GB2346622A

GB2346622A - Clothes washing machine with counterbalanced tub

Info

Publication number: GB2346622A
Application number: GB0001560A
Authority: GB
Inventors: Roberto Quattrin; Flavio Rigo
Original assignee: Electrolux Zanussi Elettrodomestici SpA; Electrolux Zanussi SpA
Current assignee: Electrolux Zanussi Elettrodomestici SpA; Electrolux Zanussi SpA
Priority date: 1999-01-25
Filing date: 2000-01-24
Publication date: 2000-08-16
Anticipated expiration: 2020-01-24
Also published as: ITPN990011A1; ES1045316Y; FR2788790B3; GB2346622B; IT1311196B1; FR2788790A3; GB0001560D0; DE20001124U1; ES1045316U

Abstract

Clothes washing or washing-drying machine in which the washing assembly comprises a rotary drum 16 enclosed in a tub on which counterweights 30, 50 are removably fixed. For that purpose the arrangement uses fixing means comprising: expansion blocks 31-35, Fig 2, screws 36, Fig 3, and holes 41-45. The fixing means axes are disposed substantially parallel to the axis of rotation X, Fig 2 of the drum 16, along the neutral section N, Fig 2 of the washing assembly.

Description

2346622 CLOTBES WASHING MACHINE WITH COUNTERBALANCED TUB The present

invention concerns a clothes washing or washing-drying machine in which the washing assembly comprises a tub, a rotary drum and counterweights to reduce dynamic stresses.

EP-A-0 497 109 sets forth a tub of a front-loading clothes washing machine which substantially consists of two casing portions which are respectively a front casing portion and a rear casing portion and which are made from plastics material and joined together by bolts disposed parallel to the axis of rotation of the drum. A counterweight of substantially annular shape and provided with radial grooves is directly and removably fixed to the front casing portion by means of bolts which are disposed along the grooves. A second counterweight which is in the shape of a circular arc is in turn fixed to the upper part of the rear casing portion by means of bolts which are disposed in directions that are substantially orthogonal to the axis of rotation of the drum.

A first disadvantage of that structure is that the flexural and torsional stresses generated in the tub during the phases when the drum rotates at high speed are very high at the bolts for fixing the counterweights. It is thus necessary to use bolts which are made from materials involving high mechanical characteristics or to use a fairly large number of bolts if they are made from materials of lower quality. In both cases the production cost of the tub is undesirably high. A second disadvantage is that, when the counterweights have to be removed from the tub (which happens both when there is a need to replace a drum which has suffered damage during use of the machine and during dismantling of the machine at the end of its life for recycling the materials thereof), the operations to be implemented are relatively complicated and/or long and thus inevitably expensive.

Clothes washing machines are also known in which the counterweights incorporate resilient bushes - see DE-A-1 186 413 - or which use additional metal rings see FR-A-2 359 924 - for fixing the counterweights to the tub by means of bolts which extend substantially parallel to the axis of rotation of the drum. Those constructions therefore require a relatively high number of components and can thus be the cause of critical management states during mass production of the washing machines.

The aim of the present invention is to provide a clothes washing or washing-drying machine having the tub made from plastics material in which the counterweights are fixed to the tub by simple means which are not large in number and which are not expensive and which, when necessary, are also easily removable.

According to the present invention there is provided a clothes washing or washing-drying machine in which the washing assembly comprises a rotary drum enclosed in a tub on which counterweights are removably fixed by screw fixing means whose axes are disposed substantially parallel to the axis of rotation of the drum, wherein said screw fixing means are additionally located such that they are disposed along the neutral section of the washing assembly.

The expression "neutral section" is used herein in a similar sense as "neutral axis" is applied to a beam under bending in the mechanical engineering field.

More precisely, "neutral section" is intended to indicate the notional geometric surface within the body of the counterweight where no mechanical stresses are applied to the counterweight by the oscillating washing unit of the machine. Practically speaking, the neutral section is coincident with the geometrical envelope of the various centres of gravity of laminar cross sections of the counterweight perpendicular to the axis around which the oscillations cause bending forces in the counterweight.

The location of the neutral section can either be calculated by means of simulation methods of CAE (Computer Assisted Engineering) and/or plotted experimentally by suspending the body in several configurations in order to determine said centres of gravity.

The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which:

Figure 1 is a view in suitably simplified form of a front-loading clothes washing machine shown in phantom in an exploded condition, Figure 2 is a view from the front of a part of the external casing and the washing assembly of the Figure 1 machine, Figure 3 is a partial section taken along line IU-M in Figure 2 on an enlarged scale, and Figure 4 is a view from the front of a counterweight suitable for being fixed to the front casing portion of the washing assembly shown in Figure 2.

The external sheet metal casing I of the clothes washing machine shown in Figures I and 2 comprises: a front wall 2 having a circular opening 3 which is closable I by a porthole door 4, and a subjacent control panel 5; side walls 6, 7, a rear wall 8 and a structural base portion 9, as well as an upper worktop (not shown).

The washing assembly in turn comprises:

- a tub formed by a front casing portion 10 and a rear casing portion 11 (shown only in Figure 1), each of which is produced from an in ectionmolded plastics material; - a drum 16 enclosed between the casing portions 10, 11 of the tub and rotating about a more or less horizontal axis X; and - at least a front counterweight 30 of substantially annular shape and a rear counterweight 50 in the approximate shape of a circular arc. The materials and the procedures for producing the counterweights 30, 50 are irrelevant. The casing portions and 11 are joined together by a plurality of bolts (not shown) which extend parallel to the axis of rotation X of the drum in the respective circumferential lines of holes 17, 18.

As shown in Figure 2 the front casing portion 10 comprises, in one piece:

- the above-mentioned line of holes 17; - an axially outward wall 19 with a circular aperture 20 capable of being coupled to the front opening 3 of the machine by means of a bellows seal (not shown); - the anchorage points 22, 23 for springs 12, 13 for suspending the washing assembly to the side walls 6, 7 of the casing 1; - the anchorage points 24, 25 for anchoring the washing assembly to the dampers 14, 15 with which the washing assembly is connected to the base portion 9 of the casing 1; and - the suspension points 26, 27 for suspending the actuating motor (not shown) for driving the drum 16.

In accordance with a first feature of the invention for fixing the annular counterweight 30 to the washing assembly a plurality of expansion blocks indicated by reference numerals 31 to 35 are also produced integrally in one piece with the axially outward wall 19 of the front casing portion 10 of the tub.

Figure 3 shows by way of example a view in longitudinal section of the block 32 together with a screw 36 capable of co-operating therewith as well as with one of the through holes provided on the counterweight 30 and indicated in Figure 4 by reference numerals 41 to 45, more specifically with the hole 42. In accordance with another feature of the invention the means for fixing the counterweight 30, that is to say the expansion blocks 31-35 provided integrally on the front casing portion 10 of the tub, the screws such as 36 and the holes 41-45 extend parallel to the axis X of rotation of the drum 16.

In addition, in accordance with a further and fundamental feature of the invention, for final fixing, the axes of the above-mentioned means for fixing the counterweight 30 are disposed along the neutral section N of the washing assembly. Having regard to the fairly complex shape of the counterweight 30, the fixing means (for example the holes 41-45 shown in Figure 4) are thus disposed at varying radial distances from the axis X of rotation of the drum 16 (which are indicated by references D I to D5 in Figure 4) and at varying circumferential distances from each other (which are indicated by references Ll to L5).

As regards the other counterweights, like that indicated in Figure I by reference numeral 50, in a preferred embodiment of the invention it is provided that they are fixed to the washing assembly in the same manner as described hereinbefore in relation to the front counterweight 30. In other words, a plurality of expansion blocks identical to those described hereinbefore are provided integrally in one piece with the rear casing portion 11 of the tub of the washing assembly and are co-operable both with screws as at 36 and with through holes provided on the counterweights. Consequently, the means for fixing the counterweight 50, which are identical to those described hereinbefore, are also disposed along the neutral axis of the washing assembly and substantially parallel to the axis X of rotation of the drum 16.

The advantages afforded by the present invention are thus as follows:

1. From the moment that the means for fixing the counterweights 30, 50 extend along the neutral section N of the washing assembly, they are scarcely loaded by the forces which act on the washing assembly, in particular during the high-speed spin phases, and thus it is possible to adopt a material involving lower levels of mechanical characteristics for production of the screws such as at 36 and/or to reduce the number thereof with respect to the designs which are currently in use.

2. The number of components in the machine is reduced by virtue of the fact that the expansion blocks 31-35 which form part of the means for fixing the counterweights 30, 50 are produced integrally with the two casing portions 10, 11 which form the tub.

3. The operations for fixing and removing the counterweights 30, 50 respectively can be effected in a particularly simple and rational manner since the bolts forming part of the means for fixing the counterweights are disposed in a single direction, that is to say substantially parallel to the axis of rotation X of the dnun 16.

Finally it should be noted that, when the counterweights 30, 50 are produced from a cement material or the like which has poor mechanical characteristics (except for compression strength), bushes or ferrules, preferably of metal, are interposed between the expansion blocks 31-35 and the associated holes 4145. It will be appreciated that the invention can be applied to counterweights produced from any material and/or with any production technology.

Even if the description set out hereinbefore refers to a tub made from plastics material, the arrangement of the means for fixing the counterweights along neutral axes of the washing assembly is a feature which is also suitable for tubs produced from other materials, for example stainless steel, and also for top-loading machines.

Claims

A clothes washing or washing-drying machine in which the washing assembly comprises a rotary drum enclosed in a tub on which counterweights are removably fixed by screw fixing means whose axes are disposed substantially parallel to the axis of rotation of the drum, wherein said screw fixing means are additionally located such that they are disposed along the neutral section of the washing assembly.
2. A machine according to claim I wherein said screw fixing means are disposed on the tub at varying radial distances from the axis of rotation of the drum and at varying circumferential distances from each other.
3. A machine according to claim 1 or claim 2 wherein said means for fixing the counterweights comprise screws co-operating with expansion blocks inserted in associated holes provided in the thickness of the counterweights and said expansion blocks are integrally provided in one piece with at least one of the casing portions which are made from plastics material and which form the tub of the washing assembly.
4. A machine according to any one of the preceding claims wherein at least a first counterweight is of substantially annular shape and/or that at least a second counterweight is of an approximately arcuate shape.
5. A machine according to claim 3 or claim 4 wherein, when the counterweights are made from a cement material, bushes, preferably made from metal, are interposed between the expansion blocks and the associated holes.
6. A machine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
7. A method of manufacturing a machine according to any one of the preceding claims comprising determining the location of said neutral section of such a machine and installing said screw fixing means at locations in accordance with the result of that determination.