GB2219849A

GB2219849A - Noise reduced tumble dryer

Info

Publication number: GB2219849A
Application number: GB8913805A
Authority: GB
Inventors: Anna Osvaldo Dell
Original assignee: Industrie Zanussi SpA
Current assignee: Industrie Zanussi SpA
Priority date: 1988-06-17
Filing date: 1989-06-15
Publication date: 1989-12-20
Anticipated expiration: 2009-06-15
Also published as: FR2632985B3; IT218171Z2; DE8904738U1; GB2219849B; GB8913805D0; IT8834029V0; FR2632985A3

Abstract

A domestic tumble dryer has a rotary drum provided with an improved noise prevention device. The tumble dryer has a drum rotating about a horizontal axis, with an internal pneumatic circuit connected to the external atmosphere through at least one suction inlet provided coaxially to a fan of the centrifugal type designed to suction air from outside and force it through the pneumatic circuit in a direction substantially at right angles to the direction of suction, the suction inlet (12) being provided with a static defector (14) which causes a helical rotation of the streams of air suctioned in by the fan (9). <IMAGE>

Description

DOMESTIC TUMBLE DRYER The present invention relates to a domestic tumble dryer of the type with a rotary drum provided with an improved noise prevention device.

This type of dryer substantially comprises a fan which takes air from the atmosphere outside the dryer and supplies it through heating devices, the laundry drum and finally either through a duct discharging into the external atmosphere, if the machine is of the type with an open circuit for the drying air, or to a condensation unit with water or air cooling, if the machine is of the type with a closed circuit for the drying air.

In both types of operation, the intake of air from the surrounding atmosphere causes unpleasant noise as a result of the abrupt change of direction to which the suction fan, generally of the centrifugal type, subjects the current of air which is suctioned in from outside in a first direction and is then forced through the ducts of the machine in a direction which is almost at right angles to the direction of suction.

This noise is more intense in cases in which the fan is disposed in the immediate vicinity of the suction inlet and has to supply air at a high rate of flow for an open pneumatic circuit such as, for instance, the cooling air circuit of the condensation unit.

In the conditions described above, the noise caused by the fan and the movement of the air is propagated externally without advantageous shielding by the body of the apparatus as is the case, in contrast, with closed pneumatic drying circuits.

Moreover, this type of noise caused by the fan and the eddying and turbulent movement of the air is particularly noticeable if the suction inlets are provided in the front part of the dryer so that it can be fitted without any detrimental effects on the suction of the dryer.

Tumble dryer manufacturers generally pad or cushion the ducting in the suction zone of the fan with noise-absorbing material (for instance felt or the like) to prevent this type of noise. These noise-absorbing devices are, however, difficult to apply and have to be attached in ways which complicate the assembly and maintenance operations for the dryer.

It is therefore desirable, and this is the main object of the invention, to provide a tumble dryer in which the noise of the suction air is reduced or at least minimized while at the same time providing for increasingly rational and simple assembly and maintenance of the dryer.

These and other objects are achieved in accordance with the invention with a tumble dryer, particularly of the domestic type with a drum rotating about a horizontal axis, comprising an internal pneumatic circuit connected to the external atmosphere through at least one suction inlet provided coaxially to a fan of the centrifugal type designed to suction air from outside and force it through this pneumatic circuit in a direction substantially at right angles to the direction of suction, characterized in that the suction inlet is provided with a static deflector which causes a helical rotation of- the streams of air suctioned in by the fan.

The characteristic features of the invention are set out in detail in the following description given by way of non-limiting example, with reference to the attached drawings, in which: Fig. 1 is a view, partly in section, of part of the front wall of a tumble dryer of the invention; Fig. 2 is a longitudinal section along the line II-II of Fig. 1; Fig. 3 shows a detail of Fig. 2 on an enlarged scale.

The tumble dryer 3 shown in the Figures is of the type with a drum rotating about a horizontal axis with a closed circuit for the drying air.

The dryer 3 substantially comprises an external casing 4 which houses the drum 5 for the laundry, a closed circuit for the drying air and an open circuit for the cooling air for a condensation device (not shown).

The dryer is provided with all the mechanical and electrical components needed for its operation which do not need to be described in further detail as they are sufficiently known.

The front wall 6 of the dryer 3 has suction slots 8 in the zone of the casing 4 lying below the opening 7 via which the laundry is loaded in the drum 5.

At the location of these suction slots 8, the dryer 3 houses a suction unit for the air needed to cool the condensation device mentioned above.

The suction unit comprises a centrifugal fan 9 mounted in a spiral housing 10 and operated by an electrical drive motor 11 (Fig. 2).

The housing 10 of the fan 9 has an circular suction inlet 12 coaxial with the fan 9 and is connected to the condensation unit mentioned above by a duct 13 whose initial portion extends almost at right angles to the direction of the air passing through the slots 8 and the suction inlet 12.

In a conventional tumble dryer, this abrupt change of direction causes the current of air suctioned in by the fan 9 to eddy which consequently leads to an undesirable increase in the noise of the dryer.

In the tumble dryer of the invention, this type of noise is eliminated or at least minimized by the use of a static deflector 14 disposed at the suction inlet 12 of the fan 9. This deflector 14 substantially has the shape of a "flower" (Fig. 3) and comprises a rounded perimetral edge 15, a central rod 16 and a plurality of radial blades 17 fixed between the edge 15 and the rod 16 with an inclination of approximately 450 with respect to the plane bounded by the suction inlet 12.

The radial blades 17 cause the streams of air suctioned in to rotate which is advantageous for the purposes of silencing the operation of the machine.

It was observed during laboratory tests that the streams of the current of air suctioned in by the fan 9 meet the elbow curve of the suction duct 13 at an angle likely to reduce both the formation of eddies and turbulence and the noise resulting therefrom.

It was also observed that the deflector 14 effectively shields the outside environment from the remaining noise of the dryer.

The sound waves which tend to propagate outwardly towards the suction inlet 12 are to a large extent reflected towards the interior of the dryer 3 by the radial blades 17 of the deflector 14.

Although the deflector 14 is mounted by way of example above the suction inlet 12 for the cooling air for the condensation unit, it is obvious that it could also be advantageously used on any other suction inlets of the dryer 3.

The objects of the invention, i.e. reducing the suction noise of the apparatus in a simple and rational way without having to use soundabsorbing materials which have a detrimental effect on the assembly and maintenance operations for the dryer, are therefore achieved.

The deflector 14 could obviously be subject to modifications and variants without thereby departing from the scope of the characteristic features set out in the attached claims.

For instance, the deflector 14 can also be formed as an integral part of the suction slots 8 when the spiral housing 10 of the fan 9 is constructed in close contact with the front wall 6 of the dryer 3.

Claims

1. Tumble dryer, particularly of the domestic type with a drum rotating about a horizontal axis, comprising an internal pneumatic circuit connected to the external atmosphere through at least one suction inlet provided coaxially to a fan of the centrifugal type designed to suction air from outside and force it through the pneumatic circuit in a direction substantially at right angles to the direction of suction, characterized in that the suction inlet (12) is provided with a static deflector (14) which causes a helical rotation of the streams of air suctioned in by the fan (9).

2. Tumble dryer as claimed in claim 1, characterized in that the deflector (14) has the shape of a "flower" and comprises a rounded perimetral edge (15), a central rod (16) and a plurality of blades (17) disposed radially between the edge (15) and the rod (16) and inclined substantially at 45C with respect to the plane bounded by the suction inlet (12).