TUB FOR WASHING MACHINE

FIELD OF APPLICATION OF THE INVENTION

This invention, as expressed in the title of this specification, relates to a plastic tub for a clothes-washing machine, in particular of the domestic type which houses a rotating drum, inside which the washing load is placed; said washing tub consisting of a peripheral, cylindrical housing formed by a tub front-section and a tub rear-section which are joined in order to enclose the drum in its interior by means of plastic fusion welding, and where the front section of the tub features at least one front lug, and the rear section of the tub features at least one rear lug which face each other on closing the tub, and to which a damper is affixed by means of a pin.

BACKGROUND OF THE INVENTION

The majority of the tubs existing on the domestic washing-machine market with moulded plastic washing tubs are joined by means of assembly with clips and/or screws. The joint is carried out by joining, by means of clips, the front section of the tub with the rear section of the tub, which incorporates the internal features, already assembled, such as the drum, the shaft, etc.

The joining of tubs by means of welding is not new on the market. Among the different welding techniques existing, the most commonly used is welding by vibration. Said vibration may be produced by means of ultrasonics or by friction, and the melting of the material at the joint is based on the application of pressure in order to produce close contact between the items to be welded. In comparison with the solution of tubs joined by means of clips, welded tubs allow the elimination of screws, clips and also the watertight seal, whose inclusion is rendered unnecessary.

Document EP 601 347 B1 discloses a washing-machine, or combined washing- and drying-machine, in particular of a domestic type, which comprises a plastic washing tub which houses a rotating drum within which the washing load is placed; said washing tub consisting essentially of a peripheral, cylindrical, integral housing, with a rear wall and a flange-shaped front wall which incorporates protrusions, moulded separately for their subsequent joining to protrusions on the front opening of the tub by means of the fusion welding of the plastic materials of which said protrusions are made.

Welding of the tubs is usually carried out by means of placing the flat sides of the protrusions face-to-face. The protrusions of the tub and of the front wall are L-shaped in section, and by means of welding, two edges of the protrusions are mutually joined. The pressure is exerted on both joined edges of the protrusions

Welding forms part of the group of permanent joints, but unlike others such as riveting or sticking, it provides certain advantages, such as the speed of manufacture, the high resistance of the joint, and the versatility of the joining process, applicable to a great number of materials and therefore appropriate for polymers or polymer-based compound materials, as is the case with current washing-machine tubs.

In this type of washing-machine, the dampers are attached directly to the tub by means of a bolt which affixes the projecting damper to a lug formed on one of the plastic parts of the tub, or by means of a stud which goes through both the damper and two lugs formed on the two halves of the tub.

In either of these systems there is a clearance which causes the damper not to be totally fixed, thus causing a greater quantity of oscillations, vibration and noise.

DESCRIPTION OF THE INVENTION

The object of this invention is a more solid, more robust method of fixing the damper to the tub, which at the same time is cheaper and its coupling more rapid.

This objective is achieved with a plastic tub for a clothes-washing machine, in particular of a domestic type which houses a rotating drum within which the washing load is placed, said washing tub consisting of a peripheral, cylindrical housing, formed by a tub front section and a tub rear section, joined so as to enclose the drum in their interior by means of the fusion welding of the plastic and where the front tub section comprises at least one front lug and the rear tub section features at least one rear lug; said lugs face each other when the tub is closed, and to these a damper is affixed by means of a pin where said pin is formed of a single piece of plastic on one of the lugs and is joined to the other lug by means of plastic fusion welding.

Thus, as the pin is jointly fixed to the two lugs, the vibration of the same against the lug to which it is welded is eliminated, reducing in this way vibrations and noise.

Additionally, this method of fixing does not require an additional pin, as said pin is incorporated in one of the parts which form the tub, thus cheapening the joint.

The pin and the lug to which it is joined are formed from a single plastic part which includes the front or rear section of the tub. Thus, all of the above are formed as an assembly which may be produced in one moulded plastic piece.

The pin is partly hollow, cylindrical in shape and substantially circular in section, in order to facilitate its forming in the plastic manufacturing mould.

The pin, at the end which is joined to the lug by welding, incorporates a protrusion at its edge which will serve as filler material for the plastic welding process.

The damper comprises one closed ring-shaped extremity, through which the pin passes in order to guarantee a robust fixing to the tub. The pin is welded at the same time as when the front and rear sections of the tub are welded together, enclosing the drum in their interior. After positioning the damper, inserting the pin through the same, the front and rear sections of the tub are brought together face-to-face, the respective lugs also being face-to- face, so that during the same plastic welding operation the tub is closed and the damper affixed. This welding occurs at the same time as the two sections which form the tub are joined, an additional step thus being unnecessary.

The pin is formed on the rear lug of the tub, as it is into this section that the washing drum is inserted before welding the assembly closed; thus, the rear section of the tub is placed on its closed base, the drum is inserted, its shaft passing through the rear wall, the dampers are placed on the pins, and the front section is positioned, ready for welding.

The lugs comprise a through-hole mount to which the damper may be affixed, should the need arise, by means of a pin which will penetrate through all of these, in the event that the machine should require repair including the cutting of the original plastic pin.

The welding system is a system of welding by vibration, which is ideal for the joining of the two sections of the tub and the damper.

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In the event that the method of closure of the tub should be by means of clips, the welding system for welding the pin for the damper would be by ultrasonic vibration, in order to focus upon the exact point of the pin, without having to vibrate all of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description which is to be made below, and in order to aid a better understanding of the characteristics of the invention, a set of drawings is attached to this specification.

Figure 1 .- Portrays a schematic view of a washing-machine seen from the front.

Figure 2.- Portrays a detailed exploded view of the damper between the front and rear sections of the tub. Figure 3.- Portrays in detail the fixing of the damper on the pin prior to being joined to the front section of the tub. Figure 4.- Portrays in detail the joint between the front and rear sections of the tub, with the pin welded.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 portrays a schematic view of a washing-machine seen from the front in which the tub 1 is suspended from springs 7 and supported by dampers 6 within a framework. Inside the tub 1 is located a washing drum 2 into which the clothes to be washed are inserted.

Figure 2 portrays a detailed exploded view of the damper 6 between the front section 3 and rear section 4 of the tub. The extremity 61 of the damper is ring-shaped and inside the same is located a rubber ring 62 through which the free chamfered end of the pin 5, formed as an extension 51 , is inserted. The cross-sections of the two sections 3 and 4 of the tub are schematically portrayed, through their respective lugs 31 and 41 . The pin 5 protrudes from the lug of the rear section 41 of the tub.

Figure 3 portrays in detail the fixing of the damper 6 on the pin 5 prior to joining the pin 5 to the front section 31 of the tub.

Figure 4 portrays in detail the joining of the front section 31 of the tub and the rear section 41 of the tub in the region of the pin 5 where it may be seen that the material of the

extremity of the pin 51 has been melted and has produced the joint in this region. The pin 5 has been inserted through the rubber ring 62 in the extremity 61 of the damper 6.

The tub 1 is manufactured from plastic by moulding and comprises a peripheral cylindrical housing made from two parts, a tub front section 3 and a tub rear section 4 which are joined along their respective open edges, enclosing the drum 2 in their interior, by means of fusion welding of the plastic materials of the edges, producing a weld bead between the tub front section 3 and the tub rear section 4. The system for closing the same by welding is the system of closure by vibration.

In the process for closing the tub, the rear section of the tub is first placed so that it rests on its closed base and the drum 2 is inserted into the same. The dampers 6 are then placed on the pins 5 and the open side of the tub front section is placed against the assembly. Once they are engaged, the welding machine causes the front section to vibrate linearly against the rear section at a very high frequency to a width of two millimetres. The welding causes the material to melt sufficiently for the tub sections to come together by more than one millimetre, thus producing a watertight seal, and the pin 5 to be joined to the lug 31 of the front tub section with equal firmness as it is joined to the lug 41 of the rear tub section. In this way, the damper 6 is firmly attached to the tub, with no movement relative to the same except for a swinging movement around the axis of the pin 5.

In Figure 4 it may be seen how the edges of the tub sections have been melted together at their area of contact, thus enclosing the internals of the tub 1.