GB2217352A

GB2217352A - Steam irons

Info

Publication number: GB2217352A
Application number: GB8908007A
Authority: GB
Inventors: Stephen Leonard Rawle
Original assignee: Kenwood Ltd
Current assignee: Kenwood Ltd
Priority date: 1988-04-14
Filing date: 1989-04-10
Publication date: 1989-10-25
Also published as: GB8808813D0; GB8908007D0

Abstract

A steam iron, especially a cordless iron comprises a steam chamber (5) provided with its own independent heating means. Preferably sole plate 2 has a separate heating means. Steam chambers may be part of an aluminium heat store 4 heated by a PTC heating element or a mica laminate heating element and associated thermostat. The provision of independent heating means for the sole plate and the steam chamber substantially eliminates heat loss from the sole plate due to steam generation and additionally enables steam to be generated even when the sole plate is operating on a relatively low temperature setting; this may be advantageous when ironing certain kinds of delicate fabrics. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO IRONS This invention relates to steam irons, and especially but not solely to steam irons of the cordless variety.

Conventional cordless steam irons comprise a steam chamber situated over the iron sole plate with a heating element fixed on the sole plate for generating steam from water fed into the steam chamber by means of an iron needle valve. Thus in irons of this kind the heating element performs two functions: that of generating steam and that of heating the sole plate. Such a cordless iron once removed from its base unit has a very limited amount of time in which to maintain a useful operating temperature and has to be returned to its base unit frequently for reheating of the heating element.

An additional disadvantage of such cordless steam irons is that in order to generate sufficient steam efficiently the heating elements must operate at a very high temperature and consequently the sole plate of the iron is also heated to a high temperature; this may be a considerable disadvantage when the iron is being used to iron certain kinds of delicate fabrics.

It is therefore an object of this invention to provide a cordless iron which overcomes the aforementioned disadvantages.

According to the invention there is provided a steam iron comprising a sole plate and a steam chamber which is provided with its own independent heating means.

According to another aspect of the invention there is provided a steam iron comprising a sole plate and a steam chamber each of which is provided with its own independent heating means.

The provision of independent heating means for the sole plate and the steam chamber substantially eliminates heat loss from the sole plate due to steam generation and additionally enables steam to be generated even when the sole plate is operating on a relatively low temperature setting.

At temperatures not conventionally associated with steam ironing or with no heat applied to the sole plate, it is envisaged that the sole plate may be made of plastic. Such a sole plate may be moulded in plastic, suitable thermoplastic materials such as polybutylene terephthalate (PBT) may be considered for such a purpose.

In a preferred embodiment of the invention the independent heating means of the steam chamber comprises a Positive Temperature Coefficient (PTC) device.

A PTC device is particularly suitable for this purpose providing as it does a high initial power level at low temperatures and therefore heating up quickly.

In a further embodiment of the invention the steam chamber includes a heat retaining means. Such a heat retaining means serves to enhance the production of steam in the steam chamber.

Preferably, the heat retaining means incorporates the steam chamber. Such an embodiment of the invention enhances the production of steam in the steam chamber still further.

In a yet further embodiment of the invention the steam iron is a cordless steam iron. It is in such cordless steam irons that the substantial elimination of heat loss from the iron sole plate, as achieved by the invention, is particularly beneficial, enabling the cordless steam iron of the invention to maintain a useful operating temperature for a much longer time than prior art cordless steam irons. In addition, a cordless steam iron embodying the invention can be reheated much more quickly than prior art cordless steam irons, due to the ability of simultaneously heating the two independent heating elements.

The provision of a PTC device as the independent heating means of the steam chamber decreases reheating time still further.

A specific embodiment of the invention will now be described, by way of example only, with reference to the accompanying sole drawing, which shows a schematic vertical cross-section of an iron embodying the invention.

A cordless steam iron shown generally at 1 comprises a sole plate 2, water tank 3 and heat store 4. The heat store 4 incorporates a steam chamber 5; a needle valve 6 provides a connecting passageway for water from tank 3 to chamber 5. The sole plate 2 is heated by a thermostatically controlled heating element (not shown) and a further heating element 7 provides the heating means for the heat store 4. A second thermostatically controlled heating element (not shown) is provided in the iron sole plate 2.

The heat store 4 is made from aluminium (die cast or extruded) but can alternatively be made from some other suitable metal or non-metallic substance with appropriate heat storage properties.

To enable rapid heating of the element, the heating element 7 has a low thermal mass. A particularly suitable device for this purpose is a positive temperature coefficient (PTC) heater, such a heater providing a high initial power level at low temperatures and therefore heating up quickly. As the temperature rises, the power level decreases; so the heater effectively self limits at a predetermined operating temperature and a self-regulating heater is thus provided. A suitable alternative to a PTC heater for the heating element 7 is a mica laminate element; however such elements are not self-regulating and require thermostats to limit them.

When the cordless steam iron 1 is required to be used, it is placed on an electrical base unit (not shown) where it makes electrical contact with connectors in the base unit which are powered from the mains supply. Whilst connected to the base unit the sole plate 2 and heat store 4 are heated up by means of their respective heating elements. The sole plate element is a standard variable-thermostat sheathed element and thus heats up to the value selected by the user. The heating element 7 is, as described earlier, a self-regulating PTC element and operates at a predetermined optimum temperature for steam generation.

When the two heating elements have reached their respective desired temperatures the iron is removed from its base and is ready for use.

In operation, water drips from the water tank 3 into the steam chamber 5 by means of the needle valve 6. On entering the steam chamber 5, the water is converted into steam by the heat store 4. A plurality of ducts (not shown) channel the steam from the steam chamber 5 through parts (not shown) provided in the sole plate 2.

The thermal mass and operating temperature of heat store 4 are chosen so that sufficient heat can be stored to provide steam generation for one minute. The heat store 4 is not thermally connected to the sole plate 2 and the provision of this independently heated heat store 4 substantially eliminates heat loss from the sole plate 2 due to steam generation. A consequence of this is a considerably increased ironing time over prior art cordless steam irons, which rely upon one heating source for both steam generation and sole plate heating.

An additional advantage of providing a thermostatically controlled heating element for the sole plate and a separate heating element for steam generation, is that steam can still be generated even when ironing clothes on a relatively low sole plate setting thus making it possible to steam iron delicate fabrics. Also, because the sole plate is not used to produce steam, as in conventional steam irons, the sole plate heat loss is reduced, giving a slower rate of temperature fall, resulting once again in increased ironing time.

Once the iron has ceased to function usefully, due to cooling, it is replaced on its base unit and the two heating elements are reheated to the required temperature. This reheating process is much quicker than on conventional cordless steam irons because of the simultaneous heating of heat store element 4 and sole plate 2 and because of the use of the quick heating PTC device as the heating element 7.

The use of a separate PTC element for steam generation need not be confined to cordless steam iron, but could be extended to conventional corded steam irons to provide steam generation regardless of sole plate operating temperatures, thus enabling steam ironing at low sole plate temperatures.

Claims

1. A steam iron comprising a sole plate and a steam chamber each of which is provided with its own independent heating means.

2. A steam iron comprising a sole plate and a steam chamber which is provided with its own independent heating means.

3. A steam iron according to Claim 1, the sole plate being made of plastic(s) and being thermostatically controlled to operate at temperatures suitable for such plastic(s).

4. A steam iron according to Claim 2, the sole plate being made of plastic(s).

5. A steam iron according to Claim 3 or 4, the sole plate being moulded.

6. A steam iron according to Claims 1 to 5, the independent heating means of the steam chamber comprising a Positive Temperature Coefficient device.

7. A steam iron according to Claims 1 to 5, the independent heating means of the steam chamber comprising a mica laminate element and associated thermostatic device.

8. A steam iron according to Claims 1 to 7, the steam chamber including a heat retaining means.

9. A steam iron according to Claim 8, the heat retaining means incorporating the steam chamber.

10. A steam iron as stated in any of the preceding claims where the steam iron is a cordless steam iron.

11. A steam iron being substantially as hereinbefore described with reference to and illustrated by the single figure of the accompanying drawing.