IE47893B1 - Electric hairdrier - Google Patents

Abstract

In an electric hairdrier in which a heating resistor (22) arranged in the air flow from a blower motor (15) is controlled by an electronic regulating device (23), the temperature of the emerging air is manually settable. In normal operation the outlet air temperature as measured by a sensor (33) remains constant at a value determined by the setting element (32), independently of the rate of air flow. However, in the event of disturbance variable occurring at the air outlet, the resulting excess of measured over desired temperature is arranged to operate a no-voltage circuit breaker (25) whose effect is to lower the effectively commanded temperature.

Description

This invention relates to an electric hairdrier having a blower and a heating system.

Conventional electric hairdriers generally have a blower which sucks in cold air and delivers it via heating resistors. After the air has been heated by the heating resistors it is fed to the moist or wet hair and brings about the drying thereof. It is a disadvantage of known hairdriers that their heating system can only be switched either on or off.

However, electrical curling tongs have been proposed having a thermal switch and a heating element incorporated into the heating arms (';».-na» Patent Specification No. 526,415). In the case of said curling tongs it is possible to set various temperatures by means of a device which is freely accessible from the outside. Although such curling Longs already have a device which makes it possible to set various temperatures, said device is not suitable for hairdriers because it is based on the principle of the varying thermal expansion of different materials. In addition, the known curling tongs neither respond to external influences nor are they suitable for the control of an air flow temperature.

A heating element comprising a PTC resistor has also been proposed for regulating the temperature of electrically beatable curlers (U.S. Pu‘c ' Specification No. 3,689,736). Although this heating ejem< -t indeed brings about a certain regulating action, the fine.’ temperature is not variable.

Furthermore, an arrangement for controlling the temperature of electric curlers and hair dressing irons has been proposed in which a known electronic temperature regulator is connected in the heating flow circuit of a curler or iron (German Offenlegungsschrift No. 2,506,07¾). The known temperature regulator can have a thyristor or a triac control system with integrated no-voltage circuit breakers (Funk-Technik, 197^, PP. 532-53¾) 567-569, Elektronik 1975, No. 7, pp. 72-7¾). However, the known arrangement is less suitable for hairdriers with a high rate of air flow because in the case of curlers or curling irons no air is moved by means of a blower. As the known apparatus only has one output variable, i.e. the temperature, w liereas hairdriers have two output variables, i.e. the temperature and the air flow rate, blower drive problems arise in the case of hairdriers whereas this problem is not encountered with curlers or curling irons. The known arrangement does not show how such a blower drive can be combined with the temperature regulation in a circuit.

Finally, a fan unit, particularly a fan-forced heater has been proposed having a heating resistor arranged in the blower air flow and an electric motor driving the blower rotor, thermostats being provided which control the output of the heating system via a series-connected control unit (Kcjhki>i Aus'egeschrift ’'j. 2 535,853). In this fan unit, a first thermostat is arrsi ,uJ in the hot air flow of the blower and a second thermostat around which flows the ambient air is located on the fan unit casing. This is - 4 intended to unsure that, e.g. in the tropics, a lower air exit temperature is produceil than in llie polar regions. However, this apparatus has no possibility of manually adjusting the various heating temperatures. In addition, no protective measures are provided to prevent burning of the scalp.

The present invention aims to provide a hairdrier whose air outlet temperature can be adapted to the requirements of the user and which has an automatically acting '10 protection against burns.

According to the invention, there is provided an electric hairdrier having a blower and heating system, in which a heating resistor is arranged in the blower air flow and a blower rotor is arranged to be driven by an electric motor and in which at least one temperature sensor is provided which controls the output of the hunting system via an electronic regulating device, wherein the temperatur of the aii- from the hairdrier is manually adjustable to vai'ious values and in normal opei'ation remains constant at a set air temperature independently of the rate of air Flow and wherein the temperature of the air from the hairdrier is regulated downwards if the air outlet from the hairdrier is restricted.

The advantage which results from the invention is that in particular the user of the hairdrier can set a given air outlet temperature which is then maintained by the hairdrier. Thus, it is nut a question of permanently setting a given heating capacity which remains unchanged until a new setting is ?iaf··. It·, the latter case, the air temperature could incrcBst· to an inadmissible extent in the case of an accumulation of air because with a reduced air flow the heating capacity remains the same. According Lo the invention, it is the air outlet temperature which is regulated to a constant value and not the heating capacity. Thus, if the air outlet temperature increases to an inadmissible extent, the heating capacity is reduced until the original air outlet temperature has been restored.

A further important advantage of the invention is that the user of the hairdrier is protected from burns as a result of the air being too hot. If, for example, there is an accumulation of air at the outlet from the hairdrier, possibly through the user pLacing the hairdrier directly onto the hair or scalp, th.p the air outlet temperature is regulated down. Au adjustment which would only maintain the air exit tempera ture constant could not. achieve this because then e.g. the set temperature of l40°C would he maintained which could lead >o hums..

The invention will now be further described, by way of example, with reference to the drawings, in which :Fig. 1 is a side elevation of one embodiment of a hairdrier according to the invention; Fig. 2 is a plan view of the hairdrier shown in Fig.1; Fig. 3 shows a circuit arrangement for operating the hairdrier shown in Figs. 1 and 2; Fig. 4 is a block diagram of an integrated no-voltage circuit breaker; and - 6 Fig. 5 shows a circuit arrangement for a sensor monitoring system integrated into the no-voltage circuit breaker shown in Fig. 4. lief err ing to the drawings, Fig. 1 shows a hairdrier 1 which essentially comprises a handle 2 and a blower 3.

At the end of handle 2, a lead 4 is provided which serves for supplying electric power to the hairdrier. The lower end of the blower 3 has an air outlet grille 5 behind which is located the heating system (not shown).

The controls of the hairdrier 1 are located at the transition point between the handle 2 and blower 3· These comprise an on/off switch 6 which also permits the setting oi different blower motor speeds and a temperature control knob 7.

Fig. 2 shows the two control devices 6 and 7 in greater detail. It is possible to see that the switch 6 has, in alj, three positions and specifically a position 0 (off), a position i (boating stage 1) and a position 2(hea+ing stage II). The temperature control knob 7 is, However, a continuous adjustment device which can be continuously adjusted from minus” (low temperature) to plus” (high temperature) and vice versa.

Tlie slits 8 shown in Fig. 2 serve to suck in cold air.

A relatively fine-meshed grille 9 is provided immediately behind the slits 8 to prevent any hair being seized by the imp oiler.

Fig. 3 shows the electrical circuit arrangement permitting t.ic operation or ιΛι» hairdrier. 10 and 11 are - 7 the two input terminals at which there is e.g. an alternating voltage IJ = 220V. Behind input terminal 11 there is a mains switch 12 which can switch the hairdrier on and off. Parallel to the input terminals 10 and 11 and behind mains switch 12, a capacitor 13 is provided for suppressing radio interference. The upper current branch of the circuit contains a thermal circuit breaker l4 which switches off the complete apparatus in the case of overheating. The circuit breaker 14 is arranged within the hairdrier e.g. in handle 2.

The power supply for a direct current motor 15 is provided by nutans of a heating resistor lb whose upper end is connected io terminal 10 and whose lower end is connected via a diode 17 and switch 12 to terminal 11. Three leads lead away from the heating resistor l6 and are soldered to different points of said resistor. Two leads lead via, in each case, a respective diode 18,19 to one connection of the direct current motor 15, whilst the third lead leads directly to the other connection of motor 15. Both connections of tlie direct current motor 15 are interconnected via an anti-interference capacitor 20„ The already mentioned diode 17 c;>n be short-circuited by means of a parallel-connected switch 21. Thus, it is possible for motor 15 to operate in the same way as described in German Offenlegungsschrift No. 2,615,223 (Fig. 6), i.e. it can be switched from half wave operation Lo full wave operation and vice versa. 7 8θ3 p .

Tile actual heating resistor 22, i.e. the resistor used solely for beating purposes, is connected in series with a triac 23. The series circuit comprising resistor 22 and triac 23 is in turn arranged parallel to input terminals and 11. A connection leads from the lower terminal of triac 23 to a filter capacitor 2¾ and a terminal m of an integrated no-voltage circuit breaker 25· The filter capacitor 24 is connected by its terminal remote from triac 23 via a series resistor 26 to a diode 27 connected in turn to the terminal 10 via the thermal circuit breaker 14. The diode 27 serves for halving the power for the IC supply, i.e. ii is a half-wave rectifier. Terminal ji of the integrated no-voltage circuit breaker 25 is applied to the connecting line between capacitor 24 and series resistor 26.

The integrated no-voltage circuit breaker 25 has in all sixteen connections a_ - g_, whereof connection £ is connected via a protective resistor 28 to the control electrode of triac 23· Connection a is connected to terminal 11 via a capacitor 29. The capacitor 29 forms a saw-tooth voltage with a resistor 3θ between connection b and connection ji. Whereas in the present case connections c_ and 1? are only interconnected by means of a bow 31, connection d_ is connected both to connection k and to the connecting 1ine between a regulating unit resistor 32 and a thermostat resistor 33· From the other end of the regulating unit resistor 32, a connection leads to a trimmer resistor 3¾ which in turn is applied to capacitor 29 and a resistor 3547893 - 9 The latter resistor 35 is also connected to a resistor 36, a resistor 37 and connection h uf the integrated no-voltage circuit breaker 25. The resistor 35 is located between connections .h and .i and resistor 39 is located between connections p. and lu Finally, a synchronising resistor 3« is provided which is located between connection and terminal 10. Ihe resistor 3^ serves to fix the pulse width of the synchronising current.

The circuit arrangement shown in Fig. 3 functions as follows : Firstly the switch 12 is closed, i.e. in Fig. 1 switch fi is moved from the 0 position into the 1 or 2 position. If the switch 6 (Fig. J) is brought into the 1 position, motor 15 only operates at half power because the diode 17 is active. However, if the switch 6 is brought into the 2 position, the diode 17 is short-circuited with the aid of switch 21 so that the 1110 Lor 15 runs at lul I power.

On switching on switch 12 the mains voltage is also supplied to the series circuit comprising resistor 22 and Lriac 23· The power supplied by resistor 22 is dependent on how often triac 23 is triggered to its ON state hy the connection IHe no-voltage circuit breaker 25, i.e. at what time intervals the triac 23 is turned ON. The triac returns to its OFF state by natural commutation at the end of a half cycle.

'Ulus, the air temperature Is essentially regulated via the control system of the triac 23. 'Hie heating resistor 16, however, produces a basic output which can only be varied in two steps and which is generally smaller than the heating output supplied by the resistor 22. 7 893 - ιυ To what extent the t.-iac 23 is controjled up and· .IttMii is largely determined by the setting of the resistor 32 and the temperature measured by the resistor 33· As the resistor 33 is located in the lower air flow of hair5 drier 1, the temperature of said air flow is regulated.

Thus, the resistor 32 sets a particular desired value which is compared with the actual value of resistor 33 in the no-voLtage circuit breaker 25. Triac 23 is then controlled via connection j_ in accordance with the difference between the desired and actual values.

The above-mentioned protection against burning of the scalp and the like is achieved in that, with a normal air fLow rale in positions 1 or 2 of the switch 6, the ratio between the resistors 32 and 33 can fluctuate within a given range. If this ratio is significantly disturbed, this fact is noticed by the no-voltage circuit breaker 25 and it then correspondingly regulates the temperature downwards. If, for example, a desired temperature of 80°C is set by means of the control 7 and at the same time there is an ambient temperature of 20°C at the location of the resistor 33, i.e. in the vicinity of the grille 5> current initially acts on the heating resistor .22 until the thermostat resistor 33 has assumed a resistance value related to the temperature of 80°C. Thus, this resistance value is associated in fixed manner with the resistance value of the resistor 32. if, for example, the air outlet of hairdrier 1 is now kept closed, e.g. by a hand, little or no air can escape so that the remaining air is greatly heated, - ii i.e. the thermostat resistor 33 records a temperature which does not coincide with the desired value. Due to this elevated temperature its resistance value changes and consequently no longer corresponds with the previously set relationship. The integrated no-voltage circuit breaker 25 notices this disturbance and correspondingly regulates the air exit temperature downwards until the old association has been restored.

However, it is also possible for the electric lead to be interrupted in front of the thermostat resistor 33 so that there is a drift of the voltage at the resistor in the other direction. Tills is also discovered by the no-voltage circuit breaker 25 and leads to the heating capacity being regulated downwards. Thus, expressed in other terms, the no-voltage circuit breaker contains two voltage threshold values which if exceeded by the voltage of thermostat resistor 33 lead to the temperature being regulated downwards.

No-voitage circuit breakers which are able to perform the above functions are commercially available (cf. e.g. Tclefunken Semiconductor Application Report, No-voltage Circuit Breaker U 106 BS).

Fig. 4 is a block diagram of such a no-voltage circuit breaker which has the advantage that there is no deterioration of the power factor, no direct current component in the load circuit and brightness fluctuations are avoided on lamps which can be caused by the periodic switching of large loads on (he public power supply system. This is 4-7 89 3 - 12 brought about by no-voltage circuit breakers in that as far us possible they switch in the zero passage of the load current and effect power consumption according to the oscillation burst control principle, zero current being switched in during a first whole numbei* of successive voltage cycles and being blocked during a further whole number of successive voltage cycles.

The actual switching elements of no-voltage circuit breakers are thyristors and/or triacs as virtually inertia-less IO circuit breakers. The property of these components is utilised firstly by connecting through with a low driving power and secondly automatically interrupting again in the rhythm Of the mains frequency just prior to each zero passage of the current.

The no-voltage circuit breaker 25 shown in Fig. 4 has various components which will he described in greater detail hereinafter.

Electric power supply takes place across connection with which is series-connected a voltage limiter 40, In turn a voltage monitoring device 4l is connected in series with the voltage limiter 40 which may comprise e.g. a Zener diode and a countercounected diode and as a result full wave control is only released if the operating voltage exceeds-the minimum value necessary for maintaining all logic functions.

During every zero passage of the alternating voltage 25 applied to connection n via the synchronising resistor 38, a pulse of selectable width is made available at the gate 42 of the output logic. This pulse appears with corresponding input states of a blocking component which acts as a pulse barrier 43 and a sensor or pick-up monitoring system 44. This prevents a power factor______ ....... ................... ................. - Π deterioration by the control, stage. The pulse harrier 43 represents an additional safety circuit because in the case of a low-resistance connection of connection 1_ to connection in, the gate 42 ia immediately blocked.

The full wave control system comprising gates 45, 46, and 48, half-wave detector 49 and store 50 processes the ouLput data from synchronising stage 51, voltage monitoring system 4l and comparator 52 in such a way that it is only possible to transmit an even number of successive output pulses. The pulse train always starts with the positive half-wave and finishes with the negative half-wave so that no direct current component can occur in the load circuit.

The output data from synchronising stage 51, voltage monitoring system 4l and comparator 52 are therefore constantly scanned and processed in such a way that under normal operating conditions, i.e. with non-activated pulse barrier 43 and pick-up monitoring system 44, no direct current component occurs in the load circuit. The output pulses are produced by a pulse generator 53 which may contain a complementary Darlington stage.

By means of suitable HC wiring at connection g_, by operating a switch 6l, a permanent pulse switch 5^ makes it possible to activate the full wave logic system for a clearly defined period after applying the supply voltage and specifically independently of the signal from the comparator 52. Thus, connection £ provides a control input making it possible, by applying a clearly defined voltage and while bypassing the comparator input information, to force a 7893 permanent pulse at connection h for as long as the voltage at connection h does not exceed a given limit value. If the comparator input signal rises above a level given by the circuit, the logic and consequently also the output pulses are reliably blocked. This permits a programmable two-stage behaviour of the regulating system with an additional securing function in the start pulse or stage.

An internal frequency response-compensated operational amplifier 55 together with the high-resistance comparator 52 10 provides the possibility of regulation even with relatively insensitive actual value transmitters and a few additional components.

Additional functions can be realised with a saw-tooth generator 56 e.g. the period group control and proportional 15 regulation even in the case of a period duration of up to about 200 seconds using relatively small and inexpensive capacitors. In addition, the saw-tooth generator 56 can be used as a low resistance reference voltage source with a programmable level.

At connection e_ there is an internal reference voltage for comparator 52 and operational amplifier 55 whose level can be varied by wiring with a resistor. Resistors 58 serve to prepare a signal for logic output o_ and/or a pulse for output j_. An amplifier 59 is thereby subject to the action of a gate 60 which to a certain extent forms the final, element of the full wave logic system comprising gates 45, 46, 47, 48, half-wave detector 49 and store 50. - 15 In connection with the pick-up circuit and/or sensor monitoring system 44, it is pointed out that the output thereof is blocked in the case of a short circuit or interruption in the pick-up circuit if the high resistance connection It is directly connected to the pick-up. It can be used to record an extraordinary change in the value of resistor 33. By simple RC wiring between connections k and the sensor monitoring system 44 can also be used for converting the output pulse into a pulse train. This has the advantage that when controlling the triacs and thyristors by means of pulse transformers, as is conventional for potential separation purposes, higher frequency pulse groups require smaller transformers than a single pulse of the necessary pulse duration.

Fig. 5 shows in detail the pick-up or sensor monitoring system 44.

If the potential of connection k is between the two reference voltages Ugj and then transistors 62 and 63 are blocked. The base current for transistor 65 and transistor 66 then flows through resistor 64. Thus, transistors 66 and 67 are connected through and consequently so is transistor 68 which completely takes up the current supplied by the constant current source 69. Thus, transistor 70 remains blocked and has no influence on gate 42. If at point k the voltage exceeds the value of Uu, then the base current of transistor 65 is taken over by transistor 62 which is blocked and the constant current flows via tlie base-emitter space of transistor 70 which switches - ι6 through and gate 42 is blocked. However, if the potential of connection lx exceeds the value of U^2, transistor 63 becomes conductive and consequently blocks transistor 66. Thus, transistor 68 receives no further base current so that transistor 7° again switches through and blocks gate 42„ Resistors 71, 72, 73, 7¾ and diodes 75, 76, 77, 78, 79 shown in Fig„ 5 merely have series connection and rectifying functions, so that their function requires no further explanation.

Claims (8)

1. An electric hairdrier having a blower and heating system, in which a heating resistor is arranged in the blower air flow and a blower rotor is arranged to be driven by an electric motor and in which at least one temperature sensor is provided which controls the output of the heating system via an electronic regulating device, wherein the temperature of the air from the hairdrier is manually adjustable to various values and in normal operation remains constant at a set air temperature independently of the rate of air flow, and wherein the temperature of the air from the hairdrier is regulated downwards if the air outlet from the hairdrier is restricted.

2. An electric hairdrier according to claim 1, wherein the temperature of the escaping air is continuously ad j instable.

3. An electric hairdriei - according to claim 1 or claim 2, wherein a manually movable control resistor is provided for setting the air temperature.

4. An electric hairdrier according to any preceding claim, wherein a regulating device is provided for keeping the temperature of the escaping air constant, said regulating device being subject at least to the action of a desired temperature value and an actual temperature value and being arranged to adapt the actual value to the desired value. - 18 5. An electric hairdrier according to claim 4, wherein the actual value is measured by means of a thermostat arranged in the escaping air flow and wherein the desired value is set with the aid of a control resistor. 6. An electric hairdrier according to claim 5, wherein, when disturbance variables occur in the air outlet area, the air temperature is regulated downwards by two thresholds formed in the regulating device and if the signal emitted by the thermostat rises above or drops below these thresholds, less electrical power is arranged to act on the heating system. 7. An electric hairdrier according to any preceding claim, wherein the hairdrier is designed to he operated on the alternating current mains and the regulating device has a no-voltage circuit breaker. 0. An electric hairdrier according to claim 7, wherein the πο-voltage circuit breaker contains a triac and a control element. 9. An electric hairdrier according to claim 7, wherein the no-voltage circuit breaker contains a thyristor and a control element. 10. An electric hairdrier according to claim 7, wherein the no-voltage circuit breaker is arranged to operate according to the oscillation burst control principle, zero current being switched in during a first whole number of successive voltage cycles and being blocked during a further whole number of successive voltage cycles. 11. Ail electric hairdrier according to any preceding claim, wherein the heating system comprises two heating circuits, namely a main and an auxiliary heating circuit, the main heating circuit serving exclusively to heat the

5. Air whilst, in addition to heating the air, the auxiliary heating circuit also serves to operate a motor arranged to drive an impeller of the hairdrier. 12. An electric hairdrier according to claim 11, wherein the motor is a direct current motor which is arranged to

6. 10 he operated by means of a circuit arrangement applied to an alternating current circuit.

7. 13. An electric hairdrier according to any preceding claim, wherein a thermal circuit breaker is provided which is arranged to interrupt the supply of voltage if 15 the hairdrier is overheated.

8. 14. An electric hairdrier substantially as described herein with reference to the drawings.