EP0152745B1

EP0152745B1 - Plastic tub for a laundry washing machine

Info

Publication number: EP0152745B1
Application number: EP85100216A
Authority: EP
Inventors: Arturo Cinello
Original assignee: Industrie Zanussi SpA
Current assignee: Industrie Zanussi SpA
Priority date: 1984-02-13
Filing date: 1985-01-11
Publication date: 1989-08-23
Also published as: EP0152745A2; EP0152745A3; ES8601353A1; IT8445706A0; IT1181072B; IT8445706A1; DE3572516D1; ES539434A0; ATE45776T1

Abstract

Described is a tub formed of a plastics material for a laundry washing machine of the front-loading type. According to the invention, the tub (5) is formed of two substantially cylindrical half-shells (6, 7) connected to one another in longitudinal alignment by means of bolts passing through integrally formed flanges. The tub is formed with a planar bottom portion (14, 14 min ) and a liquid discharge opening located adjacent one side thereof in direct communication with a filter body (13) integrally formed with the forward half-shell (6). The rear half-shell (7) is integrally formed with liquid inlet leans (9, 11) acting as a siphon steam trap, and mounting means for a drum actuating motor (25) Cam means (34, 35) cooperating with the rear half-shell (7) is provided for tensioning a transmission belt (41) extending between motor (25) and a drum pulley (38). The flange (3) for interconnecting the two half-shells is advantageously configured so as to permit a circulation pump (19) to be mounted thereon in communication with the filter body (13).

Description

The present invention relates to a tub formed of a plastics material and adapted to be employed in a domestic laundry washing machine of the front-loading type, and improved so as to facilitate and render more economical the manufacture and use of a machine of this type.
With a view to avoiding the difficulties and to reducing the manufacturing and maintenance costs of laundry washing machines having metal washing tubs there have been proposed various solutions employing plastic tubs. Some of these proposals have been directed to one-piece tubs integrally formed with seat means for the fixation of suspension elements, counterweights, and actuating means.
These solutions suffer from the disadvantage, however, of requiring the employ of moulds of very large dimensions and of intricate provisions for positioning numerous inserts within the mould.
In addition, the operation of mounting the various components on the tub requires the latter to be repeatedly displaced about different axes.
Also known are washing tubs for the specified purpose consisting of two half-shells bolted together.
This type of tubs suffers from the drawback of not being integrally provided with lugs or similar means for the fixation of counterweights or equilibration weights, so that these weights have to be secured to the tub by means of annular metal clamps, or have to be injected into cavities integrally formed with the tub. In the former case, the weights secured to the outer walls of the tub are formed of a cement mixture which is compressed so as to increase its density. For obvious reasons, this compression cannot be carried out on a cement mixture injected into the tub cavities, resulting in a greater volume of the cement mixture for a given weight. In addition, the cavities have to be formed with anchoring studs or the like for avoiding noisy vibrations of the cement mixture during the laundering operation.
A further disadvantage of known plastic tubs of this type results from their perfectly circular shape which requires the diameter of the tub to be substantially greater than that of the washing drum so as to define therebetween a space of sufficiently great dimensions for the installation of resistance heater elements. Under these aspects, the fact that the tub is perfectly circular obviously results in a disadvantageous increase of the space required by the tub within the housing of the washing machines at locations not required for the installation of heater elements. It is also to be noted that in conventional tubs of the type described, the discharge opening is formed exactly at the center of the lower portion of the tub, so that at least part of the detergent supplied to the tub with the first water charge enters the discharge system and remains therein without being used unless there is a recirculation passage between the discharge system and an additional opening of the tub. In addition to this inconvenience the centered location of the discharge outlet opening is disadvantageous with regard to the discharge of the laundering liquid during the centrifuging phase, as the liquid flow during this phase is directed substantially at right angles to the axis of the discharge opening. This requires the employ of baffles.for deflecting the liquid flow towards the discharge opening.
In conventional washing tubs of this type, a bellows-type discharge conduit has its distal end connected to a filter element itself connected to the intake of a discharge pump mounted in the housing of the machine. This construction obviously requires an increased number of connections and thus numerous manual operations for assembly. The same applies to the fixation of the drum actuating motor which is provided with four integrally formed seat portions adapted to be secured by means of transverse bolts and with the interposition of spacers, to corresponding studs formed with openings and projecting from the lower part of the tub. In this case, the tension of the transmission belt is adjusted by varying the position of the motor with respect to the tub. To this purpose, at least a pair of the openings formed in the studs of the tub are of arcuately elongate shape so as to permit the motor to be adjusted to the desired position. This adjustment operation likewise requires a sequence of manual operations and is practically incapable of positively achieving and maintaining the desired tension of the belt.
A further disadvantage encountered in conventional tubs results from the arrangement and construction of a rubber tubing connecting the tub to a detergent distributor and additionally acting as a syphon for trapping a quantity of water sufficient for obstructing the water inlet conduit so as to preclude the escape of steam generated during operation of the washing machine.
To this effect, the rubber tubing or a similar conduit has to be of U-shaped configuration requiring a rather complicated forming operation. It is obvious that the above described disadvantages constitute an obstacle to the assembly of the tub in an automatized process, as they require the tub to be displaced about various axes and the execution of numerous manual operations.
It is therefore an object of the present invention to provide a washing tub formed of a plastics material, in which the above noted inconveniences are eliminated and which lends itself to assembly in a highly automatized process.
These objects are attained by a washing tub made of a plastics material for a domestic laundry washing machine of the front-loading type, said tub being formed of two half-shells of substantially cylindrical shape interconnected in longitudinal alignment by means of respective flanges bolted together, and provided with means for the supply and discharge of washing liquids, means for filtering the liquids during the discharge phase, and means for the fixation of counterweights, for the adjustable mounting of drum actuating means, and for the connection of the tub to the housing of the washing machine, said tub being characterized in that the two half-shells comprise respective and adjacent lower portions of their internal surface having a planar profile, the forward half-shell comprising an integrally formed discharge opening disposed laterally of said portion, and a filter body directly communicating with said discharge opening, the rear half-shell comprising cam means for tensioning a transmission belt connecting the shaft of a motor to a pulley fixedly secured to the drum shaft.
The characteristics and advantages of the invention will become more clearly evident from the following description, given by way of example with reference to the accompanying drawings, wherein:

fig. 1 shows a rear view of a tub constructed in accordance with the invention, and
fig. 2 shows a sectional view of the tub taken along the line II-II in fig. 1.

The washing tub according to the invention is composed of two half-shells, namely, as shown in fig. 2, a forward half-shell 6 and a rear half-shell 7 formed of a thermoplastic material by compression moulding or the like method. Half- shells 6 and 7 are of substantially cylindrical shape and joined to one another, with a sealing gasket 39 therebetween, by means of flanges 3 integrally formed along the abutting edges and bolted to one another. As shown in fig. 2, the forward half-shell 6 is formed with an opening 8 for charging the drum (not shown) of the machine, with an inlet opening 9 for the washing liquid, and an opening 10 for the discharge of the liquid.
As evident from fig. 1, inlet opening 9 is formed with a tubular portion projecting from tub 5 and having a flow passage of circular cross-section restricted by a semi-circular wall 11 extending upwards from the lower edge of opening 9 in alignment with the peripheral wall of tub 5.
In this manner the tubular portion of inlet 9 participates in the formation of a syphon which is completed by a rubber sleeve 12 of a considerably simplified design as compared to known embodiments. The two half- shells 6 and 7 are formed with corresponding lower portions 14,14' of their interior wall surface having a planar profile. Planar portions 14, 14' are disposed in alignment with one another so as to constitute a substantially planar bottom of tub 5.
As shown in fig. 1, discharge opening 10 is offset with respect to the vertical axis of tub 5 and in direct communication with a filter body 13 which in the tub 5 according to the invention is advantageously formed integral with forward half-shell 6. In other words, discharge opening 10 is located adjacent a margin of planar bottom 14, 14' and at the downstream side thereof with respect to the direction of rotation (indicated by an arrow in fig. 1) of the drum containing the laundry to be laundered.
The planar configuration of the bottom of tub 5 and the integration of filter body 13 ensure that on charging tub 5 the detergent carried by the water accumulates preferentially on the planar bottom 14,14', and to a smaller degree on the bottom of filter body 13, which may itself be considered as part of the bottom of tub 5, so that the detergent accumulated thereon is put into circulation by the turbulence created by the movements of the drum.
This solution advantageously permits the elimination of the conventionally required sleeve connecting the tub to the filter body and of the additional recirculation opening in the tub and the associated conduit connecting it to the filter body. Filter body 13 is formed with an outer main opening 15 for the removable installation of a filter partition 16 integrally formed with an expansion plug 17 for hermetically sealing the filter body, and with a secondary opening 18 for connection to the intake of a circulation pump 19 with suitable sealing gaskets inserted therebetween.
Circulation pump 19 is not secured to the housing of the washing machine, but to a suitably formed flange 3 of the tub 5 according to the invention, as shown in fig. 1. This is particularly advantageous, as it reduces the necessity of manual operations for installation and thus permits the tub to be assembled in a highly automatized process.
Also to be noted is that the offset position of discharge opening 10 is effective to promote the discharge flow during the centrifuging phase, as the opening is directed opposite to the flow direction of the liquid resulting from rotation of the drum. This improves the discharge of the liquid during the centrifuging phase without the use of deflecting baffles. It is also to be noted that the planar bottom portion 14, 14' of tub 5 is effective to form an enlarged space between the tub and the drum adjacent discharge opening 10.
This enlarged space is advantageously employed for housing a resistance heater element 20 which may thus be accommodated without excessively increasing the dimensions of tub 5 so as to save valuable space within the housing accommodating the tub.
Also integrally formed with forward half-shell 6 is an annular collar 21 provided with bores for securing thereto a forward counterweight 22 by means of screws 23 cooperating with expansion dowels.
This solution for the fixation of the counterweight is also particularly advantageous with a view to completely automatized assembly of the tub.
Also formed integrally with forward half-shell 6 and projecting outwards from the bottom portion thereof is an L-shaped lug 24 forming part of the mounting means of the drum actuating motor 25, as will be explained in detail.
Integrally formed with rear half-shell 7 are flange means 26 for securing an upper counterweight 28 by means of screws 27 cooperating with expansion dowels, and an L-shaped lug 29 in coaxial alignment with lug 24 of forward half-shell 6.
The two lugs 24 and 29 are adapted to engage a corresponding pair of anchoring studs 30, 31 projecting from the body of motor 25, threaded fastener means 32 being provided to secure motor 25 to lug 24.
In addition to lugs 24 and 29, a further anchoring point is provided for motor 25 in the form of a support bracket 33 engaging a horizonzally disposed bolt 34. Bolt 34 is integrally connected to a cam 35 having a toothed cam profile extending along a spiral curve of progressively increasing radius with respect to its mounting axis.
The toothed profile of cam 35 cooperates with a toothed sector 36 formed at the lower part of rear half-shell 7 (fig. 1). As an alternative, toothed sector 36 may be formed at the base of a lug having an elongate opening for guiding bolt 34 as it follows a downwards displacement of motor 25. The free end of the toothed profile of cam 35 is connected to toothed sector 36 through a tension spring 37 biasing cam 35 together with bolt 34 in anticlockwise direction. This arrangement is effective to automatically tension a transmission V-belt 41.
In particular, transmission belt 41 is tensioned by merely pushing down motor 25 by exerting pressure on a pulley 42 secured to the motor shaft, permitting cam 35 to be rotated together with bolt 34 to a position in which its toothed profile is reengaged with toothed sector 36. In this manner belt 41 is tensioned to the desired degree with a reliability unattainable by known manual adjustment means. The described tensioning means is also useful for compensating elongation of belt 41 during operation of the laundry washing machine.
This is because cam 35 is constantly biased by spring 37 in a direction for displacing bolt 34 so as to automatically ensure proper tensioning of belt 41.
The tub 5 according to the invention also solves the problem of providing a suitably formed edge surrounding the forward loading opening 8 during the tub forming process. In conventional tubs this edge is designed to cooperate with annular clamp means for securing a bellows connecting the tub to the door opening of the housing of the washing machine.
In the tub 5 according to the invention, the edge of opening 8 is formed with an L-shaped cross- sectional profile terminating in a broadened rim 43. A connecting bellows 44 has an inner end portion formed with a channel-shaped cross-section for receiving the broadened rim of opening edge 43 and secured thereto by means of a compression ring 45 having a U-shaped profile for clampingly retaining the end portion of bellows 44 on the broadened rim 43.
The combination of the specific advantages of the tub 5 according to the invention is particularly relevant under the aspect of automatized assembly. Successive phases of the assembling process may in fact be carried out with displacements about a single vertical axis and in the following sequence:

a) mounting of the driven drum pulley 38 and assembling rear half-shell 7 with the various drive components;
b) mounting of the drum and positioning the sealing gasket 39 to be interposed between the two half- shells 6 and 7;
c) mounting and securing forward half-shell 6;
d) connecting vibration dampener plates 40 and securing counterweights 22 and 28;
e) mounting motor 25 and discharge pump 19;
f) properly tensioning drive belt 41 by exerting a suitable pressure on driving pulley 42.

The main advantages of the washing tub 5 according to the invention may be summarized as follows:

- simplification and rationalization of the moulding process;
- integration of various components directly on the tub and the resultant reduction and simplification of the assembly steps;
- the possibility of automatized assembly of the laundering assembly thanks to the possibility of mounting the various components with displacements about a single vertical axis and with reduced displacements of the various parts.

Claims

1. A plastic tub for a domestic laundry washing machine of the front-loading type, said tub being formed of two substantially cylindrical half-shells connected to one another in longitudinal alignment by means of respective flanges bolted together, and provided with means for the introduction and discharge of washing liquids, means for filtering said liquids during the discharge phase, and means for securing counterweights, for adjustably mounting elements for the actuation of the drum, and for the connection of the tub to the housing of the laundry washing machine, characterized in that said two half-shells (6, 7) include mutually adjacent lower portions (14,14') of their interior surfaces formed with a planar profile, the forward half-shell (6) having an integrally formed discharge opening (10) disposed laterally of said planar portion (14) and a filter body (13) immediately communicating with said discharge opening (10), the rear half-shell (7) having cam means (34, 35, 36, 37) for tensioning the transmission beit (41) connecting the shaft of a drive motor (25) to a pulley (38) secured to the shaft of the drum.

2. A tub according to claim 1, characterized in that said forward half-shell (6) is integrally formed with an annular collar (21) surrounding a front opening (8) of the tub (5) and adapted to have a forward counterweight (22) secured thereto by means of screws (23) cooperating with expansion dowels or the like, and with a washing liquid inlet pipe socket (9) projecting outside tub (5) and having a passage of circular cross-section restricted at the entrance into the tub (5) by a semicircular partition (11) projecting into said passage from the lower part of said pipe socket (9).

3. A tub according to claim 1, characterized in that said cam means (34, 35, 36, 37) for tensioning said transmission V-belt (41) comprise a bolt (34) extending through a perforate support bracket (33) of said motor (25), a toothed sector (36) formed at the lower part of said rear half-shell (7), and a cam (35) integrally connected to said bolt (34) and having a toothed profile extending along a spiral curve of a progressively increasing radius with respect to the axis of said bolt (34), said bolt (34) and cam (35) being biased by a spring (37) to rotate towards a position in which the toothed profile of said cam (35) engages the toothed sector (36) formed at the lower part of said rear half-shell (7).

4. A tub according to claim 1, in which said half-shells are provided with flanges for the interconnection of said half shells, with a sealing gasket positioned therebetween, and for anchoring the elements for the suspension of the tub in the housing of the washing machine, characterized in that at least one lower flange (3) is configured so as to permit a circulation pump (19) communicating with said filter body (13) to be directly mounted on said tub (5).