DE2643497A1 - Air drier with chamber for drying objects - has sensors detecting chamber outlet and ambient air temperature for regulating heat supply - Google Patents

Abstract

The air drier has a chamber which encloses objects to be dried. Air is blown through this chamber and heated by a regulated heater. The drier can be used for example textile fabric rapid drying. The regulator has a temperature sensor for detecting the temperature of the air leaving the chamber and the ambient temperature. A circuit is used for regulating the heater for the heat to be supplied in relation to the differences between the measured temperatures.

Description

Air dryer

The invention relates to an air dryer with a chamber in which Objects to be dried can be inputted when in use, a device for carrying out the oil of air through this Kalrsler, a device for heating the in the chamber incoming air and a control device for regulating the incoming air supplied heat.

J # n known air dryer for drying objects such as Clothing has an outer housing, a rotatable drum in the housing, a fan for sucking in air and introducing it through the housing into the drum as well as a Outlet duct for the air to escape from the drum into the surrounding area the atmosphere on. Typically such dryers have one or more electrical heating elements, which are arranged in the Lufteinqangskanal and heat the air before it enters the drum entry. conventional dryers of this type have a main switch for Switching on and off, an adjustable time element with which the operator can adjust the length of the drying time, and a heating control switch whose Position determines the energy to be supplied to the heating elements. Such a heating control switch usually operates so that a plurality of separate elements in different Way to be connected in series and / or in parallel and so the energy consumption of the Elements is varied.

Flbwülil such dryer items to be dried, such as textijien can dry very quickly, they have several disadvantages. In particular is it is not possible to regulate the drying cycle of the objects when drying is terminated. The operator is dependent on their feeling in this regard. Furthermore, these dryers usually have a very large energy consumption, even with a relatively low heating setting.

The object of the invention is to provide an air dryer as described above Create a way with which it is possible to preselect the degree of drying to be achieved and the one low <j #. ' Has power consumption.

I) i (#. ':( Aufc; al # e is curch an air dryer of the input or written type solved, according to the invention a controller for sailing the the air entering the chamber, the heat to be supplied as a function of the difference between the temperature of the air leaving the dryer and the Paun: air having.

The air dryer preferably has a control circuit which is as follows works that the heat supplied by the heating element is varied so that the Difference between the temperature.

the exiting air and the temperature of the ambient air via the Drying time remains essentially constant. Preferably the difference is between the two temperatures on the order of 0 to 2 0C, with the exiting Air has a higher temperature than the ambient room temperature.

This results in a very much reduced energy consumption per drying cycle compared to conventional drying, although a longer drying time to achieve the same degree of dryness is required.

In a preferred embodiment, the Ileizelement has one or several electrical heating elements, and the energy supplied to them is thereby varies so that the current supplied to the electrical element via a semiconductor switch, for example a silicon-controlled rectifier or oinen triac controlled will. A control circuit is provided which controls the semiconductor switch in such a way that that the difference between the temperatures of the exiting air and the room air remains substantially constant at a desired value. Preferably will the temperature of the air is measured by the fact that a temperature sensor in the Air inlet duct of the dryer is arranged, and the temperature of the exiting Air is measured by arranging a temperature sensor in the air outlet duct of the dryer will.

Since the temperature difference to regulate the degree of heating of the incoming If air is used, the dryer is independent of mains voltage fluctuations and against variations in the Loading of the drying chamber and the Type of material and moisture level of the items to be dried. Furthermore is due to the fact that the temperature of the exiting air is only slightly above the ambient temperature is ensured: 3ass the moisture in the air flow of the exiting air is reduced, eliminating the problem of condensation on different parts of the Dryer is reduced downstream of the drying chamber.

The power required to maintain the temperature difference remains essentially constant over much of the drying cycle, and against At the end of the drying cycle, the required output is constantly decreasing, as it is constantly more moisture has come out of the parts to be dried.

The steady decrease in energy consumption towards the end of the dry cycle hin allows easy control of the degree of dryness of the objects at the end of the Drying cycle by simply monitoring the required energy and the dryer is switched off when the required power falls below a predetermined level has fallen off.

The problem of dehydration, with which also the natural moisture is withdrawn from the material to be dried is greatly reduced. That too Wrinkle, which occurs in both man-made fibers and natural fibers o when drying with a conventional hot air dryer occurs, its outlet air temperature is significantly above the barely ambient temperature, is reduced.

Further features and expediencies of the invention emerge from the aim of an embodiment based on the figures. From the figures show: Fig. 1 is a circuit diagram of an embodiment of the invention; Fig. 2 is a diagram of energy required to maintain the desired temperature difference in Dependence of the time course during the drying cycle; Fig. 3 is a circuit diagram the controller of the embodiment shown in FIG. 1; and FIG. 4 is a schematic Vertical section through the dryer shown in FIG.

In the figures, a drum dryer is shown which has a blower motor 1, which drives a fan that feeds air through an inlet port 20 in the housing 21 of the drum dryer and this through the drying chamber 23 leads to an outlet opening 22 in the housing 21 of the dryer. The drum dryer is of a type in which the drying chamber 23 is a rotatable drum, in which the objects to be dried are put in, and the fan motor 1 can also give the drive for this drum in a suitable manner.

Before the air goes into the drying chamber 23, it goes into the drum dryer incoming air sucked in through the fan through a heater 2, which can be suitably heated an electrical heating element. That of the heater 2 electric power supplied from the AC power source L-N is passed through a triac 3 regulated, which operated in the well-known "Impuls-Zünd11-Weise (burst-firing mode) the keying is done by a control unit 4.

The live newspaper L is with the motor 1, the ignition device 2 and the level device 4 via a self-latching contraption 8 connected, which is suitably a rush relay, which by a Pressure switch with normally open contact 7 is brought to latch. The output lines 11 from the control device 4 can be live at the end of the drying cycle and so on unlock the locking device 8 and thus the power supply to the motor 1, the heating device 2 and the control device 4 interrupt.

Two temperature sensors 5 and 6 are provided, both resistors with negative temperature coefficients or thermocouples are, the temperature sensor 5 is arranged so that it measures the ambient temperature, and the temperature sensor 6 is arranged so that it measures the temperature of the air when it enters the drying chamber leaves. For this reason, the temperature sensor 5 is expediently in the inlet line of the dryer and the temperature sensor 6 expediently in the outlet line arranged.

The control device 4 is designed so that the speed with which the blanking pulses are delivered to the gate of the triac 3 is regulated in Relation to the difference or "error" between a required temperature difference and the actual difference in those from the timing sensors 5 and 6, respectively sampled temperatures, and the control is carried out so that the temperature difference remains essentially constant, the temperature of the exhaust air expediently 1 or 20 above the ambient temperature.

As shown in Figure 3, the control device 4 expediently a "zero voltage switch" 12 of a known type which generates output pulses, when the AC supply voltage changes polarity. These "overlapping impulses" are matched to the gate of the triac 3 via a gate 13 delivered, which is controlled in response to the temperature differential.

A comparator 15 generates a difference signal corresponding to the difference between the temperatures that are scanned by temperature sensors 5 and 6, and this difference signal is given a voltage V corresponding to a reference or desired temperature differential by the comparator 15 to generate an "error" signal compared. This error signal is used to key triac 3 so that the Heating device 2 gives off heat to the admitted air and thus the error signal remains at essentially zero.

The error signal occurring at the output of the comparator 15 is a The input of a further comparator 16 is supplied, at the other input of which the output signal a non-synchronized or free-running sawtooth generator 17 is present, which has a much longer time period than the time period of the AC power supply. The comparator 16 generates a logic ~ 1 "output when the error voltage is smaller than the instantaneous linear voltage rise, and a logic "0" if the linear voltage rise exceeds the error signal, so that it is an output pulse train generated whose pulse widths are proportional to the error signal. This pulse width modulated Signal is combined with the output pulses of the zero voltage switch 12 through the AND gate 13, so that the triac 3 is touched in the impulse fire process (burst fire) becomes that the temperature difference between the ambient temperature and the outlet temperature remains essentially constant.

With 9 is an operable by the operator quick / economy switch denotes that changes the mode of operation in which the control device 4 works. In the economy mode of operation, the control device 4 works so that the output air is kept at a temperature just a little, i.e. 1 or 2 ° C above the ambient temperature, while in the fast operating mode the control device 4 works so that the temperature difference has a much higher value, so that faster drying is achieved if this is done by the operator it is asked for. The fast mode of operation is achieved by the fact that the required Temperature difference is changed to a higher value "V1".

Figure 2 shows a diagram relating to the power required for this is that the required temperature differential is maintained in the economy mode remains, with the drying time progressing as a drying cycle. As can be seen A considerable amount of energy is initially required to compensate for the temperature difference to be maintained, since during this time (0-T1) the dryer itself, which is in this contained objects and of course the water in the articles on the Working temperature must be heated. After this heating has taken place, it follows a period (T1-T2) in which a substantially constant power is required is because the water evaporates from the items to be dried. During the final part (T2-T3) of the drying cycle takes the time to maintain the temperature difference required power quickly and finally reaches a substantially constant one low level, which indicates the performance required for the Inside of the dryer kept at the desired level above ambient temperature will.

When the drying cycle has ended, a signal appears at the output 11 of the control device 4, which causes the self-locking device 8 is unlocked and so is the power supply interrupted to the dryer and the drying cycle is ended. One way of generating the output signal 11 consists in providing a timer in the control device 4, which at the beginning of the The drying cycle begins to run and an output signal after a preset Gives time that is appropriately selected by the operator. It will, however prefers to control the degree of dryness of the items to be dried, and it can can be achieved in that the energy to be supplied to the heating device 2 or Performance monitored to maintain the required temperature difference will. As can be seen from Figure 2, the required power decreases after being exceeded of the point T2 of the drying cycle, since the remaining in the objects Moisture is reduced. In this way you can monitor the required Power and termination of the drying cycle at the moment when the required power has dropped to a predetermined level, drying the items up to to a certain degree of dryness. That of the heater 2 supplied energy is proportional to the ratio in which trigger pulses to the Gate of the triac 3, and so it is possible that from the heater 2 Energy absorbed by measuring the speed with which the triac clock pulses 3 are fed to monitor. This is made possible by the tactile impulses are fed from the AND gate 13 to an averaging circuit 18, the Output signal is fed to a threshold switch 19, which has an output pulse generated when the output of the averaging circuit 18 falls below a drops to a predetermined value.

The output signal of the threshold switch 19 is via the lines 11 fed to the locking device 8 for unlocking. The threshold switch 13 has an adjustable threshold level so that the drying cycle ends, when a predetermined degree of drying that can be set by the operator (corresponding a special level of energy consumption) is reached. The threshold of the Threshold switch 19 can either be continuously variable or by one certain range of predetermined values with the help of one of the operator actuating switch 10 be adjustable.

Claims (7)

Claims Air dryer with a chamber in which when in use Objects to be cknende can be entered, a device for passing through Air through this chamber, a means for heating those entering the chamber Air and a control device for regulating the incoming air Heat, characterized in that the control device has corresponding temperature sensors (5, 6) for sensing the temperature of the air leaving the chamber (23) and the Ambient temperature and a circuit (3, 4) for regulating the heating device (2) Amount of heat to be supplied depending on the difference between the measured temperatures having. 2. Air dryer according to claim 1, characterized in that the control device (4) a comparator (15) for comparing the measured temperature difference representing signal with a reference signal and a proportional control circuit (16), which are used to receive the comparator output signal and to regulate the energy supply is connected to the heating device (2) -l. 3. Air dryer according to claim 1 or 2, characterized in that a switch (9) which can be actuated by an operator for changing the effective value of the reference signal is provided. 4. Air dryer according to claim 2 or 3, characterized in that the proportional control circuit (16) and the comparator are calibrated so that a temperature difference of not more than 20C is maintained. 5. Air dryer according to one of the preceding claims, characterized in that that the control device has a circuit (18, 19, 10) for monitoring the heating device (2) the supplied energy or the energy consumption and to interrupt the drying cycle in the event that the energy falls below a predetermined value. 6. Air dryer according to one of the preceding claims, characterized characterized in that the heating device can be operated electrically and that the control device a triac (3) for controlling the heating device (2) supplied via the triac (3) Current and a pushbutton circuit (16, 17) for actuating the triac (3) in the pulse ignition mode in accordance with the temperature differences. 7. Air dryer according to one of the preceding claims, characterized in that that the temperature sensor (5) for monitoring the ambient temperature in the way of is arranged in the chamber (23) entering air.