DE69616392T2 - Process for washing in a washing machine - Google Patents

Description

The invention relates to a washing method for washing machines.

It is well known that washing machine manufacturers are constantly striving to produce machines that, while maintaining their performance, enable savings in terms of operating costs, i.e. a reduction in the consumption of energy, water, detergents and additives.

US-A-3,388,410 to Marshall describes a washing method in which, during the entire washing time and also during the entire rinsing time, cycles are alternately run through in which the drum of the washing machine containing the laundry to be washed can operate at a high speed and cycles are provided during which the drum can operate at a lower speed. speed. The high speed must be sufficient so that the centrifugal force acting on the laundry is greater than gravity to keep the laundry adhering to the wall of the drum (a speed of between 100 and 200 rpm), while in cycles where the drum operates at a low speed (45 rpm) the laundry falls back to the base of the drum itself. The soapy washing solution or rinse water is drained from the base of the washing machine's tub (in which the drum is located) and is constantly sprayed into the drum via nozzles by means of a circulating pump. During the rotation of the drum at high speed, a ring of washing solution or water is therefore formed in which the laundry is constantly immersed.

Washing and rinsing at high speed with laundry stuck to the drum wall and spraying the soapy solution or recycled rinse water improves the efficiency of the washing and rinsing phases. Furthermore, recycling the soapy solution or rinse water allows the amount of water used to be reduced to a certain extent.

Furthermore, the amount of water supplied to the washing tub must always be sufficient to ensure that a certain amount of water always remains in the tub during circulation in order to prevent cavitation in the circulation pump. This can occur more easily during cycles in which the drum rotates at a low speed.

In Marshall's patent, this difficulty is solved by making the trough very deep and by feeding in a large amount of water. At the time of Marshall's patent, reducing water consumption was not a crucial concern.

In the European patent application EP-A-0 404 047 to Vellati a washing process is described in which during at least part of the washing time and possibly the rinsing time the drum of the washing machine is rotated at a speed equal to or higher than that which causes the laundry to be washed to stick to the wall of the drum. During each rotation of the drum the laundry to be washed contained therein is temporarily immersed and at least partially immersed in the soapy solution or the rinsing water contained in the washing tub, the quantities of which are such that the base of the drum is always immersed therein.

Since even when rotating at a high speed the drum is always partially immersed in the soapy solution, an excessive amount of foam is formed.

Washing processes for washing machines are also known in which the water previously introduced into the washing drum of the washing machine is circulated through a detergent container and the soapy solution thus obtained is then fed into the washing tub to spray the laundry to be washed. Some of these washing processes, which do not involve cycles with a high-speed rotary movement as in the above Marshall and Velatti patents, are described in Italian patent application No. M192A002562, filed on November 9, 1992.

In addition to a certain reduction in water consumption, these procedures also enable better use of the detergent and thus a reduction in detergent consumption. However, the amount of water introduced into the wash tub must in any case ensure that cavitation phenomena are not triggered in the circulation pump during circulation.

Taking into account the prior art described above, the invention aims to provide a washing method which utilizes the conventional principle of rotating the drum at high speed and circulating the water, and which enables a required amount of water to be reduced in comparison with the conventional washing methods described above.

According to the invention, a washing method is provided for a washing machine with at least one washing phase comprising a high-speed working cycle with water recirculation, during which a drum containing the laundry to be washed and rotatably housed in a washing tub to which fresh water has previously been supplied is caused to rotate at a first speed sufficiently high to generate a centrifugal force causing the laundry to be arranged along the circumference of the drum and, at the same time, the water contained in the washing tub is taken out of the tub and reintroduced therein by spraying at a central part of the drum, and a subsequent low-speed working cycle during which the drum is caused to rotate at a second speed lower than the first speed and to allow the laundry to be mixed again while substantially interrupting the water recirculation, which is characterized in that the high speed water recirculation operating cycle has a duration limited to the time required for complete removal of a detergent from a detergent tank, and during the high speed water recirculation cycle, a portion of the water removed from the trough is caused to pass through the detergent tank and subsequently be reintroduced into the trough.

The high speed or high rpm may be between 100 and 150 rpm, and the duration of the high speed and water circulation cycle is preferably about 2 minutes.

In contrast to the washing processes according to the Marshall and Velatti patents, the process provides for the drum to rotate at high speed only during a short initial period of the washing phase, in order to cause the laundry to adhere to the walls of the drum and at the same time to circulate the washing water. Part of the water supplied passes through the detergent container so that it mixes with the detergent contained therein and then this mixture is introduced into the tub. Another part of the water is introduced into the drum by spraying, causing the laundry to be washed very quickly, and this water then quickly returns to the washing tub.

In this way, an optimal washing effect can be achieved together with an appropriate use of the detergent, which mixes quickly with the washing water.

Even better results are achieved in a preferred embodiment of the invention if, immediately after the usual water supply to a predetermined level, a considerable washing cycle is carried out at a low speed, during which the laundry absorbs the water, thereby reducing the level, and a suitable pressure switch is provided for a further water supply in order to bring about a return to the predetermined level. In this case, a total amount of water is supplied which is equal to the minimum amount necessary for the respective amount of laundry.

The amount of water circulated is thus reduced and consequently it is possible to reduce the amount of water to be supplied and at the same time ensure that no cavitation phenomena are triggered in the circulation pump. Reducing the amount of water supplied therefore results in a reduction in energy consumption for heating and a reduction in the amount of detergent.

In a further preferred embodiment according to the invention, the washing method further comprises at least one rinsing phase, which also includes a short working cycle with a high speed and water circulation, during which the drum rotates at a first speed and the water contained in the trough is simultaneously circulated and partly passed through a container for a rinsing additive and then again introduced into the trough. Furthermore, this water is partly injected into the trough into a central region of the drum by means of spraying.

A water supply that can be automatically controlled according to the amount of laundry is therefore also maintained during rinsing.

Thanks to this design, it is possible to limit water consumption even during rinsing. Furthermore, thanks to the fact that the water is sprayed during the rotation of the drum at high speed, it penetrates very deeply between the fibers of the laundry, so that any remaining detergent residue can be rinsed out to a greater extent.

Further details, features and advantages of the invention emerge from the description of preferred embodiments as non-limiting examples with reference to the accompanying drawings. In these:

Fig. 1 shows schematically and in section a first preferred embodiment of a washing machine in which the washing method according to the invention is used;

Fig. 2 is a schematic view of the washing machine along the section line II-II in Fig. 1;

Fig. 3 is a detailed sectional view of a device for diverting the circulating flow of the washing machine in Fig. 1;

Fig. 4 and 5 are two views of a nozzle for introducing the washing liquid and the drum of the washing machine in Fig. 1;

Fig. 7, 8 and 9 show a washing phase, a rinsing phase and a pre-wash phase of a washing process according to the invention, respectively;

Fig. 10 shows schematically and in section a second preferred embodiment of a washing machine in which the washing method according to the invention is used;

Fig. 11 is a detailed sectional view of a device for deflecting the outlet flow of the washing machine according to Fig. 10.

Fig. 1 shows a first preferred embodiment of a washing machine in which the washing method according to the invention is used. The washing machine has, in a manner known per se, a frame 1 in which a washing tub 2 is accommodated. The tub 2 rotatably accommodates a drum 3. Heating resistors 40 are provided on the bottom of the tub 2.

The bottom of the trough 2 leads via a pipe 4 to an outlet pump 5 (which can be seen in Fig. 6), to the outlet of which an outlet pipe 7 is connected. The inlet of the outlet pump 5 also leads via a pipe 8 to the inlet of a circulation pump 9, the outlet 10 of which is connected to a pipe 11 (Fig. 2). The latter pipe is in turn connected to a deflector 12, which can be seen more clearly in Fig. 3 and is essentially a "Y"-shaped Connection of two lines 13 and 14. The lines 13 and 14 have different diameters so that a division into different liquid flows takes place starting from the line 11. A larger diameter line 15 is connected to the line 13, which in turn is connected to a nozzle 16 which is arranged inside a basin 17 in which detergent is contained. A smaller diameter line 18 is connected to the line 14, which in turn is connected to a spray nozzle 19 which is arranged inside the trough 2, as can be seen in detail in Figs. 4 and 5. If one takes a pump 9 for circulation with a flow rate of about 18 liters per minute, the portion of water delivered to the nozzle 19 is about 10 to 11 liters per minute, while the remaining part of 7 to 8 liters per minute is fed into the basin 17.

The nozzle 16 can be moved horizontally and can optionally be arranged in separate chambers containing detergents or additives 22, provided in a series of containers in the basin 17. The movement of the nozzle 16 takes place in a manner known per se by means of a lever 23 which is hinged at 24 to the frame 1 and actuated by means of cams 25 of a timer 24, as described for example in the Italian patent application No. M192A002562 of the same applicant.

Also, a water supply line 20 goes into the basin 17 and is connected externally to a water supply connection point (not shown). Connected to the bottom of the basin 17 is a line 21 which goes into the wash tub 2.

A washing method according to the invention comprises, in a manner known per se, a prewash cycle (Fig. 9), an actual wash cycle (Fig. 7) and a rinse cycle (Fig. 8). The prewash cycle is optional and does not need to be run through.

The washing cycle comprises three phases L1, L2 and L3 (Fig. 7). The timer 24 enables the washing cycle to be started from a point A, whereby phases L1, L2 and L3 (first washing program) are run through automatically and in sequence. The washing cycle can also be started from point B, in which case phases L2 and L3 are run through in sequence (second washing program). Furthermore, the washing cycle can start at a point C, whereby only one phase L3 (third washing program) is run through.

Phase L1 comprises an initial cycle for feeding fresh water into the washing tub 2 (which is indicated by C in Fig. 7), with reference to the washing machine previously described. The water enters via the supply line 20, flows into the basin 17 without taking up detergent and from there into the tub 2 via the line 21, so as to wet the laundry contained in the drum 3 and to be washed. A pressure switch (not shown but known per se) automatically shuts off the water supply via the supply line 20 when a predetermined water level in the tub 2 is reached. This can be in a range between 20 and 25 mm measured from the bottom of the drum (levels 41 and 42 in Fig. 1).

After the water supply cycle, a first working cycle L begins, which lasts about 4 minutes, and during which the drum 3 performs a rotational movement at a relatively low speed or rpm (typically about 50 to 60 rpm). This rpm assists in mixing the laundry in the drum 3, which is thus wetted and absorbs water. The subsequent reduction in the water level in the trough 2 causes a further triggering of the pressure switch, so that again a further water supply takes place from the line 20 directly into the trough via the line 21 in order to bring the water back to the predetermined water level. In this way, the amount of water introduced into the trough is always based on the amount of laundry contained in drum 3. During the first working cycle L, the heating elements 40 are also activated.

After the first working cycle L, a high speed and agitation working cycle (R in Fig. 7) begins with a rotational movement of the drum at a speed (G in Fig. 7) of between 100 and 150 rpm (preferably 120 rpm). During this cycle, the circulating pump 9 is activated, which acts to introduce water from the trough 2 and to direct it via the lines 11, 13 and 15 to the nozzle 16, in the meantime positioned by means of the lever 23 on a first detergent container 22. The detergent is thus entrained by the circulated water and enters the trough 2 via the line 21. At the same time, the circulating pump 9 injects water directly into the trough 2 in the central area of the drum 3 via the lines 11, 14 and 18 and the spray nozzle 19 in order to spray the laundry. The centrifugal force generated by the rotation of the drum at the high speed described above causes the laundry contained in the drum 3 to adhere to the walls thereof, so that a space is created in the central region of the drum 3 in which water can be injected through the nozzle 19 to evenly wet the laundry. Since part of the water is circulated during this phase, the water level in the trough 2 remains at a level between the levels 42 (tangential to the drum 3) and 43, as shown in Fig. 1. As can be seen from the drawing, the heating resistors 40 are always covered and there is sufficient water to avoid triggering a cavitation phenomenon in the pump 9. This is made possible by the fact that, thanks to the rotation of the drum 3 at the high speed described above, the liquid injected through the spray nozzle 19 flows quickly over the laundry and quickly returns to the trough 2. Consequently, it is possible to reduce the amount of water to be introduced into the trough 2. Furthermore, since the drum 3 is not immersed, even partially immersed, in the water on the bottom of the trough 2 during the rotational movement at high speed, no foam can be formed. This cycle must be carried out long enough to ensure that the Detergent is completely removed. Tests have shown that two minutes are sufficient for this.

After the high speed and agitation cycle, a second work cycle L is carried out, which is similar to the first work cycle L, but lasts approximately 14 minutes. At the end of this second work cycle, the first phase L of wash cycle 1 is completed.

The second phase L2 coincides with the first phase L1. However, when the first phase has been carried out, the water supply (cycle C) which was foreseen at the beginning of the second phase L2 does not occur and the first working cycle L of the second phase L2 begins immediately and during this phase the water level remains constant.

The third phase L3, in a similar way to the first phases L1 and L2, comprises an initial cycle C for supplying water (a supply which is not carried out if the second phase L2 has been immediately completed), a first working cycle L with a relatively low rotation speed of the drum 3, which lasts about 4 minutes, a working cycle of about 2 minutes with a high rotation speed of the drum (G) and a simultaneous circulation of the water (R). The third phase is not carried out if the temperature of the water heated in the previous phases reaches about 70ºC. This temperature is considered safe in the event that the detergent dispenser accidentally opens.

This condition is monitored by means of a thermostat sensor. This is followed by two working cycles L with a low drum speed and at least about 16, 8 and 4 minutes, and then a working cycle L with simultaneous activation of the discharge pump 5, and finally a spin cycle.

The pre-wash cycle (Fig. 9), which may optionally be provided, can be initiated by appropriate setting of the timer 24, and this Prewash cycle comprises a supply cycle C during which the water coming from the supply line 20 is introduced directly into the trough 2. During this first cycle or during at least a part of it, the circulation pump 9 is activated so that the water is led from the trough 2 into the basin 17, from where it exits from the nozzle 16 so that the detergent is flushed out and then the solution enters the trough 2 again. The supply cycle C is followed by a first working cycle L with a low drum speed during which the circulation pump 9 is again activated at least partially. The supply cycle C and the first working cycle L, during which automatic regulation of the water level according to the amount of laundry loaded is not possible, have a total duration of about 16 minutes. This is then followed by a second and a third working cycle L, each lasting about 2 minutes, during which the drum performs a rotating movement at a low speed. At the end, a discharge cycle S is carried out during which the discharge pump 5 is activated. In the example shown and described, there are no cycles with high speed rotation of the drum during the prewash cycle, but recirculation cycles are included. This obviously means that the quantity of water supplied during the supply cycle C must be greater in order to prevent the resistances from being exposed and cavitation of the recirculation pump 9 as a result of the water circulation. However, in the case of extremely dirty laundry, it may be convenient to have a larger quantity of water available in the tub 2 during this phase. It is however possible, as an alternative to the example shown, to have a cycle in which the drum rotates at high speed even during the prewash cycle.

The rinsing cycle comprises four phases R1-R4, which are carried out in succession. The first phase R1 comprises an initial cycle G, which lasts approximately 2 minutes and during which water is introduced into the trough, in which the drum 3 simultaneously rotates at a high speed and the circulation pump 9 is also activated. The water contained in the trough 2 is circulated by the Pump 9 partially delivers water into the basin 17, from where an additive contained in one of the containers 22 is taken (for example a conditioning agent) and this is partially injected into the trough via the spray nozzle 19. The water supply continues, the laundry gradually absorbs the required amount of water (depending on the type of laundry) until the predetermined level is reached, which is controlled by the pressure switch.

This is followed by a first working cycle L with the drum 3 rotating at low speed for about two minutes, a cycle G with the drum 3 rotating at high speed for about two minutes and simultaneous activation of the circulation pump 9 and a second working cycle L with the drum 3 rotating at low speed for about two minutes. The water is then drained while the drum rotates at low speed. A spin cycle is then carried out for about two minutes.

Phases R2 and R3 are consistent with each other and coincide with phase R1.

Phase R4 comprises an initial cycle G for the water supply with a rotation of the drum at high speed and simultaneous activation of the circulation pump 9. This initial cycle lasts approximately two minutes. This is then followed by a first working cycle L of approximately two minutes in which the drum 3 performs a rotational movement at low speed. This is followed by a second working cycle L with simultaneous activation of the outlet pump 5. Finally, two spin cycles are carried out, for which a period of time of two and four minutes is specified respectively.

Tests have shown that when using a washing tub with a normal capacity and a circulation pump with a flow rate of about 18 litres per minute, it is sufficient to fill the washing drum with a water quantity of about 12 up to 13 litres in order to obtain an optimum washing result and to ensure that during the water circulation cycles, with a rotation of the drum at a high speed of between 100 and 150 rpm, no cavitation occurs in the circulation pump and the water level in the tub does not fall below the heating elements 40. However, the same tests have also shown that under the same conditions, a rotation of the drum at a normal working speed of 50 to 60 rpm led to cavitation in the circulation pump after about one minute.

Fig. 10 shows schematically a second preferred embodiment of a washing machine in which the washing method according to the invention can also be used. A washing machine of this type is described, for example, in the above-mentioned Italian patent application No. M192A0002562. Unlike the washing machine in Fig. 1, there is provided a single pump 30 which serves both for discharge and for circulation. The pump 30 is connected to the inlet of the washing drum 2 via the line 4 and to the outlet via a line 31. Also connected to the line 31 is a flow deflector (which is designed in the form described in the Italian patent application No. 21702 A/81 of 14 May 1981), which can be seen most clearly in Fig. 11. This flow diverter essentially has a Y-shaped connection to an internal switching valve 32 (which is operated, for example, by means of an electromechanical device, not shown). This switching valve 32 can be moved between a closing position for a first outlet line 33 and a closing position for a second outlet line 34. The first outlet line 33 is connected to the outlet line 7, while the second outlet line 34 is connected to a line 35 which supplies the nozzle 16 inside the basin 17. A branch of a line 36 which supplies the spray nozzle 19 which is arranged in the central region of the drum 3 is connected to the second outlet line 34.

In the basic state, the switching valve 32 is in the closing position for the first outlet line 33, as shown in Fig. 11, so that when the pump 30 is activated, the water contained in the trough is circulated. However, when the water contained in the trough is discharged, the switching valve 32 is brought into the closing position for the second outlet line 34.

It is important that the flow deflector is arranged at a height from the bottom of the trough 2 which is sufficiently large so that when the pump 30 is deactivated, the vacuum or negative pressure generated in the line 31 causes the line 31 and the water located there to be emptied, which may also contain lint residues in the washing liquid which could possibly be returned to the pump 30.

Claims (12)

1. Washing method for a washing machine with at least one washing phase (L1-L3) comprising a high speed working cycle and a recirculation of water, during which a drum (3) containing the laundry to be washed and rotatably housed in a washing tub (2) to which fresh water has been previously supplied is caused to rotate at a first speed sufficiently high to generate a centrifugal force causing the laundry to be arranged along the periphery of the drum (3) and at the same time the water contained in the washing tub (2) is taken out of the tub (2) and reintroduced therein by spraying at a central part of the drum (3), and a subsequent low speed working cycle during which the drum (3) is caused to rotate at a second speed lower than the first speed and to allow remixing of the laundry while a recirculation of the water is substantially interrupted, characterized in that the high speed and water recirculation operating cycle has a duration limited to the time required for complete removal of a detergent from a detergent container (22), and during the high speed and water recirculation cycle, a portion of the water taken out of the trough (2) is caused to pass through the detergent container (22) and subsequently to be reintroduced into the trough (2). 2. Process according to claim 1, characterized in that the working cycle at high speed and with a return of water has a duration which is substantially equal to two minutes. 3. Method according to claim 1 or 2, characterized in that the first speed is between 100 and 150 rpm. 4. Method according to claim 1, characterized in that it provides an initial supply of a quantity of water sufficient to guarantee reaching a preset level (41, 42) of water in the trough (2), and a subsequent working cycle preceding the high speed and water return cycle, during which the drum (3) is caused to rotate at a low speed to allow the laundry to be uniformly wetted, with a simultaneous supply of a further quantity of water to automatically restore the preset level (41, 42) of water in the trough (2). 5. A method according to any one of the preceding claims, which also comprises at least a rinsing phase (R1-R4) following the washing phase (L1-L3) and which provides a high speed, water recirculation working cycle during which the drum (3) rotates at the high speed and the water is simultaneously removed from the trough (2), the water being partly caused to pass through a container (22) for a rinsing additive and then reintroduced into the trough (2), and partly being injected into the trough (2) by spraying at the central part of the drum (3). 6. Process according to claim 5, characterized in that the cycle with high speed and a return of water from the rinsing phase (R1-R4) has a duration of about 2 minutes. 7. A method according to claim 5 or 6, characterized in that it provides for a supply of water up to a preset level during the high speed working cycle and a return of water. 8. Method according to claim 5, 6 or 7, characterized in that the rinsing phase (R1-R4) comprises a further cycle of rotation of the drum (3) at the high speed and a simultaneous return of the water contained in the drum, alternating with working cycles during which the drum (3) rotates at the low speed. 9. Method according to one of the preceding claims, which also comprises a pre-wash phase which is carried out before the washing phase (L1-L3) can, characterized in that the prewash phase includes at least one cycle of recirculation during which the water contained in the trough (2) is partly caused to run into a container (22) for a prewash agent and then reintroduced into the trough (2), and partly injected into the trough (2) by spraying from the central part of the drum (3). 10. Washing machine with a washing tub (2) in which a drum (3) for loading laundry to be washed is rotatably housed, a first recirculation circuit (8-13, 15-17, 21) for removing water from the tub (2), for sending the removed water to a container (22) for detergent or an additive and for returning the removed water to the tub (2), a second recirculation circuit (8-12, 14, 18, 19) for removing water from the tub (2) and for spray-injecting the removed water into the tub (2) at a central part of the drum (3) and a recirculation pump (9, 30) connected to the tub and to the first and second recirculation circuits, characterized in that it comprises means (24) for activating the recirculation pump (9, 30) in combination with the rotation of the Drum (3) at a sufficiently high speed to generate a centrifugal force so that the laundry is arranged along the circumference of the drum (3) and for a time equal to that required to empty the container for detergent or an additive (22). 11. Machine according to claim 10, characterized in that the recirculation pump (9, 30) has a flow rate of about 18 liters per minute, the first circuit for recirculation has a flow rate of about 7-8 liters per minute and the second recirculation circuit has a flow rate of about 10-11 liters per minute. 12. Machine according to claim 10 or 11, characterized in that the recirculation pump (9, 30) also works as a discharge pump with an output which can be alternatively connected to the recirculation circuits (8-13, 15-17, 21; 8-12, 14, 18, 19) and to a discharge line (7) via a flow distributor (32) with electrical control, the flow distributor (32) being arranged at a height close to the upper end of the trough (2).