terminal and the additional control element, a circuit part only is arranged with a capacitor and a resistor.

An inexpensive design for the construction is that the safety circuit as evaluation part has a transistor stage, the input side with a base connection and with an emitter connection or collector connection for picking up the at least one signal state or the signal state changes connected to two separate terminals of the control part is and on the output side via the collector terminal or the emitter terminal with a control terminal of the additional control element for its activation in Connection stands. The transistor can be a bipolar transistor or a Field effect transistor, in which case the base terminal, emitter terminal and Kollektoranschuss the gate terminal, drain or source connection correspond. Another semiconductor circuit arrangement is conceivable, for example with CMOS logic or analog switches.

A further favorable for the function embodiment of the heater results in that the signal state or the signal state change in the Heating circuit or in one of the drive part leading to the first control member Control branch is tapped.

An advantageous structure consists in that the safety circuit as Assessment part has a transistor stage, the input side with its base terminal is connected to the heating circuit or the Ansteuerzweig and on the output side with its emitter connection or collector connection at the control connection the additional control member is connected.

For the safe operation of the heater are still the measures of Advantage that the drive circuit further for tapping one of the Temperature of Heizleiteranordnung dependent electrical parameter over a Coupling branch is coupled to the heating circuit and a control circuit with a digitizer a digital circuit arrangement for driving the control member as a function of a deviation between an actual value and a nominal value and that the drive circuit is designed such that the drive of the control member for adjusting a set temperature of the radiator the basis of digital data formed in the digitizer stage.

To form the actual value is advantageously provided that the measured variable means a voltage divider formed in the heating circuit is tapped on the one hand with a temperature-dependent resistor forming Heizleiteranordnung and on the other hand formed with at least one resistance element. The anyway existing Heizleiteranordnung is also used as a temperature sensor.

A favorable structure of the drive circuit, in particular of the control loop results in that the measured variable is fed via a feed branch to one of the digitizing stage upstream analog timer with a resistor / capacitor circuit fed to the digitizer stage for forming a digital Actual value has a timing element and the digital actual value of an actual time to for reaching a predetermined or predefinable charging voltage of the capacitor corresponds to the setpoint value specified in the digitizing stage as setpoint value or is predeterminable, and that for heating the control of the control member as a function of a deviation of the actual time value from the setpoint time value he follows.

Further advantageous embodiments are that in the heating circuit the radiator or outside of which a fuse is arranged, and further that the heater assembly is only two out of the heater led out Heizleiterenden, which at connection points with a two-wire Direct connection via a 2-pin connector / coupling unit or a hot lead connection is connected, as well as in that the connection points lie within a cord switch housing.

Fig. 1A und 1B

schematische Darstellungen einer elektrischen Schaltung und einer abgewandelten elektrischen Schaltung einer Heizvorrichtung mit einer zusätzlichen Sicherheitseinrichtung,

Fig. 2

eine schematische Darstellung einer weiteren elektrischen Schaltung einer Heizvorrichtung mit einer abgewandelten zusätzlichen Sicherheitseinrichtung und

Fig. 3

Spannungsverläufe eines Zeitglieds, aufgetragen über der Zeit zum Herleiten eines Istwertes, Sollwertes und Referenzwertes.

The invention will be explained in more detail by means of embodiments with reference to the drawings. Show it:

Fig. 1A and 1B

schematic representations of an electrical circuit and a modified electrical circuit of a heating device with an additional safety device,

Fig. 2

a schematic representation of another electrical circuit of a heater with a modified additional safety device and

Fig. 3

Voltage curves of a timer, plotted against the time to derive an actual value, setpoint and reference value.

In Fig. 1A there is shown a heating device with a flexible radiator 1, e.g. in Form of an electric blanket, a heating pad or heat blanket, in which a Heizleiteranordnung 1.1 integrated and a fuse F1 are housed, and with a force acting on a heating circuit 3 drive circuit 2, with a heating current iH flowing through the heating circuit 3 with the heating conductor arrangement 1.1 Adjustment of a desired temperature is variable. To the electromagnetic Field regulation can thereby heat conductors with one in one direction of the current arranged inner conductor and arranged in the opposite direction External conductor be connected, as is known.

The to a supply voltage UV, for example, a mains voltage, another transformed voltage or DC voltage, connected and via Switch S1, S2 of this separable heating circuit 3 has following the Heizleiteranordnung 1.1 and the fuse F1 two consecutive Control elements THY2 and THY1 in the form of thyristors or triacs or others Semiconductor switches or electronically actuated mechanical contacts as well a voltage divider resistor R21 connected to its from the control member THY1 remote terminal is connected to ground and with the Heizleiteranordnung 1.1 forms a voltage divider. The heating conductors Rhz1, Rhz2 of the heating conductor arrangement 1.1 are preferably melted by means of a melting at a suitable temperature Isolator insulated from each other and as an inner conductor and outer conductor of a heating cord interconnected, as known per se, which also compensates of the electromagnetic field is reached. The heating conductor arrangement 1.1 is on e.g. two connection points A, B in the edge region of the flexible radiator 1 or on a short piece of cable with a plug / coupling unit in the heating circuit 3 releasably coupled or connected via this with fixed connection cables. The fuse F1 can also outside the flexible radiator 1 in the Heating circuit 3, for example, be arranged the plug / coupling unit. The Heating conductor Rhz1, Rhz2 have a temperature-dependent resistance, for example with a positive temperature coefficient (PTC effect) or negative Temperature coefficient (NTC effect), so that together with the voltage dividing resistor R21 voltage divider is temperature dependent. Several Heating circuits 3 may be provided in parallel or in series, wherein in the radiator 1 are arranged according to several heating cords.

The drive circuit 2 is connected via a coupling branch 5 for tapping by means of Voltage divider from the voltage divider resistor R21 and the Heizleiteranordnung 1.1 formed partial voltage and a Ansteuerzweig 9 to a Control input of the control member THY1 connected and has one via a Power supply 4 powered digital circuitry 2.1, for example as a microcomputer, microcontroller, special integrated circuit arrangement (ASIC), CMOS gates or the like is formed, and further in a charging branch 7 and setpoint branch 6 integrated timer from a resistor / capacitor circuit R7, C6 and a lying on the supply voltage UV another voltage divider 8 with fixed resistors R12, R15 and an adjustable Resistor P1, wherein in the positive potential terminal to the supply voltage UV another diode D2 is inserted in the forward direction. In this case, the further diode D2 is arranged so that the entire drive circuit 2 is connected via this to the supply voltage UV.

At the further voltage divider 8 is between the two fixed resistors R12, R15 for forming the set value branch 6 one with the adjustable resistor in the form of the potentiometer P1 adjustable partial voltage tapped accordingly a desired temperature of the radiator 1 is selectable. The potentiometer P1 lies between the ground-side fixed resistor R15 and Mass Gnd. The tapped at the other voltage divider 8 partial voltage is connected to the digital circuitry 2.1 to open and close to a connection switch connected controllable switch S3 to the Capacitor C6 applied. The capacitor C6 is thus with its one port via the charging resistor R7 for charging to the positive pole of the supply voltage UV and with its other connection over the controllable Switch S3 and the fixed resistor R15 and the potentiometer P1 for forming the setpoint branch 6 connected to ground, wherein the setpoint branch 6 for Forming a setpoint temporarily by means of the controllable switch S3 accordingly a set in the digital circuitry 2.1 Ansteueralgorithmus can be closed. The connected to the charging resistor R7 Connection of the capacitor C6 is also for detecting a charging voltage with an input terminal of the digital circuit arrangement 2.1 for detecting the charging voltage and feeding connected to a digitizer stage 2.11 while the other terminal of the capacitor C6 preferably to a discharge port (Discharge) of the digital circuitry 2.1 is connected, to perform a controlled complete discharge of the capacitor C6. moreover is this other terminal of the capacitor C6 via the coupling branch 5 with a resistor R14 for picking up the divided voltage across the resistor R21 of the heating circuit 3, i. a current measured variable as a function of the temperature the Heizleiteranordnung 1.1 and thus the radiator 1 connected, wherein the connection point in the heating circuit 3 between the control member THY1 and the Voltage divider resistor R21 is located. The Ansteuerzweig 9 includes a resistor R11 and R11 is connected to a control terminal Trig1 of the digital circuitry 2.1 connected to a temperature control of the radiator 1 in dependence to perform a setpoint / actual value comparison, using the digital circuit arrangement 2.1 appropriate control algorithms given or can be programmed.

Alternatively, the discharge connection Discharge can also be omitted. Instead of partial stresses can generate over the resistors R7 and R12, also corresponding from the load circuit (heating) separate DC voltages are applied, so that the resistors R7 and R12 are saved. Furthermore, different Setpoints are also specified in the digital circuit arrangement and via assigned connections are tapped, which contacted by means of switch suitable can be. This allows the resistors R12, R15, P1 and replace the switch S3. The specification of the setpoint then does not take place via the changed resistance P1, but by means of changeover. For example, for that a temperature-stabilized time clock or a reference time in the digital Circuit arrangement 2.1 are provided.

On the other hand, the digital circuit 2.1 is connected via a terminal Vcc the power supply 4 and by means of a ground terminal Gnd to ground potential placed. In addition, there is a synchronization connection Sync, a display connection Anz and a reset connection Reset further connections the digital circuit arrangement 2.1 with the power supply 4, wherein at the Sync terminal Sync a resistor R2 and to the display terminal Qty a display, for example in the form of a LED display LED and a Resistor assembly R3 are connected. The power supply 4 in turn is on the one hand to ground and on the other hand via a resistor R1 and the another diode D2 at the supply voltage UV.

In addition, in the heating circuit 3 in front of the control member THY1 in series with this an additional controller THY2, and the drive circuit 2 has one this connected safety circuit 10. The control member THY2 can thereby according to the control member THY1 as a thyristor or other electronic or electronically controllable switch may be formed or may be a form separate or an integrated part of the control member THY1.

The safety circuit 10 has a transistor stage with a PNP transistor T2 on, with its base via an RC element to a first safety connection Trig 2, with a base resistor R10 at the base and a second capacitor C5 is connected to the safety connection Trig 2, and that with his Emitter to one to the first complementary second security port Out the digital circuitry 2.1 is connected. With the collector is the Transistor T2 via a control resistor R13 to a control terminal of the additional Control member THY2 connected.

In the following, the function sequence for the temperature control will be described with reference to the in Fig. 1 shown heater and shown in Fig. 3 charging curves of the capacitor C6 explained in more detail, from which a reference value, the actual value at different Temperatures of Heizleiteranordnung 1.1 and the setpoint derived become. The reference value, the setpoint and the actual value are each made from Charging curves of the capacitor C6 determined on different circuits, which are controlled by means of the digital circuit arrangement 2.1, wherein the Charging times of the capacitor C6 to a certain charging voltage by means of a provided in the digital circuitry 2.1 digitizer 2.11 be determined. In digital circuitry 2.1 is a digital Timer provided with a fixed time clock and a counter. By the Comparison of the actual value in the form of an actual time value and the setpoint value in form a set time value is the supply of the heating current iH by means of Control member THY1, i. decided on heating or non-heating.

For the determination of the reference value is present here, for example during a negative half wave of the supply voltage UV, for example, the Mains voltage is, the capacitor C6 via the connections Actual / Ref and Discharge completely discharged. During the reference measurement are the controllable Switch S3 and the load switch in the form of the control member THY1 not activated, i.e. open. The sync terminal Sync becomes a zero voltage crossing each positive half - wave detected and after the zero crossing starts the Charging of the capacitor C6 in response to the resistors R7, R14, R21 and the other diode D2 until a digital switching level at the reference input the digital circuit arrangement 2.1 is reached. At 50 Hz mains frequency For example, the charging time of Fig. 2 is e.g. 5.8 ms, which forms the reference value.

To form the actual value, the controlled switch S3 is not activated, remains thus open, whereas the control element THY1 is actuated, i. the heating circuit 3 is closed is. Due to the flow of current through the formed by the heating conductors Heating resistors Rhz1 and Rhz2, the fuse F1, the diode D01, the control member THY1 and the voltage divider resistor R21 creates a temperature-proportional Voltage drop U21 at the voltage divider resistor R21. For example, the partial voltage in the form of the voltage drop U21 at 20 ° C heating conductor temperature approx. 1 V (peak of the positive sine half-wave) and at maximum temperature (80 ° C) approx. 0.7 V. Due to the parallel increase of the positive charging voltage to the charging resistor R7 and the raising by means of Partial voltage U21 shortens the charging process on the capacitor C6 to Reaching the switching level on a charging time or an actual time value of about 4.7 ms at 20 ° C. Changes due to the heating of the heating element assembly 1.1 to 70 ° C due to the PTC effect, the partial voltage U21 to about 0.75 V in the maximum of Sine half-wave, so the charging of the capacitor C6 takes about 5.0 ms.

To form the setpoint in the form of the setpoint time value is not activated Control member, i. with the heating circuit 3 open and on, i. closed controllable switch S3, the charging voltage of the capacitor C6 at maximum Temperature setting (80 ° C) by potentiometer P1 by approx. 0.7V (Maximum of positive half-wave) raised. This corresponds to the partial voltage U21 at maximum temperature. This results in a capacitor C6 Charging time up to the switching level of 5.1 ms (set time value at 80 ° C). The setpoint branch 6 results from the components further diode D2, resistor R7, Capacitor C6, controllable switch S3, resistor R15 and adjustable resistor P1 in conjunction with the resistor R12 of the further voltage divider 8, wherein the controllable switch S3 by means of the digital circuit arrangement 2.1 is controlled via the connection switch.

At the end of the temperature control, the reference value is first determined, After that, the setpoint and the actual value become the set time value and the actual time value certainly. By comparing the charging times to the capacitor C6, due to the derived digital data of the actual time value and the set time value is then decided on heating or non-heating. at Reaching the maximum temperature results in the same charging times on the capacitor C6 (where the sub-voltage U21 is 0.7V), i. in this case 5.1 ms. Thereafter, the control of the control member THY1 is interrupted and a Pause time of about 1 s inserted. After that, the reference, setpoint and Actual value determined within 3 mains half-waves. By another comparison is again decided on heating or non-heating. When not heating is again a break of 1 s inserted. This process is repeated.

Specifically, the comparison of setpoint and actual value in the digital circuitry 2.1 be fed to other control algorithms to the Heating current iH in the heating circuit 3 via the control member THY1 as a function of a desired temporal temperature behavior and / or depending on the type of flexible radiator 1, for example, a blanket, a Heat pad or heat bed to perform. With a microcomputer or Microcontroller, a suitable control algorithm can be easily programmed, in particular, safety regulations are taken into account can.

One way of controlling temperature is to increase the setpoint and realize a guided setpoint reduction to a nominal value. conditioned by the thermal delay of the increase of the surface temperature of the radiator 1 on the Heizleitertemperatur due to poor heat conduction of Materials of the flexible heater 1 is e.g. desirable, the temperature rise to improve. One solution to this is to set one after the Switching on the heater time-based increase of a setpoint temperature. To increase the surface temperature of an already preheated radiator to reach the setpoint for the control by an optimized Procedure specified. This can be done by determining the difference between Setpoint and actual value and a calculated temporary re-heating dependent thereon after reaching the setpoint temperature. Alternatively, a can calculated higher setpoint value for the control, e.g. from a setpoint and actual temperature comparison be fixed. So is the setpoint / actual value difference When switching on, a large setpoint increase is defined. The Elevation is then e.g. as long as constant or changed, until the Actual value coincides with the excessive setpoint. Then one starts out the setpoint overshoot derived temperature gradation. In this way results the advantage that the surface temperature shows no break-in. Is on the other hand the setpoint / actual value difference at switch-on is the same as a current one Operation, so no setpoint increase and no guided setpoint reduction carried out at nominal value. Corresponding parameters for the assessment the setpoint / actual value difference can be in the digital circuit arrangement 2.1 are stored. Depending on the type of flexible radiator 1, e.g. heating pads, Heat underblankets or thermal blankets, can also be a different calculation method be provided for the setpoint increase. This can e.g. by evaluation of a stored software or by programmed digital inputs or by time-controlled connection or switching to one other setpoint level can be realized.

The reference measurement already described can be advantageous for the detection of Errors are used. For this, the measured reference value of the charging time be compared with the setpoint and / or the actual value and on the basis of the comparison result due to previously known or stored or entered Values indicate an error of the electronics, e.g. Short circuit in the control member THY1 or be detected in connection with the controllable switch S3.

Due to plausibility comparisons, the errors can be pinpointed and used Display. The display can range from a simple light up be designed for a variable display, wherein the control means the digital circuitry 2.1 different, e.g. as a flashing warning display or may be acoustically formed.

The shutdown of the heater can by means of single or multiple timer take place, with switch-off fixed or separately switchable integrated can. During prolonged operation, a temperature reduction by appropriate Programming the digital circuitry 2.1 be provided to Skin burns due to constantly high surface temperatures of the radiator to avoid. For this purpose, from a certain setpoint temperature, a time-dependent Setpoint grading or even shutdown of the heater provided be.

By means of the display device, in this case for example as a display unit LED indicated, the different operating states of the heating devices, e.g. Setpoint reduction, timeout or the like. A user to various Way, e.g. by means of color, numbers, symbols, texts or the like. Flashing operation, changing colors, flash display or similar can be provided be and also a sound, voice or vibration display can be realized. A vibration alarm can be in the radiator or a cord switch, for example be provided until lowering the setpoint temperature, e.g. through recurring Operation a falling asleep of the user during critical phases avoid.

The safety circuit 10 shown in Fig. 1A detects the states at the safety terminals Trig 2 and Out, with the states adjacent to them digital signals are always complementary to each other and on a dynamic Control based. When not heating, the control signals are at the terminals Trig 1 and Out to logical zero and to the Trig 2 connection to logical One level. For heating, the digital signals at the terminals Out and Set Trig 1 to one and zero to Trig 2. The complementary and dynamic control of the outputs on the Out and Trig 2 outlets has the advantage that in case of failure of the digital circuitry 2.1, in particular in the form of a microcontroller in the static permanent reset state, in which all outputs are usually at one, or when a stop Program counter the heating current iH always interrupted, i. the heating is switched off becomes. In case of a program crash of the microcontroller a not allow random synchronization of the control of the control member THY1, the activation of the additional control element THY2 should only be maximum 250 μs after a zero crossing of the drive signal.

The heater shown in Figs. 1B and 2 operates except for the safety circuits 10 'and 10 ", respectively, according to the heater of Fig. 1A and in this respect is also structured accordingly.

The safety circuit 10 'of FIG. 1B is similar in construction to the one of FIG Safety circuit 10 acc. Fig. 1A, however, it is assumed that at the safety outlets Out and Trig 2 same signal states of the digital Signals are present, the control is also dynamic. Here is the Transistor T2 'designed as bipolar NPN transistor T2', wherein the collector to the out port is connected while the emitter is connected via the control resistor R13 the control terminal of the additional control member THY2 is connected. The Base of the transistor T2 'is according to the embodiment of FIG. 1A via an RC element at the other safety connection Trig 2.

The safety circuit 10 'according to FIG. 1B carries a digital circuit arrangement 2.1 Invoice in which a reset state does not affect all logic elements extends. For example, this may be the case when the drive circuit 2 separate circuit parts for the control of the control member THY1 and the additional control member THY2 in the digital circuitry has.

One opposite the safety circuits 10, 10 'other safety circuit 10 "is shown in Fig. 2. Again, the safety circuit has a Evaluation part with a transistor T1, for example in the form of a bipolar NPN transistor on. The collector terminal is connected to a supply voltage Vcc, for example, from the supply voltage Vcc of the power supply 4 is tapped while the emitter terminal as in the embodiment According to Fig. 1B via a drive resistor R13 to the control terminal of in connected to the heating circuit 3 additional control member THY2 is connected. The Base of the transistor T1 is connected via a charge branch 11 with charging resistors R5, R10 'and a diode D4 connected to the supply voltage UV of the heater, wherein between the charging resistors R5 and R10 'a connection point between the control member THY1 and the additional control member THY2 the heating circuit 3 is connected. The diode D4 is located with its anode on the Charging resistor R10 'and with its cathode at a connection point of the base branch, where the base is connected via a base resistor R4 and Furthermore, a (negative) pole of another capacitor C1, the anode of a another diode D3 and connected to ground another resistor R3 connected are. The (positive) terminal of the further capacitor C1 and the Cathodes of the other diode D3 are connected to the supply voltage Vcc.

The safety circuit 10 "of FIG. 2 is constructed as a kind of watchdog and is based on a dynamic control of the control element THY1, the actual Load switch for the heating circuit 3, in a certain duty cycle of e.g. 95% on and 5% off on a period of a few, e.g. between one and ten seconds. The safety circuit 10 "with the in the Heating circuit 3 lying additional control element THY2 is located (usually) in A condition. If a continuous activation occurs in the temperature control circuit due to the error of the control member THY1, the safety circuit recognizes 10 "with its evaluation part this state and switches the additional control element THY2 off.

In detail, the safety circuit 10 "works as follows: Normally is the control element THY1 for the temperature control in the ON state. The extra Control element THY2 is also in the on state, since the negative pole the further capacitor C1 to almost the supply voltage Vcc of the digital Circuit arrangement is 2.1 and the transistor T1 via the resistor R4 is driven and thus the drive current for the additional control element THY2 can flow. The other diodes D3 and D4 block. During the one-time from e.g. 95% is now a transhipment of the other capacitor C1, i. be negative pole is via the resistors R3, R4, the base of the transistor T1, the Control resistor R13, the control terminal (gate) of the additional control element (Thyristor) THY2, the control element (thyristor) THY1 and the voltage divider resistor R21 charged to ground.

In this case, the transistor T1 is turned on and switches the additional control element THY2 on. Thereafter, the off-time of e.g. 5% of the control element THY1, and the Voltage at the negative pole of the further capacitor C1 is restored almost the supply voltage Vcc (5V) via the charging resistors R5, R10 ' and the other diode D4 charged. That means that the additional control member THY2 always stays on. The further diode D3 prevents the Voltage at the negative pole of the further capacitor C1 becomes more positive than the positive pole.

In case of an error, such as a short circuit or continuous activation of the Control member THY1, there is no off time and the additional control member THY2 will be switched off. This happens because the voltage at the negative Pol of the other capacitor C1 by the charge voltage from the supply voltage Vcc becomes smaller and smaller on earth, with the transhipment over the Resistor R3, base resistor R4, transistor T1, control resistor R13, the additional control element THY2, the control element THY1 and the voltage divider resistor R21 takes place. If the drive voltage of the Transistor T1 to the base voltage to the transistor T1 plus the gate voltage the additional control member THY2 plus the forward voltage at the control member THY1, the transistor D1 blocks and the control of the additional control element THY2 is interrupted. As a result, the heating current is switched off and on uncontrolled overheating of the flexible radiator 1 prevented.

Claims (14)

1. Heating apparatus, having an electrical heating conductor arrangement (1.1), which is incorporated in a flexible heating body (1) and can be fitted to a supply voltage (UV) via a connecting cable, a heating circuit (3) which is formed with said arrangement and additional elements, including a first control member (THY1) for a heating current (iH), and an actuating circuit (2), which is fitted to the first control member (3), in order to vary the heating current (iH) and to regulate the temperature, and is provided with a safety circuit (10, 10'), characterised in that the safety circuit (10, 10') has an error sensor means, and in that an additional control member (THY2), which is actuatable via the safety circuit (10, 10'), is disposed in the heating circuit (3) in series with the first control member (THY1), the safety circuit (1.0, 10', 10") also responding or only responding to an error in the actuating circuit (2) and interrupting the heating current (iH) by actuating the additional control member (THY2).
2. Heating apparatus according to claim 1, characterised in that the safety circuit (10, 10', 10") has an evaluating part which is electrically connected to an actuating part (2.1) of the actuating circuit (2) or to the heating circuit (3) for picking-up at least one characteristic signal state or characteristic signal state changes, and in that the safety circuit (10, 10', 10") is designed in such a manner that, during the detection of the at least one characteristic signal state or the characteristic signal state changes, it actuates the additional control member (THY2) in order to interrupt the heating current (iH).
3. Heating apparatus according to claim 2, characterised in that the actuating part is in the form of a digital circuit part (2.1), and the signal state or the signal state change relates to at least one digital signal.
4. Heating apparatus according to claim 2 or 3, characterised in that the signal state or the signal state change of two separate signals, which are complementary during normal operation or are identical in the normal state, is picked-up by means of the safety circuit (10, 10').
5. Heating apparatus according to claim 3 or 4, characterised in that the at least one digital signal is picked-up at at least one output connection (Out, Trig 2) of the digital circuit part (2.1).
6. Heating apparatus according to claim 5, characterised in that a circuit part, having a capacitor (C5) and a resistor (R10), is fitted between the output connection (Trig 2) and the additional control member (THY2).
7. Heating apparatus according to one of claims 2 to 5, characterised in that the safety circuit (10, 10') has, as the evaluating part, a transistor stage which, at the input end, is fitted to two separate connections (Out, Trig 2) of the actuating part (2.1) by a base connection and by an emitter connection or collector connection for picking-up the at least one signal state or the signal state changes and, at the output end, is connected, via the collector connection or the emitter connection, to a control connection of the additional control member (THY2) for the actuation thereof, or has a different semiconductor circuit arrangement.
8. Heating apparatus according to claim 2, 3 or 4, characterised in that the signal state or the signal state change is picked-up in the heating circuit (3) or in an actuating branch (9) which extends from the actuating part (2.1) to the first control member (3).
9. Heating apparatus according to claim 8, characterised in that the safety circuit (10") has, as the evaluating part, a transistor stage which, at the input end, is fitted by its base connection to the heating circuit (3) or to the actuating branch (9) and, at the output end, is fitted by its emitter connection or collector connection to the control connection of the additional control member (THY2).
10. Heating apparatus according to one of the preceding claims, characterised in that the actuating circuit (2) is, moreover, coupled to the heating circuit (3) via a coupling branch (5) in order to pick-up an electrical measurement variable which is dependent on the temperature of the heating conductor arrangement (1.1) and has a regulating circuit with a digitising stage (2.11) of a digital circuit arrangement (2.1) for actuating the control member (THY1) in dependence on a deviation between an actual value and a desired value, and in that the actuating circuit (2) is designed in such a manner that the control member (THY1) for adjusting a set temperature of the heating body (1) is actuated on the basis of digital data formed in the digitising stage (2.11).
11. Heating apparatus according to claim 10, characterised in that the measurement variable is picked-up by means of a voltage divider which is formed in the heating circuit (3) and is formed, on the one hand, with the heating conductor arrangement (1.1), forming a temperature-dependent resistor, and, on the other hand, with at least one resistor element (R21), in that the measurement variable is supplied, via a supply branch (5), to an analog timing member, which is connected to the input end of the digitising stage (2.11) and has a resistor/capacitor circuit (R7, C6), in that the digitising stage (2.11) for forming a digital actual value has a time measuring member, and the digital actual value corresponds to an actual time value until a prescribed or prescribable charging voltage of the capacitor (C6) is reached, in that a desired time value is prescribed or is prescribable in the digitising stage (2.11) as the desired value, and in that, for heating purposes, the control member (THY1) is actuated in dependence on a deviation of the actual time value from the desired time value.
12. Heating apparatus according to one of the preceding claims, characterised in that a fuse (F1) is disposed in the heating circuit (3) on the heating body (1) or externally thereof.
13. Heating apparatus according to one of the preceding claims, characterised in that the heating conductor arrangement (1.1) has only two heating conductor ends, which extend from the heating body (1) and are connected at connecting points (A, B) to a two-core connecting line directly via a 2-pole plug/coupling unit or a hot lead connection.
14. Heating apparatus according to claim 13, characterised in that the connecting points (A, B) lie internally of a pendant switch housing.

Images