GB2096649A - Tub unit for a washing machine - Google Patents

Abstract

A tub unit 3 for a washing machine is described in which a container 8 for a rotary drum 7 is formed from a thin inner casing 9 of stainless steel, assembled by folding and rolling, intended to contain the washing water and to resist chemical attack, and a strong outer casing 10 of structural steel, assembled by rivetting, fitted onto the inner casing and providing for the anchorage of the suspension member 4 for the tub unit (3), counterweights 32, 33 and the drive means (25), Fig. 7 (not shown), for the drum. Suspension springs 5 are anchored in holes 5a in tie plates 16a, 16b on the casing 10 and friction shock absorbers 6 are anchored in fixtures 6a on tie plates 16c, 16d. The manufacture of the tub unit according to the invention is ecologically satisfactory and improved from an energy-saving view, giving the washing machine a smaller consumption of electrical energy, water, and detergent as well as a longer working life. <IMAGE>

Description

SPECIFICATION Tub unit for a washing machine The present invention relates to a tub unit for a washing machine, of the type in which a drum for containing the laundry to be washed is rotatably mounted in a container for the washing water which is suspended by suspension members within the cabinet of the washing machine.

As is known, in modern washing machines, the achievement of a desired washing performance and working life depends essentially on the features of the tub unit. Indeed, the tub unit is required to operate under extremely onerous conditions in that it must withstand the considerable mechanical stresses due to stresses in the suspension members, particularly in the centrifuging phase, while at the same time being resistant to chemical attack by the waterdetergent mixture, which is rendered particularly corrosive by the high temperature which it may reach.

Known tub units at present in use can fulfill the aforesaid two requirements satisfactorily, but their manufacture presents a number of disadvantages associated with their structure. Among these disadvantages are the fact that the manufacture involves the use of highly polluting manufacturing processes and machines of high energy consumption. Indeed, in the manufacture of currently known tub units wide use is made of galvanised or enamelled mechanical parts as well as various mechanical parts fabricated by welding.

The enamelling and galvanising processes result in the evolution of gases which are not compatible with the working environment and hence require the installation of costly and specially adapted air purification systems.

Welding, on the other hand, entails a high, intermittent consumption of electrical energy, resulting in high installation and operating costs.

The problem which is at the basis of the present invention is that of providing a tub unit which has structural and functional characteristics such as to satisfy the aforesaid needs while simultaneously overcoming the disadvantages mentioned with reference to the known art, and in particular a tub unit the manufacture of which is satisfactory both from an ecological and an energy-saving point of view.

The present invention resolves these problems by abandoning the conventional concept of a unitary tub unit structure and providing a composite structure which satisfies each of the said contrasting requirements individually and to good effect.

The present invention accordingly provides a tub unit of the type specified which is characterised in that the container comprises an inner casing of thin stainless steel for containing the washing water and an outer casing of structural steel fitted onto the inner casing and providing for the anchorage of the said suspension members.

Further characteristics and advantages of the tub unit according to the present invention will emerge from the following description of a preferred embodiment, given by way of nonlimiting example, with reference to the appended drawings, in which: Figure 1 is a partially cut-away, schematic perspective view of a washing machine incorporating a tub unit according to the invention; Figure 2 is a perspective view of the tub unit according to the invention; Figure 3 is a perspective view of the tub unit of Figure 2 in the direction of arrow F in Figure 2; Figure 4 is a perspective view, partially exploded, of the tub unit of Figure 2; Figure 5 is a cross-sectional view of the tub unit of Figure 2; Figure 6a is a sectional view of a detail of the tub unit of Figure 2; Figure 6b is a sectional view of the same detail as in Figure 6a after a maintenance operation;; Figure 7 is a longitudinal sectional view of a further detail of the tub unit of Figure 2, and Figure 8 is a perspective view of a constructional variant of the tub unit of Figure 2.

With reference to the appended drawings, a washing machine is generally indicated 1.

The washing machine 1 comprises a cabinet 2 and a tub unit 3 suspended centrally within the cabinet 2 by means of suspension members 4. In particular, the suspension members 4 are constituted by suspension springs 5 and friction shock absorbers 6.

The tub unit 3 comprises a perforated cylindrical drum 7 with axis X-X, intended to contain the laundry to be washed, which is mounted for rotation about the axis X-X in a container generally indicated 8 which is intended to contain the washing water and to which the said suspension members 4 are anchored.

The container 8 of the tub unit 3 according to the present invention comprises two casings 9 and 10, one within the other, and in substantial contact with each other. The inner casing 9 is intended to contain the washing water and is formed from thin stainless steel sheet. The outer casing 10 is fitted onto the inner casing 9 and is formed from structural sheet steel of a predetermined mechanical strength and is equipped for the direct anchorage thereto of the suspension members 4, as will be described below.

More particularly, the inner casing 9 comprises a sleeve 1 1 with axis X-X, a front end wall 12 and a rear end wall 13. The front end wall 12 and the sleeve 1 1"are fixed together by the folding over and rolling of their respective edges (see Figure 6a); the rear end wall 13 is also fixed to the sleeve 11 in an exactly analogous manner.

The outer casing 10 comprises an annular frontal disc 14 and a rear end wall 1 5 interconnected by four longitudinal tie plates 1 6a, 1 sub, 1 6c and 1 sod. The tie plates 1 spa, 1 sub, 1 6c and 1 6d are fixed to the annular disc 14 by rivets 17, and are fixed to the rear end wall 1 5 by means of screws 1 8 and respective nuts 1 9 of the so called self-locking type.

The end wall 15 is reinforced by a plate 20 which is rivetted to the end wall 15 by means of rivets 21. The end wall 15 and the plate 20 have central portions 15a and 20a which in axial section (Figure 7) diverge towards the axis XX and are provided with respective apertures 15b and 20b coaxial with the axis X-X. A sleeve 22 is welded coaxially around the edges of the holes 15b and 206 and is provided internally at its ends with respective bearings 24, 23 for supporting a shaft 25 for rotating the drum 7.

An outwardly projecting end 25a of the shaft 25 is conventionally provided with a pulley 26, while the opposite end 256 of the shaft 25 is provided with an arm 27 connected to the drum 7 to rotate the latter. The end wall 15 is provided with two fixing lugs 28 for a motor 29 the shaft 29a of which is fitted with a pulley 30 connected to the pulley 26 by means of a trapezoidal section endless belt 31.

The tie plates 16a, 1Sb, 16e and are angularly spaced at 900 from each other, substantially in correspondence with four edges 2a,2b,2c, and 2d of the cabinet 2. The upper tie plates 16a and 1 sub have respective holes 5a in which the suspension springs 5 are anchored while the lower tie plates 1 sic and 1 dare provided with T-fixtures 6a to which the shock absorbers 6 are anchored.

A first counterweight 32 in the form of a yoke is fitted to the upper tie plates 16a and 16b while a second counterweight 33 is fixed to the annular disc 14.

In the container 8 of the tub unit 3 according to the invention all the forces in play are thus sustained by the outer casing 10 to which the suspension members 5 and 6, the counterweights 32 and 33, the motor 29 and the shaft 25 for rotating the drum are attached. The internal casing 9 is left with the sole function of containing the washing water and providing the desired corrosion-resilient properties to resist attack.

Advantageously the inner casing 9 (Figure 5) has an oval cross-section, enclosing the cylindrical drum 7 with a limited clearance so as to define a chamber 34 of restricted volume for receiving the inlet for the water supply and for housing an electrical resistance 35 for heating the water, as necessary. The volume of water which is not used for washing is thus reduced to a minimum and hence the total consumption of water and detergent necessary for the washing, and the electrical energy needed for heating the water, are reduced.

An annular chamber 36 is defined between the rolled and folded edges of the front end wall 12 and the sleeve 11 for the insertion therein of a toroidal seal 37 (see Figures 6a and Sb). Such a seal is inserted when, in order for technical personnel to carry out maintenance operations, it is necessary for the front end wall 12 to be separated from the sleeve 11 by an incision 38 formed by a suitable tool. When the maintenance operations have been carried out, the front end wall 12 and the sleeve 11 may be re-united and the desired sealing renewed by means of the insertion ofthetoroidal seal 37.

The tub unit illustrated and described with reference to Figures 1 to 7 is of the so called frontloader type. However the tub unit of the present invention also lends itself to manufacture in a constructional variant, indicated by 3a in Figure 8, adapted for so-called top loading and which can be formed from the front-loader type by the substitution of a limited number of parts.

The main advantage of the tub unit according to the present invention lies in the fact that it may be manufactured within the constraints imposed by the working environment without requiring costly protection means, air purification means and the like since galvanising and enamelling-type processes are completely eliminated. Moreover the manufacture of the tub unit according to the invention requires a smaller energy consumption since welding operations are completely eliminated. Other savings in production are achieved by virtue of the fact that it is possible to make tub units with different dimensions and of the front-loader or top-loader type with a limited number of different parts.

A further advantage of the tub unit according to the invention is that it enables the operating conditions during servicing to be improved, replacement of the tub being made possible by dismantling of the outer casing and the inner casing and their subsequent reassembly with the restoration of the initial operating conditions.

The tub unit according to the invention also confers on the washing machine the following advantages in use: a longer working life, a smaller consumption of water and of detergent and also a smaller consumption of electrical energy.

Claims (6)

1. Tub unit for a washing machine of the type in which a drum for containing the laundry to be washed is rotatably mounted in a container for the washing water suspended by means of suspension members within the cabinet of the washing machine, in which the container comprises an inner casing of thin stainless steel for containing the washing water and an outer casing of structural steel fitted onto the inner casing and providing for the anchorage of the said suspension members.

2. Tub unit according to Claim 1, in which the inner casing comprises a substantially cylindrical sleeve and opposite end walls, the said end walls being fixed to the sleeve by folding and rolling of their edges.

3. Tub unit according to Claim 1 , in which the outer casing comprises an annular disc, an end wall, and tie members fixed to the disc and to the end wall by rivets and by screws with self-locking nuts respectively.

4. Tub unit according to Claim 3, in which the end wall of the outer casing has a reinforcing plate rivetted thereto.

5. Tub unit according to Claim 4, in which the end wall and the reinforcing plate diverge from each other in axial section towards the axis of rotation of the drum and are provided with respective bearings for supporting the ends of a shaft for rotating the drum.

6. Tub unit for a washing machine, substantially as herein described with reference to and as shown in Figures 1 to 7 or Figure 8 of the accompanying drawings.