EP1630279B1

EP1630279B1 - High efficiency household clothes drying machine

Info

Publication number: EP1630279B1
Application number: EP04104117A
Authority: EP
Inventors: Ugo Favret; Flavio Noviello
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2004-08-27
Filing date: 2004-08-27
Publication date: 2007-02-28
Anticipated expiration: 2024-08-27
Also published as: ATE355408T1; SI1630279T1; DE602004005036D1; EP1630279A1; DE602004005036T2; ES2282800T3

Abstract

A clothes drying machine comprises a drum (1), a fan (5) blowing a first flow of drying air through a drying-air conduit (2) and a motor (7) adapted to drive said fan (5). An auxiliary resistance (10) is placed inside said conduit (8), and means are provided that are able to selectively connect/disconnect said auxiliary resistance (10), preferably said auxiliary resistance (10) may be connected in series to the electric power supply of said electric motor.

Description

The instant invention describes an improved kind of clothes drying machine, preferably of the type for use in households, which is provided with means for removing the moisture from the drying air.-
Said drying machine can be both of a conventional type, sucking the drying air from outside the drum, heating and blowing that air into the drum and finally conveying it to the outside again; or said machine can be a condenser drying machine, comprising a condenser through which there is conveyed, further to the flow of the drying air itself, a second flow of cooling air, occurring of course separately from said flow of drying air, which is taken in from the outside ambient and appropriately delivered to flow through and, as a result, cool down said condenser.
Although reference to an autonomous, i.e. self-standing clothes drying machine will be made throughout the following description, it shall be appreciated that what is set forth below may similarly be applied to and, therefore, be suitable for combined clothes washing and drying machines.
The machines, which the present invention refers to, are generally known in the art. They have on the other hand been described, along with a detailed discussion of a technical nature on the advantages and the drawbacks of a number of different variations in the design and general embodiment thereof, in the Italian patent application no. PN2003U000015 filed by this same Applicant with the title "Household clothes drying machine with improved fan", and in the European pat. Appl. n. 03028410.3, to which reference should therefore be made for brevity in this description.
In case of condenser drying machines, these are provided, further to a condenser, also with:

two distinct fans for blowing the drying air and the condenser cooling air, respectively,
a single motor adapted to drive both said fans at the same time,
said motor being adapted to be controlled so as to selectively rotate in the two opposite directions.

However, it will be readily appreciated that the present invention may be equally applied to conventional drying machines (not having a condenser and associated fans and air ducts), or to condenser-type clothes drying machines of a traditional kind, i.e. provided with a regular condenser, but lacking the other features as indicated above, although the aims and advantages pursued and reachable with the present invention would of course not be fully achieved in this case.
Therefore, for the sake of completeness and clarity the following description will be based on a condenser drying machine, being intended that this fact cannot be intended as any limitation for the present patent Application.-
Largely known in the art are clothes drying machines that operate either by condensing a flow of hot air, which is first blown into the clothes-holding drum and, while circulating therethrough, removes moisture from the same clothes, or by exhausting said flow of hot moisture-laden air directly outside.
Upon having been blown into the clothes-holding drum, the hot air causes the moisture contained in the clothes to evaporate, thereby becoming almost saturated, or even fully saturated, therewith. This hot, moisture-laden air is then pushed further by said fan, thereby creating a continuous flow that is eventually sent into an appropriate condensation arrangement, which is usually constituted by a heat-exchanger flown through - along the so-called "hot" path - by said flow of hot moisture-laden air and - along the so-called "cold" path - by a substantially continuous flow of fresh air that is taken in from the outside ambient and is exhausted again into the outside ambient upon having so flown through said heat-exchanger.
Usually, even said flow of fresh air in the so-called "cold" path is activated and maintained by a fan, which is driven in a traditional manner by the same respective electric motor, driving also the fan of the hot path and the driving into rotation of the drum.-
Largely known in the art is also the fact that, during the initial phase of the drying process, the laundry is still cold and wet, and the air blown into the drum is used almost only to heat such humidity in order to make the laundry to reach a temperature high enough to allow the humidity evaporation.-
Therefore in said phase it would be useful to exploit an additional heating resistance do speed-up the heating process and to shorten the overall cycle time.-
Moreover, during the initial phase of the drying process, just because the humidity evaporation is very low due to the low temperature, it has been experienced that an air flow having the mass flow normally given by the machine could be not necessary, as it could be accepted a remarkably reduced drying air flow without suffering any important drawback.-
As a conclusion, even the condensation process in this initial phase is almost null or very low, both because the drying air passing through the condenser is little or nothing carrying humidity, and because its temperature is still too low.-
The known solutions to overcome said drawbacks are mainly based or on the avoiding the crossing between the two air flows in the condenser, deviating with adequate means in the starting phase one of these flows, or implementing a rotation program able of driving the drum rotation in that sense corresponding to a reduced drying air flow; it is actually known that the drum rotation must be operated in the two opposite senses, in oder to avoid the laundry entangling; but that implies a corresponding opposite rotation of the fans in the respective two air paths, that however generate respective air flows that are remarkably different from a rotation sense to another.-
To sum up, no-one of the known solutions shows a kind of machine able of reducing the overall cycle time by increasing the heat introduced in the drum.-
From the documents EP 0 067 896 A, FR 2681347 A1, JP 07059995 A and JP 61103999 A it is known to mount an auxiliary heating resistor in the air conduit for the circulation of the drying air.
Said auxiliary resistor is to achieve various purposes; for instance it is to hold the heat generation rate constant, irrespective of the outside air temperature, or to simplify the electronic devices dedicated to control the drying air temperature.
It would therefore be desirable, and it is actually a main purpose of the present invention, to provide a clothes drying machine provided with at least a drum, a motor to drive in rotation the drum and possibly also both the drying-air fan and the cooling-air fan, that is capable of ensuring a standard-level drying performance, and is however capable of eliminating the above-cited drawbacks.-
According to the present invention, this aim is reached, along with further ones that will be apparent from the following description, in a clothes drying machine incorporating the features as recited in the appended claims.
Anyway, features and advantages of the present invention will be more readily understood from the description that is given below by mere way of non-limiting example with reference to the accompanying drawings, in which:

Fig. 1 shows in a symbolic way the operational schematic view of an embodiment of a machine according to the present invention,
Fig. 2 shows in a symbolic way the operational schematic view of an improvement of the machine of fig. 1,
Fig. 3 shows symbolically the electrical schematic of a device comprised in fig. 3
fig. 4 shows schematically a different embodiment of the machine represented in fig. 2,
fig. 5 shows the diagrams of cumulative amount of humidity removed and of air temperature in two compared tests in a machine according with the invention.

With ref. to fig. 1, in a clothes drying machine according to a prior-art embodiment there is provided a drum 1 adapted to hold the clothes to be dried, to which there is associated a conduit 2 for the circulation of the drying air; the latter flows also through a condenser 3, which is adapted to cause the moisture contained in the drying air flowing therethrough to condense, said condenser being furthermore flown through by a flow of "cold" air, i.e. air taken in from the outside and sent to said condenser 3 via a corresponding conduit 4.
Both conduits 2 and 4 contain two respective fans 5, 6 therewithin, which are provided to circulate the drying-air flow and the cooling-air flow, respectively. Furthermore, the shafts of said two fans 5 and 6 are connected in any of the manners known as such in the art, even via appropriate mechanisms and gears, to a single motor 7 so that the rotation of this motor causes said two fans to correspondingly rotate in a synchronous manner. This motor 7 is controlled by appropriate control means (not shown), which are adapted to let it revolve in its two possible directions of rotation; as a result, this allows said two fans to be caused to selectively rotate in either direction, but in all cases in a mutually consistent manner (i.e., when a first fan rotates in a definite direction, the second fan will always rotate in a single and sole direction; and when the first fan changes its direction of rotation, the second fan will change its own direction of rotation, too.
In the traditional mode of operation, the motor driving the fan may also be used, via appropriate motion transmission means, to also rotatably drive the clothes-holding drum.-
A main resistance 9, activated with known means and procedures, is provided inside the conduit 2.-
According to the present invention, said machine is improved in the following manner: with reference to Fig. 1, inside of said conduit 2, and preferably upstream the drum, is placed an auxiliary heating resistor 10 connected to means that will be better explained further on and that are able to selectively activate/disconnect it.-
The purpose and the working of said auxiliary resistance 10 are here explained: during the initial phase of the drying cycle, as the heating power is higher than the normal heating power supplied by the main resistance 9, said auxiliary resistance is connected so that an additional heating power is supplied having the aim of heating in an accelerated way the drying air, so that the overall time length of the cycle is shortened.
However when the humidity contained in the drum is heated at a level required to start its evaporation, then said auxiliary resistance 10 is no more required and so it can be disconnected both manually or automatically; in the latter case its switching-off may depend, for instance, on the drying air temperature, or on the time elapsed from the cycle starting time.
However said solution, albeit efficient to shorten the cycle time, does show the drawback of requiring an additional electric power, that implies an increase of the total required power supply, that on the contrary should be kept at a level as low as possible.-
In order to overcome such disadvantage, according to the present invention said auxiliary resistance 10 is associated by a switching means 30 to a circuit able to connect it in series to one connection 19 of the motor 7, and to selectively disconnect it so that the motor 7 be again supplied with its nominal voltage.- (See fig. 2)
It can be easily demonstrated that such technical solution offers some benefits that are showing synergy to each other, and however do not prevent a basically correct way of working of the machine; in the facts when said auxiliary resistance 10 is connected, the wanted advantage of an additional heating power to heat the air in the conduit 2 is achieved, but in the same time the total power taken by the machine is not increased, but on the contrary is slightly reduced, as the total impedance of the circuit comprising the motor 7 has been increased.
The effect of such an operation is that, further of increasing the total heating power, the motor 7 is supplied with a lower voltage, with a consequent slowing down both of the drum revolving speed and of the two fans speed, that therefore arouse a reduction of the mass flow in the respective conduits 2 and 4.-
However it has been practically experienced that if the activation of the auxiliary resistance 10 is made in the initial phase of the drying cycle, that would not rise any particular disadvantage, as during said phase the evaporation is very weak and so there is no need of a normal drum ventilation; furthermore a reduced air flowing through the drum doesn't prevent the heating power from reaching the laundry, but on the contrary it is increased as the hot air circulates inside the drum for a prolonged time.-
Such operation mode brings a further advantage with regard to the noise: in the facts a remarkable portion of the noise generated by a drying machine depends on the air flow speed, and it is then obvious that to a reduced fans speed corresponds a reduced mass flow, and so a lower emitted noise.-
It must be also remembered that a part of the machine noise depends on the laundry rumbling inside the drum, continuously falling down on its bottom; it is apparent that if the drum revolves at a lower speed, such noise is attenuated in a correspondent way.-
Furthermore it must be observed that, as far the condensation ability is concerned, no sensible problem is noted as the drying air going out from the drum is still cold enough and a little damp, and so the condenser effect in the initial phases is mainly negligible and is not modified even if the machine operates at a reduced speed, as just explained.-
With ref. to fig. 3, a switching means 30 is used, that is provided with three poles 12, 13 and 14, and is connected in such a way that two of its fixed poles 12 and 13 are connected to respective terminals R1 and R2 of said auxiliary resistance 10, while the third pole 13, movable between the first said two poles, is connected to an electric connection terminal 20 of said motor 7; then one of said two fixed poles, the pole 14 in fig. 2, is connected to one line of the electric A.C. power supply.-
After the initial phase, the machine must be restored to its normal configuration; to this end, first automatic control means 25 can be provided; said automatic means 25, well known in the art, are so implemented and arranged in order to activate said switch 30 so that said auxiliary resistance 10 is connected/disconnected according to pre-defined parameters or operating modes.-
For instance said resistance 10 can be connected on the start of the drying cycle and disconnected when the temperature of the drying air, as detected by a proper temp. sensor not shown, reaches a pre-defined value, or after a pre-defined time elapsed from the start of the drying cycle.-
Said first automatic means 25 may advantageously be programmed so that they selectively operate in the final phase of the drying cycle; in the facts in said phase the drying air, although very hot, may be not able to fully draw away the little residual humidity still in the laundry, and so it results very useful to be able to supply a short final over-heating to optimize the drying cycle; furthermore in this phase a too effective air ventilation is not strictly required, as the laundry is almost dried and so there is no need either to take away some remarkable amount of humidity, or to strongly condense such little humidity.-
Said first automatic means 25 can either operate autonomously, or they can be disconnected by manually activating second means 26, so to restore the normal mode of operation, should this be requested by specific requirements.-
Furthermore third means 27 can be provided that are able to exclude the automatic operation of said first means 25 and that in a fully manual way can connect/disconnect said auxiliary resistance 10 away from the related circuit.
The ways of implementation of such control means 25, 26 and 27, as well as of the means able to supply said first means 25 with the data on the elapsed time and of the temperature used to operate said auxiliary resistance 10, are generally well known and easily at the reach to any man skilled in the relevant technique of signals control and processing, and so these aspects will not be further discussed.
It was also experienced that, when the drying cycle is started with the auxiliary resistance 10 already connected, it may happen that the voltage on the motor is low enough to prevent to win the starting friction on the motor, and therefore the motor is not able to start the revolution.-
To avoid such problem, the improvement consists in programming said control means so that said auxiliary resistance 10 may be connected only after the starting of the motor revolution.-
The present invention may anyway be also embodied in a manner differing from the one described just above, in which this different embodiment is practically based on the kind of electric circuit connected to said auxiliary resistance 10.-
With ref. to fig. 4, an interrupter switch 34 is placed in series to the line "L" connected to the motor 7; the two poles 32 and 33 of said switch 34 are respectively connected to the two terminals of said auxiliary resistance 10; it is then quite clear that when the switch 34 is closed , the current flows through said same switch 34, the resistance 10 being clearly short-circuited by the same switch 34.-
The above circuit arrangement could be preferred in cases when both poles of the auxiliary resistor 10 can be connected to the line even if it is non operating.-
The essential benefit of the invention has been actually demonstrated by some compared tests, wherein it was observed that in a machine normally available in the market and using the same laundry load identically wet, and with the same setting of the drying cycle, (and so with identical tests conditions, apart the fact that the tests were carried out with and without an auxiliary resistance 10 duly connected in the drying air conduit), the difference between the two temperature rises and of the related amounts of humidity removed is shown in fig. 5 .-
Said figure appears quite clear as the accompanying information are self-explanatory; however it is here stressed that, considering the point "A" of the line 1 representing the cumulative amount of water removed in the case of auxiliary resistance non activated, and considering the corresponding point "B" of line 2 representing the same parameter but in the case of auxiliary resistance connected and activated, it turns out that the same amount, around 2800 cubic centimeters, of water condensed is being removed in the two tests respectively after 95 min., and after 88 min.-
The drying machine under test was using an asynchronous motor of 190 W, 240 Vac, and the auxiliary resistance was 70 Ohms.-

Claims

Clothes drying machine, or combined clothes washing and drying machine, comprising a drum (1) holding the clothes to be dried, a conduit (2) for the circulation of the drying air, a first fan (5) adapted to blow a first flow of drying air through said drum and into said conduit (2), a main resistance (9) placed inside said conduit (2), a motor (7) apt to selectively rotate in opposite directions said drum and said first fan (5), an electric heating auxiliary resistance (10) placed inside said conduit (2), said auxiliary heating resistance being selectively connectable, characterized in that said auxilliary heating resistance can be connected and/or disconnected in series to one line of the electric power supply of said motor (7).
Clothes drying machine, or combined clothes washing and drying machine, according to claims 1, characterized in that it comprises a means (30) of electric deviation provided with two poles, wherein a first pole (12) is connected to a first terminal (R1) of said auxiliary heating resistance, a second pole (13) is connected to one of the connection means (20) of said electric motor (7), and a third pole (14) is connected to the second terminal (R2) of said auxiliary resistance (10), said second pole (13) being selectively connectable to the first one (12) or to the third one (14) of said poles.
Machine according to any of the claims 1 or 2, characterized in that it comprises means of electric interruption, preferably an electric switch (34), placed in series to the electric power supply of said electric motor (7), said auxiliary heating resistance (10) being connected to respective two poles (32, 33) of said means of electric interruption (31).
Machine according to any previous claim, characterized in that it is provided with first control means (25) able to automatically connect said auxiliary heating resistance (10) in the initial phases and/or in the final phase of a drying cycle.
Machine according to claim 4, characterized in that it is provided with second control means (26) that are selectively actionable and that are able to switch-off the operation of said first control means (25).
Machine according to claims 4 or 5, characterized in that it is provided with third control means (27) that are selectively actionable and that are able to selectively connect/disconnect said auxiliary heating resistance (10).
Machine according to any claim 4 to 6, characterized in that said first control means (25) are able to automatically connect said auxiliary heating resistance (10) according to the air temperature inside said conduit (2) or inside said drum (1).
Machine according to any claim 4 to 7, characterized in that said first control means (25) are able to automatically disconnect said auxiliary heating resistance according to the time elapsed from a pre-defined time instant, preferably given by the cycle starting time.
Machine according to any claim 4 to 8, characterized in that said first control means (25) are able to automatically disconnect said auxiliary heating resistance (10) at the starting time of the drying cycle.