EP0629733B1

EP0629733B1 - Machine for washing and rinsing fabrics

Info

Publication number: EP0629733B1
Application number: EP94106434A
Authority: EP
Inventors: Piero Babuin; Silvano Cimetta
Original assignee: Electrolux Zanussi Elettrodomestici SpA
Current assignee: Electrolux Zanussi Elettrodomestici SpA
Priority date: 1993-06-18
Filing date: 1994-04-25
Publication date: 1997-01-02
Anticipated expiration: 2014-04-25
Also published as: EP0629733A1; ITPN930042A1; DE69401309D1; DE69401309T2; ES2096966T3; ITPN930042A0; IT1268525B1

Description

The present invention relates to a machine for washing and rinsing fabrics, in particular to a household machine for washing and rinsing fabrics, according to the preamble of claim 1.
In the following there will be specific reference to household washing machines, but it is understood that the present invention is entirely applicable to machines for washing and drying fabrics as well.
Washing machines, particularly household washing machines, are known that utilize electromechanical means called programmers for making the functional elements of the machine perform all the required functions, with the times and in the sequence desired.
The current drive on the market to reduce all kinds of consumption, from energy to raw materials to the water for household use, together with the constant endeavor to orient service increasingly toward the consumer's needs, has stimulated the development and production of increasingly efficient washing machines with reduced consumption of energy, detergent and/or water.
So-called recirculating washing machines have therefore been particularly developed in recent years, which all offer very reduced water consumption.
Since the greatest water consumption occurs during the conventional rinsing phases, the effort to reduce water consumption has unfortunately been concentrated on reducing water consumption during these rinsing cycles, the inevitable consequence being a progressive lowering of the water level in the tank to the point that it merely touches the lower edge of the drum so that the laundry contained there is not sufficiently soaked; this is all the more so when there is a full laundry load in the drum.
The logical consequence has been an inevitable impairment of rinsing results, whether in conventional machines or in ones functioning with recirculation of washing liquid.
Technical solutions have naturally been developed for eliminating the disadvantage of unsatisfactory rinsing. For example, DE 4 115 776 C2 illustrates a rinsing process consisting in a succession of centrifuge impulses alternating with water loading phases.
Nevertheless the proposed solution is not fully satisfactory because of the considerable frequency with which water is drawn into the tank and the resulting elevated use of the pressure switch.
The document US-A-3,388,410 discloses a cleaning apparatus and a method for cleaning clothes wherein the drum is rotated at two different speeds during the cleaning cycle. In addition, the rotary chamber speed is increased during the washing phase only, which means that the intention is to increase the cleaning action and not to reduce the amount of water consumption during the rinsing phase.
The document DE-A-40 13 450 discloses a method for washing and cleaning wherein the drum is rotated at various speeds during the rinsing phase. These different rotations or speed phases have not a prescribed order. Moreover, the recirculating pump is not kept in operation during the drum rotation phase during the rinsing cycle.
The patent application FR-A-2 632 983 teaches a washing machine which has neither the water recirculation means nor a second high speed period being placed between a first period and a third period both of them at low speed.
It is, therefore, the object of the present invention to realize a machine for washing and rinsing fabrics, in particular a household washing machine, that combines the advantages of low water consumption with a satisfactory rinsing performance typical of conventional machines that have elevated water consumption.
Furthermore this object should be reached with no need for major modifications of the machine, without significantly increasing the production cost or the circuit complexity of the washing machine, and without impairing its reliability.
This object is achieved by a machine for washing and rinsing machine for washing and rinsing fabrics, in particular a household washing machine, equipped with a particular mode of operation during rinsing, as described in claim 1.
The machine for washing and rinsing fabrics according to the invention is equipped with a particular electric circuit which, associated with a specific type of timer, permits several rinsing cycles in order to improve the rinsing performance without increasing the water consumption.
The invention will be understood better from the following description, intended solely as a nonrestrictive example, with reference to the adjoined drawing in which the single figure shows in simplified fashion the characteristics of a rinsing cycle according to the invention.
The devised solution essentially consists in the performance of at least one rinsing cycle effected in such a way that all the water available in the tank, even if in reduced amount, is circulated several times in forced fashion through all the laundry, which improves the laundry-water exchange and maximizes the capacity of the rinsing water to remove the suds impregnating the fabrics.
This is obtained, in brief, by effecting one or more short periods, or impulses, of drum rotation at high speed during the rinsing cycle, in such a way that all the reduced amount of water available is made to pass through the fabrics several times, thereby maximizing the effect of removing the suds therefrom.
To obtain this result the rinsing cycle is composed of three distinct phases: the first phase A, in which rinsing water is loaded into the washing and rinsing tank, the second phase B in which the actual rinsing of the laundry contained in the drum is performed, and finally the third phase C in which the water employed for rinsing is discharged from the tank, to make room for any successive rinsing cycles or to activate other functions, for example initiate a final centrifuging or drying cycle, or to stop operation of the machine definitively.
The present invention relates in particular to the second phase B illustrated above; in this phase the rinsing occurs in three periods, a first period B1 in which the drum turns at low speed to enable all the laundry to be soaked by the water admitted into the tank.
In order to improve the laundry-water exchange, the drum is turned in this first period B1 at a normally low speed, which can be constant or can vary between several speeds, the lower speed permitting the laundry to crowd together on the bottom of the drum, and the higher speed permitting at least part of the laundry to spread out along the inside cylinder of the drum due to the centrifugal force.
This higher speed need not necessarily be the minimum speed at which all the laundry spreads out along the drum, but is the speed at which the laundry opens up and thus at least part of it comes in contact with the inside perimeter of the drum, while the remaining part is simply opened up in the central space of the drum. However, this terminology and the desired effects are well known to the expert in the field and will therefore not be dwelt on further.
After first period B1, which can typically last 2 to 3 minutes, second period B2 begins which is characterized by providing a short impulse of high rotating speed to the drum. The purpose of this period is twofold: to complete the exchange between all the laundry and the available water, and to free the laundry as much as possible from water which is thus made fully available for other successive phases.
It has been found that optimal values in phase B2 are a minimal time of 3 seconds at the final centrifuging speed of the machine, or a rotating speed corresponding to a centrifugal acceleration of at least 10 g, in accordance with the cylindrical band of the drum, for at least 3 seconds.
At the end of period B2 the third period B3 is carried out, consisting in a further low speed rotation of the drum in order to enable the laundry to be detached from the inside wall of the drum against which it was driven by the centrifugal force and to fall to the bottom of the rotating drum to be soaked in the water contained there.
The features of this period B3 are entirely similar to those of period B1, and will therefore not be repeated.
At this point one rinsing phase can be considered concluded but, to improve the rinsing efficiency, it is expedient to repeat periods B1, B2 and B3 in the indicated order a certain number of times, if only to obtain the greatest rinsing effect in line with the initial concentration of suds and the amount of fresh water loaded for this rinsing.
An advantageous variant of the solution indicated above can be obtained by rotating the drum at a low speed sufficient for making at least part of the laundry spread out along the cylindrical band of the drum. In this way there is a lower height of laundry on the bottom of the drum and the laundry will therefore be penetrated better by the water since it will be more immersed in the water contained in the tank and, because of its limited amount, will reach a modest level with respect to the bottom of the drum.
This innovation is particularly advantageous if the washing machine functions by the mode known as recirculation of liquid in the tank.
If the recirculation is effected in these machines by withdrawing the liquid from the bottom of the tank and readmitting it through a nozzle disposed in such a way that its jet points toward the center of the drum, the performance obtainable with the above-described solutions is enormously enhanced. When the jet hits the laundry disposed against the cylindrical band of the drum it soaks all the laundry from the inside, and the centrifugal force due to the fairly fast rotation of the drum, which naturally also acts on the liquid as soon as it is sprayed, drives it toward the outside making it pass through practically all the laundry and therefore increasing the exchange between residual suds within the laundry and rinsing liquid.
A further advantage of the invention will now be clear, consisting in the fact that the washing machine is not very complicated; in fact the invention can be realized merely by connecting an expedient programmer with no other modification of the machine. In fact, because the machine according to the invention is characterized solely by a particular mode of operation of the programmer, the present invention can be easily employed in machines already in service at the consumer's by merely replacing the programmer.
Obviously, any washing machine that functions in accordance with the following claims, even if realized with different forms and arrangements, falls within the scope of protection of the present invention.

Claims

A machine for washing and rinsing laundy, comprising a washing tank, a drum inside the tank for receiving the fabrics to be washed and rinsed, a programmer, the electric circuits connecting the programmer to the various functional elements of the machine, a circuit for recirculating the liquid contained in the tank, a recirculating pump inserted in the circuit, a discharge nozzle of the circuit disposed with an orientation so as to cast the liquid jet into the central inside area of the drum, and at least one rinsing cycle that includes a phase (A) for loading rinsing liquid into the tank, a drum rotation phase and a phase for draining the rinsing liquid, characterized in that the drum rotation phase is composed of a first period (B1) in which the drum rotates at low speed, a second period (B2) in which the drum is brought to a rotating speed similar to the centrifuging speed with a short impuls of high rotating speed, and a third period (B3) in which the drum is slowed down to a low rotating speed and during the phase for loading rinsing water the drum is rotated at a speed sufficiently high to distribute at least part of the laundry along the inside cylindrical perimeter of the drum and the recirculating pump is kept in operation during the drum rotation phase during the rinsing cycle.
The washing machine according to claim 1 characterized in that the second period, in which the rotating speed is similar to the centrifuge speed, lasts between 3 and 30 seconds, and
in the second period the rotating speed is such as to impart, in accordance with the cylindrical perimeter of the drum, a centrifugal acceleration of at least 10 g for at least 3 seconds.
The washing machine according to any of the previous claims, characterized in that the rotating speed of the third period (B3) is sufficiently high to distribute the laundry along the inside circular perimeter of the drum.