GB2284540A - Dishwasher or laundry washing machine having rotation moulded plastic tub - Google Patents

Abstract

A dishwasher or a laundry washing machine comprises an outer cabinet and a rotation moulded plastics inner wash tank 12 forming a washing compartment which is mounted within the outer cabinet by brackets 22. In use, the inner wash tank 12 is permitted to expand thermally relatively to the cabinet. This may be achieved by allowing for a rib 27 of the tank to slide within channels formed in the brackets 22. There may be a fixed frame e.g. a door frame (6, Fig. 2) near the open end of the tub to which the tub is secured. The external connections, e.g. inlet and drain, may be located with respect to the external surface of the tank and are preferably flexible to allow for thermal expansion of the tank. <IMAGE>

Description

WASHING MACHINE In order to make washing machines for dishes, glasses, clothes etc. quiet and to provide good heat retention, they are provided with a double skin. This takes the form of an outer cabinet and an inner wash tank which is usually constructed of stainless steel. Such a stainless steel inner wash tank increases the overall weight of the dishwasher and, owing to its inevitably complex shape is relatively difficult to manufacture requiring much continuous welding. It also often provides sharp corners in which sediment may be caught, leading to unhygienic consequences.

According to the present invention a washing machine comprises an outer cabinet and a rotation moulded plastics inner wash tank forming a washing compartment which is mounted within the outer cabinet by brackets so that, in use, the inner wash tank is permitted to expand thermally relatively to the cabinet.

By rotation moulding, sometimes referred to as spin moulding, the inner wash tank, it is possible to produce it in a complex shape from a plastics material in one operation, and avoids the high tooling costs which would be associated with injection moulding. However, one inherent disadvantage of rotation moulding is that mouldings produced in such a way have a low resistance to thermal expansion. This problem is overcome in the present invention by mounting the inner wash tank in such a way that it is free to expand thermally. The inner surfaces of a rotation moulding merge into one another via smoothly curved corners so that the inside of the wash tank can easily and reliably be wiped clean.

Although the external dimension of the inner wash tank can be closely controlled, the internal dimensional tolerances are poor. It is therefore advantageous that all connections to the wash tank including connections for a washing water inlet and a drain are located with respect to the external surface of the inner wash tank. The connections for the washing water inlet and drain should also be sufficiently flexible to allow for thermal expansion of the inner wash tank.

Preferably, the brackets mounting the inner wash tank within the outer cabinet comprise two brackets fixed within the outer cabinet on opposite sides of the inner wash tank.

Each bracket is preferably a plate which is bent to define an inwardly facing channel in which is received a complementary rib in the outer surface of the inner wash tank, whereby thermal expansion of the inner wash tank causes it to slide within the channels of the brackets.

There is also preferably sufficient clearance between the inner wash tank and these brackets to allow for thermal expansion in a transverse direction. The brackets are preferably mounted towards one end of the cabinet remote from the other end through which items to be washed are inserted into and removed from the washing machine. In this case, the other end of the inner wash tank is preferably rigidly fixed around its periphery to a frame, which may be a door frame. This ensures that when the inner wash tank expands, the other end maintains its positional relationship with respect to the outer cabinet.

An example of a washing machine constructed in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a side view of the washing machine with the side panel removed and the top panel offset; Fig. 2 is a front view of the washing machine with the door and a portion of the casing removed, and the side and top panels offset; Fig. 3 is a diagrammatic rear view showing how the inner wash tank is mounted; and Fig. 4 is a side view of the diagram of Figure 3.

The washing machine shown is of the type used for cleaning glasses.

The dishwasher has a plinth 2 and a steel outer cabinet consisting of two side panels 3, a top panel 4 and a back panel 5. A frame 6 is mounted to the plinth 2 by a pair of brackets 7 and extends around an opening in the outer cabinet. The opening is closed by a door 8 mounted on hinges 9 to open about a horizontal axis. The door 8 has a conventional steel double skinned construction and is spring loaded by springs 10 to facilitate opening and closing. A control panel 11 is provided on the outer cabinet above the door 8.

An inner wash tank 12 is mounted within the outer cabinet so that the open end of the inner wash tank is fixed and sealed to the frame 6 by screws 13. The inner wash tank 12 rests on the plinth 2 and a clearance is provided at the top, sides and back of the inner wash tank.

The inner wash tank 12 has a first recess 14, providing reservoir in which the washing water is stored and heated, projecting downwardly into the plinth 2 and being connected to a washing water supply duct 15, and a drainage duct 16.

A second washing water supply duct 13 extends from the plinth 2 between the outer cabinet and inner wash tank 12 and is connected to an opening 18 the upper surface of the inner wash tank.

A rinse tank 19 containing water and a rinsing agent is provided behind and spaced from the inner wash tank 12.

A rinsing water supply duct 20 supplies rinsing water to the opening 18 in the upper surface of the wash tank.

A rotating arm (not shown) for the distribution of water within the inner wash tank 12 is mounted in central opening 21 in the bottom of the inner wash tank. A similar arm (not shown) is mounted in the opening 18. Mountings for the two arms are screwed from outside the inner wash tank 12 through holes in the inner wash tank onto a disc which is separate from the inner wash. Tightening of the screws sandwiches the inner wash tank 12 between the mounting and disc, thus securing the arms despite any variations in thickness of the inner wash tank.

In addition to being mounted to the frame 6, the inner wash tank 8 is mounted to the plinth 2 by means of a pair of plate brackets 22. These are positioned one on each side of the wash tank 8 and towards the rear of the wash tank. Each bracket is fixed to the plinth 2 by bolts 23.

Each bracket 22 projects above the plinth 2 and is bent to have a substantially C-shape cross section with an outwardly extending part 24, a part 25 extending parallel to the side panel 3 of the outer cabinet, and an inwardly extending end portion 26. The inner wash tank 12 is moulded with a rib 27 on either side which is complementary to the C-shape channel of the bracket 22. This rib is adjacent to an inwardly projecting rib 28 which provides support for a tray (not shown) within the inner wash tank 12.

The inner wash tank 12 is formed by a rotational moulding technique. First, a mould corresponding to a external surface of the inner wash tank is produced. A semi liquid plastics material is then sprayed from a source onto the inner surface of the mould so that the plastic is spread by a centrifugal force evenly on the inner surface of the mould. Mouldings produced in this way are difficult to machine, and the mould should therefore be such that the amount of machining required is kept to a minimum.

In use, water fills the recess 14 and is heated. This water, together with a detergent is distributed around the inner wash tank 12 by the rotating arms. The used water drains back into the recess 14 through a perforate drain plate (not shown) covering the recess 14, where it is stored for the next washing cycle. Some of this water is periodically replaced. Rinsing water from a rinse tank 19 is then supplied to the inner wash tank 12 through the rinse water supply duct 20 and upper rotating arm. This also drains into the recess 14.

The hot water within the wash tank 12 causes it to expand. As the inner wash tank is rigidly fixed at its front end, it is forced to expand rearwardly into the outer cabinet. Such expansion is readily accommodated by the ribs 27 sliding within the brackets 22. Thermal expansion of the inner wash tank 12 across the width of the outer cabinet is accommodated by a slight clearance between the brackets 13 and the inner wash tank 12.

All of the external connections, i.e. for the supply of water from the mains and a drain connection, are made to the plinth 2. All of the connections to the inner wash tank 12 are made with flexible pipes. This allows any thermal expansion of the inner wash tank 12 to be readily accommodated.

Claims (9)

1. A washing machine comprising an outer cabinet and a rotation moulded plastics inner wash tank forming a washing compartment which is mounted within the outer cabinet by brackets so that, in use, the inner wash tank is permitted to expand thermally relatively to the cabinet.

2. A washing machine according to claim 1, wherein all connections to the wash tank including connections for a washing water inlet and a drain are located with respect to the external surface of the inner wash tank.

3. A washing machine according to claim 2, wherein the connections for the washing water inlet and drain are sufficiently flexible to allow for thermal expansion of the inner wash tank.

4. A washing machine according to any one of claims 1 to 3, wherein the brackets mounting the inner wash tank within the outer cabinet comprise two brackets fixed within the outer cabinet on opposite sides of the inner wash tank.

5. A washing machine according to claim 4, wherein each bracket is a plate which is bent to define an inwardly facing channel in which is received a complementary rib in the outer surface of the inner wash tank, whereby thermal expansion of the inner wash tank causes it to slide within the channels of the brackets.

6. A washing machine according to claim 4 or claim 5, wherein there is sufficient clearance between the inner wash tank and the brackets to allow for thermal expansion in a transverse direction.

7. A washing machine according to any one of claims 4 to 6, wherein the brackets are mounted towards one end of the cabinet remote from the other end through which items to be washed are inserted into and removed from the washing machine.

8. A washing machine according to claim 7, wherein the other end of the inner wash tank is preferably rigidly fixed around its periphery to a frame, which may be a door frame.

9. A washing machine substantially as described with reference to the accompanying drawings.