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(11) | EP 1 997 951 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Laundry machine |
| (57) A laundry machine (1) having: a revolving laundry drum (5) having a front access
opening; an electric device fitted to the drum (5); and an electric generator (22),
which is fitted the drum (5) and uses rotation of the drum (5) to generate the electric
energy necessary to operate the electric device.
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TECHNICAL FIELD
[0002] The present invention may be used to particular advantage in a laundry drying machine having a wireless laundry humidity sensor, to which the following description refers purely by way of example.
BACKGROUND ART
[0003] A standard home tumble laundry drying machine condenses a stream of hot air blown into a drying drum and which removes moisture from the laundry; and the front access to the drum is closed by a hinged panel-type front door. More specifically, a known laundry drying machine comprises a ventilation system (i. e. usually a blower comprising a fan and an electric fan motor) and a heating arrangement, which draw air from the outside and, via an appropriate conduit arrangement, heat and blow the air into and through the laundry drying drum. The hot drying air is then either exhausted directly from the drying machine or fed to condensing means to condense the moisture collected in the hot air.
[0004] In the past, the duration of a drying cycle was constant and predetermined. However, the weight and initial humidity of the laundry to be dried are variable, so that a drying cycle of fixed duration may be either too short (i.e. at the end of the drying cycle, the laundry is still too damp and the drying cycle therefore ineffective) or too long (i.e. the drying cycle has used too much energy and is therefore inefficient).
[0005] A modern tumble drying machine normally employs a sensor to measure the relative humidity of the laundry during the drying cycle and to stop the drying cycle when the humidity of the laundry reaches a given value depending on the drying cycle selected by the user. The most effective way of measuring humidity is a direct measurement of the conductivity of the laundry. Various solutions are already marketed, which measure the conductivity between the drum and metal inserts fixed to the drum outlet or the lifters, or in which the drum is divided into two halves, and conductivity measured in between.
[0006] A limitation of the above known methods lies in the restrictions imposed on the drum which, being a component of the measuring system, must be made of any conductive material (e.g., stainless steel), and cannot be made of plastic, which is insulating, or lined with soft materials (such as thin silicone layers), which are also insulating. Consequently, the above known methods cannot be used in a tumble drying machine, in which "gentle treatment" of the laundry is achieved by lining the drum with soft materials.
[0007] Furthermore, when the drum is a component of the measuring system, the electric signal for measuring the conductivity of the laundry must be transferred from the rotating drum to an external fixed control unit by means of brushes sliding on a metal ring. The brushes, however, have a relatively short working life and must therefore be replaced frequently, and are potentially noisy, due to brush creep-generated noise. The metal ring may also have a relatively short working life due to oxidation.
[0008] To eliminate the aforementioned drawbacks, it has been proposed to determine laundry humidity by measuring the temperature and/or humidity of the drying air from the drum. Indirect measurement of laundry humidity, however, is not very stable or precise, by being affected by numerous external parameters (for example, ambient temperature, laundry load, and air course).
[0009] To partially eliminate the aforementioned drawbacks, and so permit unrestricted design of the drum, a new socalled "Limited Conductimetric System" has been proposed, based on a pair of small electrodes fixed to a non-moving part of the machine, e.g. the inside of the door. The "Limited Conductimetric System", however, has a number of disadvantages: due to the limited contact surface between the electrodes and the laundry, this system is fairly unreliable in stopping the drying cycle in time, especially with small loads (for example, of less than 1 kg) and damp cycles (for example, a final humidity of over 3-4%). Even with standard loads and dry cycles, in some cases, problems may arise because the end-of-cycle condition is not totally repeatable. Tests show that a tumble drying machine using the "Limited Conductimetric System" rarely stops a drying cycle with less than a 1 kg load in time; and, for damp cycles, even a 2 kg load may be an issue.
DISCLOSURE OF INVENTION
[0010] It is an object of the present invention to provide a laundry machine, designed to eliminate the aforementioned drawbacks, and which is cheap and easy to produce.
[0011] According to the present invention, there is provided a laundry machine as claimed in the accompanying Claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:
Figure 1 shows a schematic side view of a laundry drying machine having a wireless laundry humidity sensor in accordance with the present invention;
Figures 2 and 3 show schematic views of the Figure 1 wireless laundry humidity sensor in two different working configurations.
PREFERRED EMBODIMENTS OF THE INVENTION
[0013] Number 1 in Figure 1 indicates as a whole a laundry drying machine comprising a casing 2 resting on a floor 3 on a number of feet 4. Casing 2 supports a revolving laundry drum 5 which rotates about a horizontal rotation axis 6 (in alternative embodiments not shown, rotation axis 6 may be tilted or vertical), and front access to which is closed by a door 7 hinged to a front wall of casing 2. Drum 5 is rotated by an electric motor 8, and is fed through with a stream of drying air fed into drum 5 by a centrifugal fan 9 and heated by heating elements 10.
[0014] The moisture in the laundry in drum 5 is released by evaporation to the stream of hot drying air; and the moist hot air from drum 5 is piped to a condenser 11, which is cooled by a stream of relatively cold air drawn in from the outside by a centrifugal aspirator 12.
[0015] In condenser 11, the vapour in the stream of hot air is condensed to liquid by cooling, and collects in a condenser reservoir 13; the dry air from condenser 11 is drawn by fan 9 and fed back into drum 5, subject to reheating by heating elements 10; and the outside air used for condensation is exhausted.
[0016] The condensation collected in condenser reservoir 13 is pumped by a pump 14 into a condensation tank 15 fitted to door 7 closing the loading opening of drum 5 and located at a higher level than condenser reservoir 13; and, when condensation tank 15 is full, a known level sensor (not shown) is activated to stop drying machine 1. Operation of the drying machine is controlled by an electronic control unit (or programmer) 16 operated by buttons or knobs 17 on a front control panel 18.
[0017] Electronic control unit 16 receives a humidity measurement of the laundry inside drum 5 during a drying cycle from a humidity sensor 19 fitted to drum 5 and comprising a wireless transmitter 20, which transmits the laundry humidity measurement to a wireless receiver 21 connected to electronic control unit 16. In different embodiments, wireless transmitter 20 and wireless receiver 21 communicate, for example, by radio waves or optic (infrared) signals.
[0018] Laundry drying machine 1 comprises an electric generator 22 fitted to drum 5, and which uses rotation of drum 5 to generate the electric energy necessary to operate humidity sensor 19. Electric generator 22 is preferably an electromagnetic generator, and comprises a coil 23; and a magnetic mass 24 located inside coil 23 and movable along coil 23 between two limit positions (shown in Figures 2 and 3) defined by two mechanical stops 25 and 26. Magnetic mass 24 moves freely inside coil 23 between the two limit positions, and is moved cyclically inside coil 23 between the two limit positions by force of gravity and rotation of drum 5.
[0019] In a first angular position of drum 5 shown in Figure 2, coil 23 is in an upright position, in which mechanical stop 25 is above mechanical stop 26, and magnetic mass 24 drops by force of gravity onto mechanical stop 26; in a second angular position of drum 5, 180° from the first angular position and shown in Figure 3, coil 23 is in an upright position, in which mechanical stop 26 is above mechanical stop 25, and magnetic mass 24 drops by force of gravity onto mechanical stop 25. Rotation of drum 5 causes a cyclic change in the orientation of electric generator 22, so that coil 23 moves cyclically between the Figure 2 and 3 upright positions, and magnetic mass 24 moves cyclically inside coil 23 between the two limit positions by force of gravity.
[0020] As magnetic mass 24 moves inside coil 23, a voltage is present at the ends of coil 23 to electrically power humidity sensor 19. In a preferred embodiment, at least one condenser 27 (or any other kind of device for accumulating electric energy) is connected to the ends of coil 23 to accumulate the electric energy generate by coil 23 and to stabilize the voltage value.
[0021] As shown in Figure 1, humidity sensor 19 comprises a measuring unit 28; and a pair of electrodes 29 connected electrically to measuring unit 28. The resistance/conductivity of the laundry inside drum 5 is measured between the two electrodes 29 and used to determine laundry humidity in known manner. In different embodiments, the two electrodes 29 are defined by respective electrically insulated portions of drum 5 (in which case, drum 5 must be made of any conductive material, and cannot be lined with soft materials), or are defined by conductive (normally circular or arc-shaped) bodies fixed to the inside of drum 5 (in which case, drum 5 may be made of plastic or lined with soft materials).
[0022] In other words, in a preferred embodiment shown in the attached drawings an electric device (humidity sensor 19) is fitted to drum 5 and receives electric energy from electric generator 22. According to different embodiments, other kinds of electric devices may be fitted to drum 5; for example, a light source (for example one or more LED devices) for illuminating the drum 5 may be fitted to drum 5. Preferably, drum 5 comprises a number of lifts (axial ribs for lifting the laundry during the rotation of drum 5) and the light source is integrated in at least one of the lifts.
[0023] Of course electric generator 22 may be applied to any kind of laundry machine having a revolving drum and an electric device fitted to the revolving drum.
[0024] Laundry drying machine 1 as described above has numerous advantages, by being cheap and easy to produce, by effectively and efficiently determining laundry humidity by direct measurement of the electrical conductivity of the laundry, and by imposing no restrictions on the drum, which may be made of any material, including plastic, and may be lined with soft materials (such as thin silicone layers). Furthermore, laundry drying machine 1 as described above has no brushes (no brush wear, no brush creep-generated noise produced, no contact oxidation problems). No external voltage is applied to drum 5 and thus this solution is the safest for the users. Finally, wireless laundry humidity sensor 19 as described above is self-powered electrically, and therefore has no electric battery (no battery change required).
1. A laundry machine (1) comprising:
a revolving laundry drum (5) having a front access opening;
the laundry machine (1) being characterized in comprising:
an electric device fitted to the drum (5); and
an electric generator (22), which is fitted the drum (5) and uses rotation of the drum (5) to generate the electric energy necessary to operate the electric device.
2. A laundry machine (1) as claimed in Claim 1, wherein the electric generator (22) is
an electromagnetic generator.
3. A laundry machine (1) as claimed in Claim 2, wherein the electric generator (22) comprises
at least one coil (23); and a magnetic mass (24) located inside the coil (23) and
movable along the coil (23) between two limit positions.
4. A laundry machine (1) as claimed in Claim 3, wherein the magnetic mass (24) is freely
movable inside the coil (23) between the two limit positions; and rotation of the
drum (5) causes a cyclic movement of the magnetic mass (24) inside the coil (23) between
the two limit positions.
5. A laundry machine (1) as claimed in Claim 3 or 4, wherein the coil (23) comprises
two mechanical stops (25, 26), each of which limits movement of the magnetic mass
(24) and defines a respective limit position.
6. A laundry machine (1) as claimed in Claim 2, 3 or 4, wherein the electric generator
(22) comprises at least one device for accumulating electric energy connected to the
ends of the coil (23) to accumulate the electric energy generate by the coil (23).
7. A laundry machine (1) as claimed in Claim 6, wherein the device for accumulating electric
energy is a condenser (27).
8. A laundry machine (1) as claimed in any of Claims 1 to 7, wherein the electric device
fitted to the drum (5) is a humidity sensor (19) for measuring the humidity of the
laundry inside the drum (5).
9. A laundry machine (1) as claimed in Claim 8 and comprising an electronic control unit
(16) for controlling operation of the laundry machine (1) and receiving the laundry
humidity measurement from the humidity sensor (19); the humidity sensor (19) comprises
a wireless transmitter (20) which transmits the laundry humidity measurement to a
wireless receiver (21) connected to the electronic control unit (16).
10. A laundry machine (1) as claimed in Claim 8 or 9, wherein the humidity sensor (19)
comprises two electrodes (29) on the drum (5), and a measuring unit (28) connected
to the two electrodes (29) to measure the resistance/conductivity between the two
electrodes (29).
11. A laundry machine (1) as claimed in Claim 10, wherein the two electrodes (29) are
defined by respective electrically insulated portions of the drum (5).
12. A laundry machine (1) as claimed in Claim 10, wherein the two electrodes (29) are
defined by conductive bodies fixed to the inside of the drum (5).
13. A laundry machine (1) as claimed in any of Claims 1 to 7, wherein the electric device
fitted to the drum (5) is a light source for illuminating the drum (5).
14. A laundry machine (1) as claimed in Claim 10, wherein the drum (5) comprises a number
of lifts; the light source is integrated in at least one of the lifts.
15. A laundry machine (1) comprising:
a revolving laundry drum (5) having a front access opening;
a humidity sensor (19) for measuring the humidity of the laundry inside the drum (5); and
an electronic control unit (16) for controlling operation of the laundry machine (1) and receiving the laundry humidity measurement from the humidity sensor (19) ;
the laundry machine (1) being characterized in that the humidity sensor (19) is fitted to the drum (5), and comprises a wireless transmitter (20) which transmits the laundry humidity measurement to a wireless receiver (21) connected to the electronic control unit (16).
16. A laundry machine (1) as claimed in Claim 15, wherein the wireless transmitter (20)
and the wireless receiver (21) communicate by radio waves.
17. A laundry machine (1) as claimed in Claim 15, wherein the wireless transmitter (20)
and the wireless receiver (21) communicate by optic signals.
18. A laundry machine (1) as claimed in Claim 15, wherein the wireless transmitter (20)
and the wireless receiver (21) communicate by infrared optic signals.