GB2095806A - Tumble drier - Google Patents

Abstract

A tumble drier comprises a drum 5, mounted in a cabinet 1 and rotatable about a horizontal axis by a motor 8, and an air impeller 9 which causes air to be drawn over a heater 15 and through the drum from one end to the other. The heater 15 is arranged between one end of the drum 5 and an adjacent wall 3 of the cabinet and is mounted on a plate 12 arranged between the heater 15 and the said wall 3. Before being drawn over the heater 15, the air passes through an annular gap 13 formed between the edge region of the plate and the one end of the drum 5. The wall 3 is provided with at least one air inlet aperture 11 behind the plate 12 so that, in use, air is drawn into the cabinet 1 via the aperture(s) 11 and, before being drawn through the gap 13, passes over at least a major portion of the surface of the plate 12 facing the wall 3. The heater 15 may be connected to a thermostat responsive to the temperature of the plate 12. <IMAGE>

Description

SPECIFICATION Tumble drier This invention relates to a laundry tumble drier comprising a drum mounted in a cabinet and rotatable about a horizontal axis by a motor and an air impeller which causes air to be drawn over a heater and through the drum from one end to the other, which heater is arranged between said one end of the drum and an adjacent wall of the cabinet and is mounted on a plate arranged between the heater and the said wall.

Such a drier provides effective drying means for articles of a laundry load placed in the drum. One drier of this kind, disclosed in United States Patent No. 3,226,842, has a door for unloading the drum located at the front of the cabinet whilst the electric heating element is mounted with its plate adjacent the rear wall of the cabinet. This mounting of the heating element can lead to the plate and the cabinet rear wall being heated to unsuitably high temperatures. These temperatures occur because it is usually necessary to conserve space in the place where the drier is to be used and concequently the cabinet wall, the plate and the element are placed as close together as possible in order to reduce the front-to-rear depth of the drier. In addition, the drier may be pushed with its rear surface up against the wall of a room in which the drier is used.These conditions can cause excessive heating of the cabinet rear wall which may lead to damage to any surface finish on this wall. In addition, thermal energy is lost from this cabinet wall and it would be better for making efficient use of all the electric power consumed by the drier if this thermal energy could be applied to accelerate the clothes-drying process.

We have now discovered a way of keeping the cabinet rear wall sufficiently cool so that wastage of thermal energy is kept to a minimum.

According to the invention, there is provided a tumble drier of the kind defined in the opening paragraph hereof, characterised in that the arrangement is such that, before being drawn over the heater, the air passes through an annular gap formed between the edge region of the plate and the one end of the drum, and the said wall is provided with at least one air inlet aperture behind the plate such that, in use, air is drawn into the cabinet via said aperture(s) and, before being drawn through said gap, passes over at least a major portion of the surface of the plate facing said wall.

This construction includes at least one air inlet aperture located in the cabinet wall behind the plate such that air entering the cabinet through this aperture flows over the rear surface of the plate. The plate thus becomes cooled by the resulting air flow and the entering air becomes preheated before it passes through the annular gap to the heater. In this way, heat absorbed by the plate can be transferred to the entering air so that this heat can be made use of in the drum. If the cabinet includes a further opening for air in addition to the aperture behind the plate, then the air from this further opening may be allowed to mix with that preheated by the plate in order to provide some initial heating of the whole air stream before this passes through the annular gap.

In one embodiment, the gap is so dimensioned and located with respect to the heater that substantially all the air drawn through said gap is directed towards the heater. This ensures that all of the air passing into the drum is heated so that the total volume of air will be fully effective in removing moisture from the laundry load in the drum.

In a further embodiment, the heater is electrically connected to a thermostat which is responsive to the plate temperature. This provision ensures that if the plate should become overheated, for example by a failure of the motor driving the impeller or by a blockage of the aperture(s) in the cabinet, then the thermostat will operate to switch off the heater before any danger can arise from an excessive increase in the plate temperature.

In another embodiment, the heater is mounted with a thermal cutout which is arranged to break the electrical circuit to the heater in the event of overheating thereof. This thermal cutout will operate even in the event of failure of any other safety device to ensure that if the temperature of the heater itself should rise very far above its normal operating temperature then the electrical circuit to the heater will be interrupted.

By way of example, a particular embodiment of the invention will now be described with reference to the accompanying drawing, the single figure of which shows a sectionalized view of the drier of the invention.

The accompanying drawing is a simplified schematic layout of a tumble drier comprising a cabinet 1 having a front wall 2 and a rear wall 3. A door 4 is mounted on the front wall 2 and is openable to give access to the interior of a rotatable drum 5 which is provided at its rear end wall 6 with a central pivot 7 (shown schematically only) to enable the drum to be rotated about its horizontal axis by a motor 8 via a belt or other drive means (not shown).

Motor 8 also drives an impeller 9 which draws air into the cabinet via inlet apertures 1 1 in rear wall 3, over the rear surface of a circular baffle plate 12 centrally fixed to the rear wall, through an annular gap 13 formed between the periphery of the baffle plate 12 and an annular projection 14 on the rear end wall 6 of the drum 5, over a pair of substantially circular heating elements 15, through apertures 16 in the rear wall 6 of drum 5, through the drum and any laundry therein, through an annular gap 17 formed between the door 4 and an annular lip 18 on the front end wall 19 of the drum 5, through a perforated protection flange 21 on door 4, through a suction duct 22 surrounding door 4, and through impeller 9, whereafter the drawn-in air is expelled from the cabinet via an outlet duct 23 and an outlet vent 24.In the embodiment shown, air is also drawn into the cabinet 1 via an inlet vent 25 in the front wall 2.

The general directions of air flow in the cabinet are shown by arrows.

For the purpose of ease of understanding the air flow, the embodiment shows the air inlet vent 25 in the front wall of the cabinet and the outlet vent 24 in the rear wall. It is to be understood that vent 25 is optional both as to its provision and location.

Vent 24 may alternatively be located elsewhere in the cabinet, for example at the bottom of the front wall 2 of the cabinet.

If it is assumed, for the purpose of explanation, that the air inlet apertures 1 1 were not provided, the heat transferred to the baffle plate 12 from the heating elements 1 b would serve largely to heat the rear wall 3. Thus the heat would not only be wasted but would also cause over-heating of the rear wall and possible consequent damage to adjacent equipment. The provision of inlet apertures 1 1 overcomes both these problems.

Firstly, the cool air passing over the rear surface of baffle plate 12 keeps the plate cool and substantially prevents any rise in the temperature of the rear wall. Secondly, the heat in the plate is used to pre-heat the air entering the annular gap 13 and, therefore, is not wasted. Thus the efficiency of the drier is increased.

It is to be understood that some of the details which are generally known in tumble driers but which are not relevant to the invention are not shown in the Figure. Thus, for example, the door is provided with an air-tight seal to the front wall of the cabinet to prevent air being drawn in through the gap therebetween. Also, the front end of drum 5 is rotationally supported by the annular lip 18 riding on an annular flange 26 forming part of the suction duct housing.

Although the embodiment specifically described is a front loading drier it will be clear that the invention is equally applicable to a drier of a top loading kind. For a top loading drier, access to the drum could be obtained through a door located in the top surface of the cabinet and a second door located in the curved surface of the drum. The ends of the drum could lie close to the respective side walls of the cabinet, and the plate carrying the heater would be located between one of these ends and the adjacent cabinet side wall.

Claims (5)

1. A tumble drier comprising a drum mounted in a cabinet and rotatable about a horizontal axis by a motor and an air impeller which causes air to be drawn over a heater and through the drum from one end to the other, which heater is arranged between said one end of the drum and an adjacent wall of the cabinet and is mounted on a plate arranged between the heater and the said wall, characterised in that the arrangement is such that, before being drawn over the heater, the air passes through an annular gap formed between the edge region of the plate and the one end of the drum, and the said wall is provided with at least one air inlet aperture behind the plate such that, in use, air is drawn into the cabinet via said aperture(s) and, before being drawn through said gap, passes over at least a major portion of the surface of the plate facing said wall.

2. A drier as claimed in Claim 1, wherein the gap is so dimensioned and located with respect to the heater that substantially all the air drawn through said gap is directed towards the heater.

3. A drier as claimed in Claim 1 or 2, wherein said heater is electrically connected to a thermostat which is responsive to the plate temperature.

4. A drier as claimed in any one of Claims 1 to 3, wherein said heater is mounted with a thermal cutout which is arranged to break the electrical circuit to the heater in the event of overheating thereof.

5. A tumble drier substantially as hereinbefore described with reference to the accompanying drawing.