Steam Iron

This invention relates to a steam iron, and particularly to a steam iron which is better adapted to provide steam in an economical and effective manner.

Steam irons are well-known. Typically a heated soleplate is periodically supplied with water from a tank in the body of the iron. On reaching the inner side of the soleplate, the water is instantly vaporized, and steam exhausts through vents in the soleplate where it can aid in removing creases from the material being ironed.

In a simple embodiment an iron may be usable with or without the steam supply selected. When steaming is selected, two options are generally available. Continual or continuous steaming may be selected whereby a substantially constant supply of steam issues from the sole plate; the steam iron may allow user variable setting of this steaming function. Alternatively or additionally, a 'steam burst' function may be provided for on demand production of a steam. There is a practical limit on the ability of a soleplate to vaporize water, because each vaporization event will tend to cool the soleplate. Thus a compromise is required by which steam production is restricted to by the energy input to the soleplate.

For many steam iron users, the provision whereby a burst of steam can be provided on demand is useful, for example to deal with heavy creasing. Typically a 'steam burst' button is provided on the handle of the iron. Manually selected bursts of steam can however be provided only if the soleplate is at the necessary temperature, for otherwise a jet of very hot water may exhaust the soleplate vent and wet the material being ironed.

US-A-5010664 proposes a steam iron in which steam bursts are provided automatically at a pre-determined interval. Such an arrangement reduces fatigue of the user since a manual depression of a steam burst button is not required for each steam burst. A suitable electric drive and time controller is provided. A regular steam burst sequence is initiated and ceased by the user, and may be for a variable period

selected on demand by the user, or for a fixed period; in the latter case the user may have a control to permit variation of the fixed period during which steam bursts occur.

Repeated bursts of steam may provide too much moisture notwithstanding the prior art control mechanisms. As a result ironing may take longer because the user must cease the steam fiαnction in order to dry the material being ironed. Excessive steam production also results in a cooler soleplate, so that drying by ironing takes longer. It would be desirable to reduce water consumption whilst maintaining effective stream iron performance.

According to the invention there is provided a steam iron having user selectable steaming on demand, and comprising steam control apparatus adapted to provide an initial steam event followed by one or more subsequent steam events of reduced flow rate and/or reduced volume.

Accordingly, the amount of steam issuing from the soleplate is reduced after the initial steam event.

In this specification the term 'steam burst' is used to indicate an individually initiated and identifiable burst of steam. Such a steam burst may occur in conjunction with continual or continuous steaming, or may be initiated in otherwise dry ironing.

In the preferred embodiment said initial steam event is a steam burst, followed by one or more steam bursts of lower volume. The subsequent steam burst(s) may be at a fixed interval, or may be at a variable interval determined by for example soleplate temperature or a user selection.

Preferably subsequent steam events are inhibited in the event that soleplate temperature falls below a pre-determined cessation temperature. Such an arrangement obviates accidental release of hot water rather than steam. Subsequent steam events are preferably re-instated after soleplate temperature has recovered above a reinstatement temperature above said cessation temperature.

The subsequent steam events, being of lesser amount, reduce water consumption whilst maintaining a steam supply to aid in effective removal of creases. A single subsequent steam event may be constituted by a substantially continual series of distinct low volume steam events; the lower the volume of water being vaporized, the more frequently the soleplate can accommodate steaming.

Preferably the time delay between the start of the initial steam event and the start of the next subsequent steam event is in the range 2-4 seconds, most preferably about 3 seconds. Thereafter, additional subsequent steam events preferably occur at intervals of 5-7 seconds, most preferably about 6 seconds.

Preferably the subsequent steam events exhaust 60% or less of the initial steam event. Most preferably the subsequent steam event exhausts 30-50% or less of the initial steam event.

Other features of the invention will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings in which:-

Fig. 1 is a vertical section through the front portion of a steam iron incorporating the invention;

Figs. 2a and 2b are transverse sections through a water valve of Fig. 1, in the closed and open conditions;

Figs. 3 a and 3b are enlarged scrap sections of the valve seat area of Figs. 2a and 2b;

Figs. 4-7 shows typical on/off control sequences for the iron of the invention.

With reference to the drawings, the nose of a steam iron (10) is illustrated in Fig. 1, and comprises a handgrip (11), a main body (12), a soleplate (13), a water tank (14), a water admission valve (15) and a steam burst button (16). A printed circuit board

(PCB) (17) comprises an electronic controller for the water admission valve (15), as will be further described. The soleplate (13) includes a conventional heating element (not identified) and a temperature sensor (18).

The water admission valve (15) is shown in greater detail in Figs. 2a and 2b, and comprises an upright tubular body (21) having a cylindrical valve spool (22) movable therein from a seated condition (Fig. 3a) to an open condition (Fig. 3b). The body (21) includes an electrical solenoid coil (23) constituting an electro-magnet, and an armature (24) movable axially with respect to the coil on electrical energization thereof.

In the seated (unenergized) condition, the armature (24) is biased downwardly by a coil spring (25) to close the spool (22) against a circular valve seat (26) of the body

(21) (Fig. 3a).

An annular elastic diaphragm (31), for example of synthetic rubber, bridges the spool

(22) and body (21) to close an outlet port (32) from the water tank.

When the coil is energized via electrical leads (27), the armature (24) rises against the force of spring (25) to abut an end stop (28). At the same time the armature lifts the spool (22) and in turn the diaphragm (31), which rolls up to open the outlet port (32). The spool moves away from the seat (26) (Fig. 3b) to permit water to pass, whereupon it reaches the inner side of the soleplate (13).

Other types of the water admission valve are suitable for use with the invention.

In the open condition, the spool (22) allows a predetermined flow rate of water through the precise annular gap (33) at the seat (26) (Fig. 3b). The gap (33) may be set and/or adjusted by moving the end stop (28), for example via a screw-threaded connection to the tubular body (21 ).

The PCB (17) determines energization of the coil (23) in accordance with operation of the steam burst button (16). The PCB preferably inhibits energization of the coil if the

soleplate is not at the required temperature, as sensed by the sensor (18). In use the coil may be energized at a desirable frequency so as to release water to the soleplate at a required rate.

According to the invention, the PCB (17) determines two kinds of steam event. A first steam event releases a relatively large amount of steam in a relatively short time, and is a result of energizing the coil at a first frequency, for example as illustrated in Fig. 4. This steam event, typically a steam burst, ceases after a short period, and the number of energizations of the coil (23), i.e. on/off cycles, may be as low as one.

A second steam event releases a lesser amount of steam, for example a steam burst of lower volume, and is a result of energizing the coil (23) at the same frequency but for a shorter 'on' time, as illustrated in Fig. 5. The second steam event provides a lower overall steam flow rate suitable for continued ironing without risk of wetting the material being ironed. Furthermore the lower volume of water which is released during a second steam event tends to cool the soleplate less, and accordingly the required heat input to maintain an average soleplate temperature is reduced. A further advantage of reduced cooling is that the soleplate is better able to dry clothing which has been dampened during the first steam event, because the temperature of the soleplate is maintained closer to the thermostatic cut-off.

In an alternative the second steam event may be as a result of energizing the coil (23) at a lower frequency, as illustrated in Fig. 6, or at a combination of lower frequency and shorter 'on' time, as illustrated in Fig. 7.

It will be understood that high frequency energization of the coil 23 may cause the valve spool 22 to maintain a position midway between fully closed and fully open, and that adjustment of said frequency may cause the spool to adopt a more open or more closed condition. Alternatively the coil may be energized to move the spool solely from closed to open, and vice-versa so as to release a predetermined volume of water to the soleplate.

The comparative volume of steam in the first and second steam events may be pre-set, or may be adjustable by the user. In particular the volume of steam in the second steam event may be user selectable by for example a rotary control, to increase or decease the coil energization period between certain pre-defined limits. The maximum period for a second steam event may for example be 60% of a first steam event, and the minimum may be 30%.

The steaming time of the first and second steam events (during which several valve energizations may occur) may be pre-set or may be user selectable. For example a first steam event may cause steam emission for 1-2 seconds, whereas a second steam event may last for a longer period, for example 2-4 seconds.

The period between a first and second steam event may also be pre-set or user selectable. Typical periods are 3 seconds between the first and second steam event, and 6 seconds for subsequent steam events.

Initiation of steaming may be automatic upon a single depression of the steam burst button (16). Alternatively a first depression may start the first steam event, and a second depression may start the second steam event. The second steam event may continue for a pre-set period or until a third depression of the steam burst button.