US 3603805 A
Description (OCR text may contain errors)
United States Patent Inventor Konstantin Apel Meersburg, (Bodensee), Germany Appl. No. 840,925 Filed July 11, 1969 Patented Sept. 7, I971 Assignee Holler-Patent AG Zug, Switzerland Priority July 1 I, 1968 Germany DEVICE FOR CONTROLLING LAUNDRY DRIERS WITH MECHANICAL MOVEMENT OF THE WASHING, IN DEPENDENCE UPON THE DEGREE OF DRYING 8 Claims, 2 Drawing Figs.
US. Cl 307/1 18, 34/45, 3 i7/DIG. 3 Int. CL. F26!) 25/22 Field of Search 317/123 PL; 307/1 18; 34/45  References Cited UNITED STATES PATENTS 3,210,863 10/1965 Nye et al 34/45 3,222,798 12/1965 Thornberry et a]. 34/45 3,271,876 9/1966 Behrens 34/45 3,271,878 9/ 1 966 Martin 34/45 3,331,139 7/1967 Finnegan et a1. ....317/ l23 PL UX 3,335,501 8/1967 .lanke et al 34/45 3,417,480 12/ 1968' Thunander 34/45 Primary Examiner-Robert K. Schaefer Assistant Examiner-William J. Smith Attorney-Waters, Roditi, Schwartz & Nissen ABSTRACT: In a resistance measurement type drier control, the control circuit of the drier includes a capacitor connected to the resistance bridge electrodes and an integrator coupled 'to the capacitor, the time constants of the capacitor and integrator being related to the drum rotation time.
PATEN TED SEP 7 IHTI SHEET 2 BF 2 a w .m E 0 a Q j u l. Q a A W. m 4. u 8 Ir 3 wuflu a Tm mm .N E m 8b m P W w n L. 5 P Fm N mm rm mi 2 a h 4 2 1| L 6% E H 2 8 EA Wm DEVICE FOR CONTROLLING LAUNDRY DRIERS WITH MECHANICAL MOVEMENT OF THE WASHING, IN DEPENDENCE UPON THE DEGREE OF DRYING The invention relates to a device for the control of laundry driers with mechanical movement of the washing, in dependence upon the degree of drying.
Various control devices of the initially mentioned kind are already known. One of these known devices uses electrodes extending over the whole periphery of the drum wall for the exploration of the washing. vSuch large electrodes can be produced however only with great expenditure and therefore are very dear.
Another device makes use of electrodes of disc form. The regulating circuit pertaining thereto comprises at its input a capacitor which is chargeable through the electrical resistance of the washing. When the washing is damp and thus the capacitor is nearly fully charged up, a series-connected triode draws current. This current flows through the winding of a relay which switches the drier. This device has the disadvantage however that the moment of switching off of the drier is determined not solely by the electric resistance of the washing, but also by the time duration during which the washing bridges over the electrodes. However this time duration fluctuates very greatly, so that the degree of drying cannot be determined precisely.
A further known control device utilizes a capacitor which is accommodated in the drum. This capacitor, which is initially charged up to a specific potential, is periodically discharged through the electric resistance value of the washing in each case. If the washing is still wet, it is almost completely discharged. With increasing dryness the remaining charge becomes ever greater, it then serves as a measure for the degree of drying of the washing and for the switching off of the laundry drier. This control device also possesses the disadvantage that not only the resistance value of the washing but also the time duration during which the washing discharges the capacitor determine the degree of drying. The circuit arrangement used in this connection works very inexactly, because in order to achieve an input resistance of high ohmic value it comprises glow diodes which possess considerably fluctuating ignition voltages.
It is the problem of the invention to provide a control device which avoids the above-mentioned disadvantages of known control arrangements, which is of very simple assembly, which makes very small sensing electrodes suffice, and which controls the drier independently of the time during which the washing bridges over the electrodes.
According to the invention this problem is solved due to the fact that by means of electrodes arranged in a manner known per se in the drum, with the aid of the electric resistance of the washing which bridges over the electrodes at least intermittently, an electric potential is influenced and the resultant potentials, corresponding to the washing resistance, are stored in a storage element and in that this storage element is in connection with an integrator which in turn influences a switching element which controls the drier.
One embodiment of the invention provides that the storage element consists of a capacitor.
So that the storage element may react even to the short bridge-over times of the washing, according to the invention the charging time constant of the capacitor lies in the order of magnitude of the time of contact of the washing on the electrodes.
In order to render possible the correction of the stored potential value in the course of a few revolutions of the drum, according to the invention the discharge time constant of the capacitor lies in the order of magnitude of the drum revolution time.
According to the invention the degree of drying of the washing is influenceable by means of a variable resistor which is in series with the washing resistance.
According to the invention the potentials corresponding to the washing resistance are more expediently fed to the storage element through a rectifier.
In order to ensure high resistivity of the control device, the switching element consists according to the invention of a gasdischarge tube with ignition electrode.
Likewise according to the invention it is possible that the switching element consists of at least one semiconductor.
In order to be able to switch the drier, according to the invention it is provided that the switching element controls the current flux through the winding of a relay which switches the drier.
Furthermore according to the invention it is possible that the switching element influences a program switching mechanism which controls the drier. In comparison with the mentioned known control devices, the invention possesses the advantages that it is possible to work with relatively very small electrodes. The control device is independent of the washing contact time. The preselected degree of drying is thus reliably achieved. The use of a gas-discharge tube with ignition electrode, which per se is very cheap, leads to completely secure switching results. A program switching mechanism influenceable by the switching element offers the possibility for example after the switching off of the heating of initiating yet a further function of the drier, such as the cooling of the washing by means of cold air.
The invention will be explained by reference to two examples of embodiment represented as block circuit diagrams in FlGS. 1 and 2 of the drawing.
In FIG. 1 a rotating drum 7 is illustrated which receives the washing. Within the drum 7, for example on a rib of the drum, two electrodes 4, S of approximately the size of coins are mounted in insulated manner. The washing resistance 6 lies between the two electrodes. The electrodes are in connection with the actual control device through sliprings or other spring contacts 2, 3. The device is supplied with feed voltage through the terminals 16 and 17. The washing resistance 6 lies in series with a variable resistor l, with which the desired degree of drying is preselected.
Negative voltage peaks always occur at the point of connection between the variable resistor l and the stationary part of the spring contact 2 when the washing is in contact with the electrodes 4, 5. The potential of these voltage peaks is a measure for the washing resistance 6. This potential is stored with the aid of a peak rectifier, which consists of a rectifier element 8, a resistor 10 and a capacitor 9. Its charging time constant is here dimensioned for the shortest possible contact times (order of magnitude about one-tenth sec.). On the other hand the discharge time constant is so large that the correction of 'the stored value can take place only in the course of several revolutions of the drum, that is within a number of seconds. Thus a voltage the mean value of which corresponds to the mean washing resistance is applied to the capacitor 9. This voltage mean value is produced with an integration member, which consists of a resistor 11 and a capacitor 12 and the time constant of which corresponds to the time duration of several drum revolutions.
As switching element there serves for example a cold cathode tube 14 with an ignition electrode 18. Such tubes have the advantage that they make extremely low control power suffice and possess very precisely defined ignition voltages of the electrode 18. A semiconductor arrangement is also conceivable in place of the use of a cold cathode tube 14.
If in the course of the drying of the washing the mean washing resistance has increased so far that the voltage division between the washing resistance 6 and the variable resistor 1 corresponds to the ignition voltage on the ignition electrode 18, then the cold cathode tube 14 ignites and an apparatus 15 is energized. The apparatus 15 can be for example a relay which switches the heating of the drying apparatus or influences a program switching mechanism which in turn controls the, heating of the drying apparatus. Likewise the apparatus T5 can be part of a program switching mechanism which controls the onward stepping of the latter.
If the blocking resistance of the rectifier element 8 has a suitable value, it is possible to dispense with the resistor 10. Moreover other arrangements already known are usable for the storage or integration.
ln FIG. 2 a different electronic control arrangement for the relay 15 is illustrated, which likewise serves to control the relay 15 in dependence upon the reaching of the settable degree of drying of the washing which is to be dried in the drum, so that when the desired degree of drying of the washing is reached, the relay 1S actuates its switch 22 and switches off for example the heating and/or the drive of the drum 7 of the drying apparatus.
The primary side of a transformer 24 is connected by the connections 19 and 20 to an alternating current voltage source. Connected with the voltage terminal 20 is a control lead 26, in which the contact switch 22 of the relay 15 is situated and the terminal 21 of which is connected for example to a switch contactor (not shown) which then effects the switching off of the heating and of the drive of the drum 7. The electronic control arrangement is connected through a rectifier 23 of usual type to the secondary winding of the transformer 24 and is supplied by the latter with direct current voltage. As indicated in chain lines, the resistance of the washing 6 to be dried lies between the electrodes 4 and 5. This resistance 6, with a resistance R6, which is 750 kit in the example of embodiment, forms a voltage-divider. In this case a resistor R8 of the value of 3.6 m is associated with the washing resistance 6, so that the voltage divider formed by the washing resistance 6 and the resistor R6 does not become highly resistive. When the washing is dry the resistance 6 rises to about 100 MO. A peak rectifier serving as storage element and consisting of the diode D1 and the capacitor C3 is connected to the voltage-divider 6R6. In the example of embodiment C3 has a capacity of 0.47 of. and a resistor R9 of the value 22 M0. connected in parallel with the diode D1 serves to form a defined diode blocking resistance.
Since the peak rectifier Dl-C3 requires a very highly resistive termination (app. 100 MG), the base of a transistor Ts3, which represents an emitter follower, is connected to C3 through a resistor R of 22 MO. Two further resistors R2 of k0 and R4 of 12 k0 form a voltage-divider to which the collector of the transistor Ts3 is connected. The emitter of the transistor T53 is connected to an adjustable resistor R3 (220 kit), the tapping thereof through a further resistor R8 of 33 k0 to a Schmitt-Trigger, consisting of the transistors Tsl and T52 and a resistor R1 of 15 K0 and a capacitor C2 of 50 pf. The relay l5 lies in the emitter circuit of the Schmitt-Trigger Tsl, TsZ, so that the input resistance of Ts2 is high.
The integration takes place with the capacitor C2 and the threshold resistance of the collector of Tsl.
The function of this circuit arrangement is as follows:
With rising washing resistance 6, that is with increasing dryness of the washing, the potential drops off at the base of the transistor TsS. Thus T82 is blocked more and more. Thus the voltage rises on C2. When the desired dryness is achieved, Tsl opens, so that the relay 15 is strongly energized and pulls up and actuates the switch 22. Then by the actuation of the switch 22, by known electric switching means, the heating and the electric drive of the drum 7 are switched off.
1. A control device for controlling in dependence upon degree of drying a laundry drier which provides mechanical movement of objects to be dried, said drier including a rotatable drum, said control device comprising a source of an electric potential, electrodes arranged in said drum and coupled to said source to influence said potential, said objects having a resistance which at least intermittently bridges the electrodes, a capacitor coupled to the electrodes and adapted to store potentials indicative of said resistance, an integrator coupled to said capacitor, a switch element, which controls the drier, coupled to and controlled by said integrator, wherein the charging time constant of said capacitor is in the order of magnitude of the times of contact of the said objects with the electrodes, wherein the discharge time constant of the capacitor is in the order of magnitude of the drum rotation time, and
wherein the time constant of the integrator is greater than the period of rotation of the drum.
2. A control device according to claim 1 comprising a variable resistor in series with the resistance of said objects to control degree of drying.
3. A control device according to claim 1 comprising a rectifier including a diode and a resistor connected thereto and wherein the potentials corresponding to the resistance of said objects are supplied to the said condenser through said rectifi- 4. A control device according to claim 1 wherein the switch element is a gas discharge tube including an igniting electrode.
5. A control device according to claim 1 wherein the switching element includes at least one semiconductor.
6. A control device according to claim 1 comprising a relay including a winding and wherein the switching element controls the flow of current through the winding of said relay for controlling the drier.
7. A control device according to claim 1 comprising a program switch and wherein the switching element controls said program switch device for controlling the dryer.
8. A control device according to claim 1 wherein the in tegrator includes a resistor and a condenser connected thereto.