EP1264925A2

EP1264925A2 - Washing machine with weight sensor

Info

Publication number: EP1264925A2
Application number: EP02011152A
Authority: EP
Inventors: Giuseppe Frucco; Giovanni Colombera
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2001-06-08
Filing date: 2002-05-21
Publication date: 2002-12-11
Also published as: EP1264925A3; ITPN20010041A1

Abstract

The washing machine comprises a sensor (8) adapted to detect the displacement of the oscillating assembly (2) and arranged between a vibration-damping strut (3) of said oscillating assembly and the framework (5) of the machine, upstream of the support feet thereof, so as to be able to sense the variations in the weight of the oscillating assembly in a manner that is independent of the braking force of the vibration-damping strut (3) and the weight of the machine.

Description

The present invention refers to a washing machine, such as a clothes washing machine or a combined clothes washing and drying machine, provided with means adapted to measure the weight of the clothes loaded in a washing assembly that is suspended elastically to the framework of the machine with the aid of spring means such as vibration dampers or the like.
From the disclosure in DE-A-1992087 the solution is known, which consists in providing, in correspondence of at least a vibration-damping strut supporting the washing tub, a displacement sensor that comprising a pumping device adapted to generate a pressure that depends on the displacements of the washing tub and is converted, through an analogue pressure switch, into a signal representing the weight of the entire washing assembly. Such a weight signal can then be processed to measure, i.e. find out the weight of the clothes.
On the other hand, with this solution the above mentioned pressure is affected by the damping effect of the vibration-damping strut, which practically means that the actuations of the pumping device are determined not only by the weight of the clothes and the washing tub, but also by the braking force of the vibration-damping strut. It therefore ensues that such a solution proves quite inaccurate and scarcely responsive.
A similar solution, which anyway has the same drawbacks as the afore described one, is disclosed in US-A-2 412 270, in which there is provided the use of a displacement sensor of an inductive type, rather than a pneumatic one, in correspondence of a vibration-damping strut.
The above cited drawbacks can be done away with in the manner that is for instance described in DE-A-2034847, i.e. through the provision of a load cell in correspondence of at least one of the resting feet of a washing machine. Load cells are however largely known to be quite critical, expensive and unreliable weight sensors.
In addition, with such a solution the load cell, which is in fact arranged between the base of the machine and the floor, tends to measure the overall weight of the machine, including the weight of items that may possibly be placed or resting on the worktop of the same machine, so that the whole measurement system proves quite difficult to calibrate and rate and, anyway, weight measurements are quite likely to prove substantially inaccurate.
It therefore is a purpose of the present invention to provide a washing machine equipped with a weight sensor, in which the typical drawbacks encountered in the prior art are minimized
In particular, it is a purpose of the present invention to provide a washing machine of the above specified kind, which is adapted to measure the weight of the clothes, i.e. the washload, to a high level of sensitivity and responsiveness, in a substantially accurate and reliable manner.
According to the present invention, these and further aims are reached in a washing machine with a weight sensor embodying the features and characteristics as defined and recited in the appended claims.
Features and advantages of the present invention may anyway be more readily understood from the description that is given below by way of nonlimiting example with reference to the accompanying drawings, in which

Figure 1 is a schematic view of a washing machine according to the present invention;
Figure 2 is an enlarged view of a detail of the weight sensor of the washing machine, according to a preferred embodiment thereof;
Figure 3 is a diagrammatical view of the characteristic elongation or displacement curve of one of the component parts of the weight sensor illustrated in Figure 2; and
Figure 4 is a view of a variant of the weight sensor shown in Figure 2.

With particular reference to the above mentioned Figures 1 to 3, the washing machine is for example a clothes washing machine, or a combined clothes washing and drying machine, comprising an outer casing 1 that houses an oscillating washing assembly 2 which is elastically suspended to the framework of the washing machine by means of vibration-damping struts 3 and, possibly, also by means of springs 4. The springs 4 may alternatively be incorporated directly into the vibration-damping struts 3, in a substantially per sé known manner.
The framework of the washing machine comprises in particular a base 5 that rests on the floor by means of support feet 6, preferably of the height-adjustable type.
The washing machine is provided with a programme sequence control unit 7, which may for instance comprise a microprocessor of the Motorola 6805 family, adapted to determine the operation of the operational parts and members of the machine and, in particular, to measure the weight of the clothes loaded in the washing, i.e. oscillating assembly 2 in accordance with a driving signal it receives from at least a displacement sensor 8 that shall be described in greater detail further on.
Such a displacement sensor 8 is provided in association with at least one of the vibration-damping struts 3 and in particular, according to an aspect of the present invention, it is arranged between the vibration-damping strut 3 and the base 5 (or, anyway, the framework of the machine), upstream of support feet 6.
As a result, since the sensor 8 is located downstream of the vibration-damping strut 3, it is capable of detecting the displacements of the oscillating assembly 2 (in a substantially vertical direction) in a manner that is independent of the braking action introduced by the vibration-damping strut itself. In other words, the sensor 8 is advantageously driven directly by the variations in the weight of the oscillating assembly 2 deriving from the clothes being loaded for washing in the oscillating assembly itself.
In addition, since the sensor 8 is situated upstream of the support feet 6, its operation is not dependent on the overall weight of the washing machine and, furthermore, it is not affected by the weight of foreign items that may possibly be resting for instance on the worktop 9 of the washing machine.
The displacement sensor 8 may be embodied in a manner as illustrated in Figure 2, with an appropriately shaped linking member 10 that is adapted to move in a substantially vertical direction with respect to the base 5 of the machine.
In particular, the member 10 comprises a receptacle 11 capable of accommodating a corresponding end portion 12 of the vibration-damping strut 3, and it is preferably hinged at 13, in correspondence of an end portion thereof, on to a base member 14 attached to the base 5 of the machine in a removable manner, eg. by means of screws 15.
Between the moving member 10 and the stationary member 14 of the displacement sensor 8 there is arranged a transducer 16, for instance of an inductive type comprising a coil 17 and a core 18, which are connected to the stationary member 14 and the movable member 10, respectively.
In a per sé known manner, the transducer 16 drives the programme sequence control unit 7, via a connection 19, with a signal that is representative of the displacements of the oscillating assembly 2 in a substantially vertical direction with respect to the framework of the machine.
In turn, the programme sequence control unit 7 is adapted to process such a signal in such a manner as to measure the weight of the clothes having been loaded in the oscillating assembly for washing. As those skilled in the art will be capable of readily understand, such an operation is particularly easy, accurate and reliable to carry out, since all it takes for the actual weight of the clothes, i.e. the washload, to be calculated is to subtract the (well known) tare from the overall weight of the oscillating assembly 2, the displacements of which are influenced exactly by the weight of the clothes to be measured.
According to an important aspect of the present invention, this weight measurement can advantageously be made still more accurate and simple if the moving member 10 is biased by upwards pushing elastic means, such as for instance a compression spring 20, having a substantially linear elastic deformation characteristic, as shown by way of example in Figure 3, at least within the normal working range of the spring 20. In the example of Figure 3, such a working range is indicated with the letter A and includes variations in the weight of the oscillating assembly 2 (in the case that there are provided two vibration-damping struts 3) ranging from 50/2 and 60/2 kg.
As a result, the measurement of the weight of the clothes loaded for washing turns out as being easily and readily repeatable over the time in an accurate manner, even by using a simple, low-cost processing of the signals generated by the transducer 16.
The spring 20, which is arranged between the moving member 10 and the base or stationary member 14 in the example being described, also contributes to damping the vibrations of the oscillating assembly 2 thereabove. Furthermore, there is preferably provided an elastic abuttal limit-stop piece of rubber 21 adapted to prevent the transducer 16 from being exposed to mechanical shocks in the event of particularly marked oscillations, i.e. displacements of the oscillating assembly 2, such as they may for instance occur in spin-extraction phases of washing cycles.
In this connection, those skilled in the art will be capable of readily understanding that the signal that drives the programme sequence control unit 7 can also be used to measure off-balance states of the oscillating assembly 2 during spin-extraction phases of the washing cycle.
In all cases, the entire displacement sensor 8 can be advantageously implemented as an integrated component part (comprising mainly the moving member 10, the spring 20 and the transducer 16) that can be tested and calibrated separately, i.e. off-line, before being actually assembled in position between the vibration-damping strut 3 and the base 5 of the machine.
Analogous considerations apply also to the variant illustrated in Figure 4, where the inductive transducer 16 is replaced by a sensor of a pneumatic type.
In particular, between the moving member 10 and the base 5 of the machine there is arranged a pneumatic capsule or cell 22 connected to an input 23 of an analogue pressure switch 24, or the like, adapted to drive the programme sequence control unit of the machine with signals that correspond to the pressure generated by said pneumatic cell 22 in response to and in accordance with the displacements of the moving member 10.
In a preferred manner, the pneumatic capsule 22 is provided with a vent 25 equipped with a normally closed controlled valve 26. This valve 26 can be opened during spin-extraction phases so as to enable the capsule 22 to be freely deformed, thereby preventing it from breaking down, in response to the usually strong mechanical stresses imparted to the moving member 10 by the oscillating assembly 2.
It will be appreciated that the above described washing machine may be the subject of a number of modifications without departing from the scope of the present invention.
For example, instead of being hinged at 13, the moving member 10 may be fastened to the base member 14 in a different manner, via one or several springs 20. Furthermore, the spring 20 can be of the pulling type, instead of a compression or pushing one.
In any case, it can be readily and clearly appreciated that the washing machine according to the present invention is by all means capable of performing an accurate measurement of the weight of the clothes to be washed by using, rather than a delicate weight sensor, a displacement sensor which is particularly simple, reliable and capable of withstanding even the quite strong mechanical stresses that are usually imposed during spin-extraction phases of the washing cycles performed by the machine.

Claims

Washing machine comprising an outer casing provided with support feet (6) and housing an oscillating washing assembly (2) suspended elastically to the framework of the machine via at least a vibration-damping strut (3), in which the washing machine also comprises at least a sensor (8) detecting the displacement of said oscillating assembly, characterized in that said displacement sensor (8) is arranged between said vibration-damping strut (3) and the framework (5) of the machine, upstream of the support feet (6) thereof, so as to be able to sense the variations in the weight of the oscillating assembly (2) in a manner that is independent of the braking force of the vibration-damping strut (3) and the weight of the machine.
Washing machine according to claim 1, characterized in that said displacement sensor (8) comprises a member (10) capable of moving in a substantially vertical direction with respect to the framework (5), to which it is connected via elastic upwards pushing means (20).
Washing machine according to claim 2, characterized in that said elastic means (20) have a substantially linear elastic deformation characteristic.
Washing machine according to claim 2, characterized in that said displacement sensor (8) is implemented as a separate, self-contained component part, comprising said moving member (10), said elastic means (20) and said transducer means (16; 22), and capable of being assembled in position in a removable manner.
Washing machine according to claim 2, characterized in that between said moving member (10) and the framework (5) of the machine there are provided elastic abutting limit-stop means (21).
Washing machine according to claim 2, characterized in that said moving member (10) of the displacement sensor (8) is adapted to drive transducer means (16; 22) which in turn drive the programme sequence control unit (7) of the machine with signals that are indicative of the variations in the weight of said oscillating assembly (2).
Washing machine according to claim 6, characterized in that said transducer means comprise a pneumatic capsule or cell (22) adapted to drive the programme sequence control unit (7) of the machine via an analogue pressure switch (24), in which said capsule (22) comprises a vent (25) provided with normally closed valve means (26) that are capable of being opened during pre-determined phases of the washing cycle.