GB2054907A - Device for controlling the water level in a tub of a laundry washing machine - Google Patents

Abstract

A device for filling a laundry- washer tub to a desired level comprises a timer 22 which measures the time taken to fill the tub to a reference level under control of an actuator 21, the timer starting when the start signal is given at 30 (also energising water entry valve 12), and finishing when the reference level is sensed by pressure-stat 20. The counter 22 delivers the time signal to a multiplier (23) wherein the signal is multiplied by a coefficient in a coefficient-setting device (40). The result is set in a timer (24), which closes the valve 12 after timing out. The filling time is thereby compensated for changes in water pressure etc. <IMAGE>

Description

SPECIFICATION Device for checking and adjusting the water level in a tub of a laundry washing machine This invention relates to a device adapted to check and adjust the level of a fluid, more particularly for checking and adjusting the water level in tubs of laundry washing machines.

In laundry washing machines it is a practical advantage to use different volumes of water, to be fed to the washing tub of the machine, as a function of the different washing modes. The washing mode is expressed, for example, by the different stages of washing programme, such as prewashing, washing proper, rinsing, and the like, and also the weight of the laundry and its degree of soiling.To solve the problem outlined above, there can be used devices which essentially comprise a duct for feeding to the washing tub, water, the flow of which can be cut off by an adjusting electromagnetic valve of the ON-OFF type controlled by a number of pressure-stats, said duct communicating with the bottom of the tub, The number of the pressure-stats corresponds to the number of desired water levels and the pressure-stats coact with a programmer which enables a certain pressure-stat, calibrated for the level concerned, to drive the electromagnetic valve. This approach has several defects. It requires a high number of pressure-stats in the case in which a considerable number of levels is desired, or, as an alternative, an intricate and sensitive pressure-stat which is sensitive to a number of levels.

If water levels are desired, which are only slightly different in magnitude from each other, it is imperative to adopt precision pressure-stats which are very expensive and prone to failure, so that their reliability is questionable.

Another approach, which dispenses with the use of pressure-stats, consists in energizing the electro-magnetic valve for a preselected time: the valve, in this case, is directly driven by the programming device for a time which varies as a function of the desired level, and thus of the desired water volume.

Also this approach is not exempt from shortcomings. As a matter of fact, the rate of flow of water coming from a water main may vary from an area to another, and also within a daily span, due to the pressure variations in the municipal network on account of the structure of the network and the variability of the water demand by the other numerous network users. As a result, a timed water feed which does not take such rate of flow variations into appropriate account, can be conducive to an inaccurate metering of the washing water to be fed to the machine tub. A trade-off approach in which the combined use of pressure-stats and timers is adopted, may be such as to sum the above outlined drawbacks together.

An object of the present invention is to offset the defects indicated above by providing a device for adjusting the volume of the water to be fed to a laundry-washer tub in order that the accurate regulation of the different levels in the tub may be achieved.

To this purpose, the invention provides a device for controlling the volume of the water to be fed to a laundry-washer tub, said device being characterized in that it consists of a duct for feeding water to a washing tub, said duct being cut off by an electromagnetic valve, means for counting the reference time of electromagneticvalve opening which is required for reaching a reference level of liquid in the tub, means for multiplying such reference time by a coefficient which is so selected as to have a filling time magnitude value to be transferred to a timer, the latter then sending to the electromagnetic valve an opening electric signal for the duration of the calculated filling time.

The single FIGURE of the accompanying drawings shows a block diagram which has the only purpose of illustrating the elementary functions required for the device of the invention.

At 10 a tub is shown, which receives water from a duct, 11, connected to a water main or any other source of pressurized water and cut off by an electromagnetic valve 12 of the ON-OFF type, valve 12 being normally closed.

At 20, a pressure-stat is shown which is capable of delivering a signal as the water level in the tub 10 has attained a preselected reference value, to send said signal to a cycle-starting actuator 21, which drives a clock 22. The clock 22, in its turn, delivers a signal as a function of the time which has been counted, to a multiplier 23 which delivers the signal, multiplied by an appropriate coefficient (preset at 40) to a timer 24.

The signals delivered by the timer 24 and the actuator 21 are sent, amplified at 25, to the electromagnetic valve 12.

The operation of the circuitry is thus as follows: A filling-start signal, delivered at 30, drives the cycle-starting unit 21: the latter drives the electromagnetic valve 12 to open and maintains it open while simultaneously energizing the clock 22. As soon as the pressure-stat 20 is energized by the attainment of the reference level, it delivers a deactuating signal to the unit 21, which cuts off the delivery of signals to the electromagnetic valve 12 and stops simultaneously the clock 22: the latters sends a signal corresponding to the counted up time (for having the reference level attained in the tub) to the multiplier 23: here the time signal is multiplied by the coefficient which has been set at 40.The multiplied signal is delivered to the timer 24 so that the latter is actuated for a time which is a function of the time required for attaining the reference level: the electromagnetic valve 12 is meanwhile kept open and the tub 10 receives a water volume which can be determined by the setting at 40 of the value of the multiplying coefficient.

It is apparent from the foregoing description that the type of control of the tub filling is of the timer-class, but the time constant in function of which the filling volume is evaluated is not fixed once for all, but is calculated from time to time at the cycle start. Thus, the unacceptable defect is offset of having the water volume to be fed to the tub a function of the pressure obtaining in the water main the more so that the relationship -binding the fluid rate of flow in a hydraulic circuit of the kind usual for feeding a laundry washer to the pressure in the main are well known.

As a matter of fact, according to the invention, not only the differences existing between the pressures in the several areas of the water municipal network are allowed for, but also the instantaneous pressure variations occurring during a daily span are satisfactorily balanced.

As aforesaid, the circuitry shown in the drawings, is indicative of the several basic functions necessary for the operability of the device according to the invention as diagrammatically shown to give to those skilled in the art all the indications which are necessary for reducing the invention to constructive practice.

The individual circuit sub-assemblies required for fulfilling each and every function are well known to the technicians of processing and control systems so that such individual sub-assemblies have not been described in detail.

Generally speaking, in the practical commercial embodiments of the invention, the several components which are required for making up an operable system will be combined, with advantage, into a micro-processor which receives the pressure-stat signals and which drives the feeding electromagnetic valve via a power interface, whereas any necessary data are set by an external interface of such microprocessor.

The multiplication coefficient for the reference time (filling time) can be given by the microprocessor automatically, during the progress of the several washing stages, when the microprocessor is also in a position, as now usual in the art, to command the several operational stages of the laundry washer in the correct sequential order, that is, to deliver automatically and at the proper instants of time, the command of water inlet to the washing tub.

Things can be arranged so that this command corresponds always to the manual control 30, or, alternatively, that only the first filling step may be so commanded, whereas the subsequent filling stages may require the mere actuation of the timer for the time set, from time to time, at 40 by preselecting each time the multiplication coefficient consistently with the filling requirements individually. Stated another way, the time for filling the tub up to the reference level, stored at 22, may be taken as the time constant which is counted up at every filling step, or can it be counted up on the occasion of the first filling only for each washing cycle, the latter comprising a sequential succession of more filling steps within a comparatively short time interval.

The reference level to be used for counting the time constant is not critical, said time constant being the basis for reaching the several levels to be used: it is only required that such reference level is not higher than the level which is desired for the filling step wherein the time constant is counted.

In the most general case in which the crosssectional area of the tub is not wide, such as in the horizontal-axis cylindrical tubs, slight volumes of water as introduced, cause substantial level variations, so that the pressure-stat takes at any rate a high sensitivity, that which corresponds to an accurate measurement of the reference level.

As aforesaid, a number of variations in the practical embodiments can be envisaged to achieve the objects of this invention, while remaining within the scope thereof.

Claims (4)

1. A device for checking and adjusting the volume of water fed to a washing tub of a laundry washer, characterized in that it comprises a duct for feeding water to the tub, said duct being cut off by an electromagnetic valve, means for counting the reference time of opening of the electromagnetic valve which is necessary for attaining a liquid reference level in said tub, means for multiplying the reference time by a coefficient to be set for obtaining a filling time value and to transfer same to a timer adapted to deliver an electric opening signal to said valve during the calculated filling time.

2. A device according to Claim 1, characterized in that said means for counting the reference time comprise a pressure-stat sensitive to the attainment in the tub of said reference level and a storage counter timer for the time of opening of the electromagnetic valve as is necessary for attaining in said tub the level sensed by the pressure-stat.

3. A device for controlling the water level in a laundry washer tub so as to attain a predetermined water level at a predetermined instant of time, characterized by comprising a pressure-stat (20) delivering a signal as the water level has attained a reference valve, said signals being sent to a cycle start actuator (21) driving a time counter (22), the latter delivering a signal as a function of the counted up time to a multiplier (23) wherefrom the thusly multiplied signal is sent, multiplied by a multiplication coefficient set in a coefficient-setting device (40), to a timer (24), the signals delivered by the timer (24) and by the actuator (21) being amplified in an amplifier (25) and delivered to the electromagnetic valve (12) to control the water feed to the tub (10), the cycle start actuator being manually commanded by a manual commanding device (30).

4. A device according to the preceding claims, substantially as hereinbefore described and illustrated in the accompanying drawing.