Such hairdryers have handles by which they are grasped by the user. Typically, a hairdryer has a tubular housing terminated with an output aperture blowing hot air in the direction of the output, parallel the tubular housing. The handle generally depends from the housing at some angle with respect to the tubular housing. Often, this is an acute angle on the side of the housing having the output aperture, in the region of about 80°. This is found to be the most convenient compromise, catering both for a self-held hair drying application, for drying the user's own hair, and a third party-held hair drying application, where the user is drying some one else's hair, or indeed, drying (or blowing air at) something other than the user's own head.

Often, when a user dries their own hair, the handle is held in reverse. That is to say, instead of the handle being held such that the output points away from the user's forearm, as one might hold a pistol, the handle is held so that the output points up the user's forearm, or at some acute angle thereto. This enables a more comfortable position to be adopted when drying one's own hair.

Although it makes no reference to it, US-A-4595838 shows a hairdryer that has a loop handle. This enables numerous further holding options to be explored by a user. Thus a back part of the loop handle may be held, with the output pointing backwards or forwards, with either the fingers or the thumb extending through the

loop, or a front part of the handle may be held, again with the output pointing forwards or backwards, and again with the fingers or thumb passing through the loop. That is to say, each handle part offers three positions, a total of six.

Hairdryers also have switches, to control different functions of the hairdryer. A first is the simple on-off function. However, some hairdryers offer numerous other options. For example, there may be different temperature settings available, different airflow settings, ioniser on-off, and cool-shot options. Ionisers inject ions into the airflow to reduce static. Cool shot is used to insert a temporary plug of cool air into the otherwise hot airflow.

A problem occurs that users frequently find it difficult to operate the switches during use, particularly with just the one hand that is holding the hairdryer. As mentioned above, US-A-4595838 discloses a loop handle but the switches that operate the hairdryer are all placed on the front handle. Accordingly, a user holding the rear handle must switch handles to operate a switch, or use there other hand.

Thus it is an object of the present invention to provide a hairdryer that provides multiple holding options and yet facilitates switch usage.

In accordance with the present invention there is provided a hairdryer comprising: a tubular housing having an output at its front adapted to blow air in a first direction; a handle depending from the housing at an angle to said direction;

said handle comprising a front element and a rear element, said front element being nearer the output than said rear element, either element being capable of being held by a user of the hairdryer to manipulate the hairdryer; at least one switch being disposed on the tubular housing between said front and rear elements on each side of the tubular housing adjacent said handle.

Preferably, the handle depends from the housing at an acute angle with respect to the front of the housing, preferably between 65 and 85° thereto, perhaps about 75° thereto.

Thus, whichever handle element is held, and whichever direction the output points with respect to the user, the switch is accessible with either a finger or a thumb of the user. Thus, supposing the hairdryer is held in a user's right hand then, if the front handle is held, with the output pointing forwardly of the user and the user's thumb being between the front and rear elements, the right side switch is inaccessible to the user's fingers (since they point away from between the handle elements). However, the left side switch is accessible to the user's thumb, since it is immediately above the thumb, which can of course be articulated at right angles to the fingers. Alternatively, the thumb could operate the right switch by withdrawing the thumb temporarily from between the handle elements. If the output is now rotated through 180° so that it points backwardly, then either a finger can be employed to operate the left side switch, or still the thumb can be used to operate the right side switch. Finally, if the output is rotated a further 180° so that it is again pointing forwardly, but this time with the user's fingers being between the

handle elements, the right side switch is again inaccessible to the user's fingers, but the left side switch is easily accessible to the user's thumb. In fact, the first position mentioned above is the most awkward for the user to operate one or other of the switches. Be that as it may, that is the one position least likely to be attractive to the user. That is to say, if one wants the hairdryer to blow away from the body (eg drying someone else's hair), one is more likely to hold the rear handle. Likewise, if one wants the hairdryer to blow towards the body (eg drying one's own hair), one is most likely to hold the front handle. In either event, both, switches are each easily accessible to both finger and thumb of the user. The same applies if the user is left-handed, and he or she uses their left hand to hold the hairdryer.

The provision of a switch on each side of the hairdryer is, on the face of it, an expensive solution.

Under consideration are consumer items that are often sold at discounted prices. However, it is a preferred feature of the present invention that, firstly, the hairdryer is provided with several options of air speed and temperature, as well as ioniser and coolshot function. The reason for this is that it is only when there several functions that the requirement to switch between them becomes an issue. Secondly, when there are numerous functions, it is cost-effective to employ a printed circuit board having control elements that are operating at low voltage, even though substantial current may be switched, or in the case of a mains operated hairdryer, mains voltage might also be present on the board. However, for the switching functions, low voltage can be employed. In this instance, inexpensive bubble- type membrane switches can be employed, rather than high

current/high voltage switches that must meet stringent safety requirements. Thus, preferably, said switches comprise low voltage switches, preferably bubble membrane switches. Indeed, said switches may comprise a bubble patch including a plurality of bubble membrane switches each switching a different function.

In one embodiment, said hairdryer is cordless. Our co-pending international patent application number W003/047387 describes a cordless hairdryer having a gas supply burning through a catalyst and an electric motor driven fan providing air flow. A control system is also described that provides various safety and control features. Since the electrical power consumed is relatively minor and the voltage is limited to that of rechargeable batteries, the entire current can be switched through such bubble switches. However, even here, it is preferred that only a low current control voltage is switched, the main current being under the control of on-board circuits.

Preferably, said front and rear handle elements are part of a handle loop. Said loop is connected to the housing at at least one of its ends. In other words, the handle need not necessarily comprise a complete loop, but could be connected to the housing only at a rear connection of the rear element, the front element being connected to the housing only through a connection to the base of the rear handle, or vice versa.

Preferably, the centre of gravity of the hairdryer, when it is in a normal operating position, is arranged to coincide with a line passing between the handle elements and substantially parallel thereto, so that the hairdryer approximately balances on a user's hand engaging the base

of the housing and passing between the handle elements.

This feature renders the hairdryer more balanced for the user, so that, whichever handle element is within the grasp of the user's hand, that element need not be gripped tightly to maintain control of the hairdryer.

A cool shot'is a term of the hair-dressing art.

Hairdryers often provide this function, in which power is momentarily disconnected from the heater element, but the fan continues to blow. Ambient temperature air is then blown, and this has application in some instances.

Normally, a button is provided on the side of the housing that, while held activated, provides the cool shot.

Embodiments of the invention are further described hereinafter, by way of example, with reference to the accompanying drawings, in which: Figure 1 is sided view of a corded, that is to say, mains electrically powered, hairdryer according to the present invention; Figure 2 is an opened side view of a cordless, that is to say, battery and gas powered, hairdryer according to the present invention; Figure 3 shows a control and safety circuit diagram for the hairdryer; Figure 4 is (a) an external side view, (b) a front view and (c) an internal side view, of a handle clamshell, right side, of the hairdryer of Figure 2; and Figure 5 is (a) a plan view and (b) a side view of a membrane switch pad for use on the hairdryer of Figures 2 and 4.

Referring to Figure 1, a hairdryer 10 comprises a housing 12, which consists of two clamshell halves 14a, b, a tubular rear section 16, and a front end nozzle 18. A

handle 504 is formed by the clamshells 141, b. A power cord 312 extends from the base of handle and by means of which mains electrical power is carried to the hairdryer.

The contents of the hairdryer needs little explanation beyond its comprising an on-off switch 402 feeding electrical power to a circuit board (not shown) which in turn feeds power to a motor (not shown) driving a fan (not shown) and to a heating element to heat air blown by the fan.

Figure 2 shows a similar hairdryer 10'also in accordance with the present invention, comprising a housing 12', also consisting of two clamshell halves 14'a, b, a tubular rear section 16', and a front end nozzle 18'.

In Figure 2, the main contents of the hairdryer are visible. In the housing is mounted a motor 20 driving a fan 22. The fan 22 draws air axially through an end aperture 24' (which may be guarded by a grill (not shown) to prevent finger access to the fan 22). The fan 22 expels air radially, but the rear section 16'is shaped so that air exiting the fan 22 is deflected longitudinally along the housing 12'. The arrangement therefore provides a tubular-like flow of air through an air passage 26 defined by the housing 12. Indeed, the motor 20 defines an annular start 26a of the air passage^ 26.

A pair of burners 34 each comprises a gas terminal 38. A gas pipe (not shown) from a gas supply 40, via a supply control mechanism 42 is connectable to the terminal 38.

Combusted gases exit the burners 34 and impinge on a

ceramic block, or pressed steel, baffle 54 to be deflected radially outwardly so as to mix with the tubular air flow caused by the fan 22. The baffle 54 is mounted on a rod 62 connected to a frame 540 mounting the motor 20.

Air heated by the burners 34, and driven by the fan 22, exits a front output aperture 25'of the housing, and can be used for drying hair.

A control circuit 399 and a battery 512 for powering the fan are provided. The control and safety circuit, shown in more detail in Figure 3, control the motor speed, burner level, burner ignition and provide safety shutdown in the case of various failure modes. As the controls and burner are likely to be physically remote, purely mechanical controls and safety features are less desirable. As an electrical power source is available (for the motor), at least part of the gas control system is preferably electrically powered and/or sensed. This provides the most versatile method of control, is the least involved and risky from a development point of view, and allows controls almost identical to a standard corded hairdryer.

Referring to the control and safety circuit block diagram shown as 399 in Figure 3, the rechargeable battery pack 400 supplies all electrical power to the hairdryer. The positive supply from the battery is switched through a mechanical on/off switch 402. In the off position no power is available to energise the normally closed (spring return) solenoid operated gas shut-off valve 404, comprising a reservoir valve.

When the switch 402 is in the on position, the fan

is switched on and the live connection from the battery connects to a vane type airflow switch 406. This consists of a plastic moulded vane and microswitch. When the fan is on and the airflow is above a minimum value the switch 406 closes and the battery supply 400 is connected to the over-temperature thermal switch 408. In an alternative embodiment it is possible to omit the flow switch 406 and rely purely on the over-temperature switch 408 to detect reduced or absent airflow.

The over-temperature thermal switch 408 of any appropriate type, is placed in close proximity to the burner to detect excessive heating for any reason (excessive burner level, restricted airflow, or failure of the fan/motor). If this switch 408 opens due to excessive temperature, power will be disconnected from the solenold valve 404 shutting off the gas supply 414.

The hystereses of this switch 408 should be such that it will not close again until temperature is in the range where the under-temperature switch 416 has opened- preventing the possibility of the gas valve 404 being re- opened as the unit cools down.

The next components in the safety circuit 399 are the under-temperature thermal switch 416 and an override switch 418 connected in parallel. Except when the override switch 418 is held in the ignite position by the user, the under-temperature thermal switch 416 (of any appropriate type) will be open whenever the burner temperature is below a pre-determined value (indicating the burner 410 has not been or is not lit). This removes the supply to the gas control valve 404, switching off the gas supply, if the gas burner 410 is not lit.

Both the over-temperature and under-temperature

switches comprise condition sensors which are provided on the baffle 56 shown in Figure 1.

In order to initially light the burner 410 the override switch 418 is moved to the ignite position which momentarily bypasses the under-temperature switch 416 to provide power to open the gas valve 404. The override switch 418 also provides power to the burner ignition circuit 420 to ignite the gas. As the power supply to an electronic igniter circuit is hardwired through the safety circuit, it is not possible for the igniter circuit to operate unless the switch 418 is in the ignite position.

Once the gas ignites, after a few seconds the under- temperature switch will close and the power supply 400 will remain connected to the solenoid valve 404 after the override switch is released. An opto-isolated monitoring circuit 422 determines whether the under-temperature switch 416 has closed in order to illuminate an LED indicating that the burner has lit. This monitoring circuit 422 has no effect on the safety circuit and is provided purely as an indicator 424 to the user that the gas is lit and they can release the ignite/override switch 418. Failure of this monitoring circuit 422, whilst it may erroneously indicate whether or not the burner is lit, has no effect on the safety shutdown functions of the gas supply.

An alternative approach is to permit a momentary actuation of the igniter switch to maintain gas flow, as well as operation of the ignition mechanism, (described further below) for a fixed short period of time unless the under-temperature switch closes. In that case, burner ignition is indicated and gas flow is maintained

and operation of the ignition mechanism halted. If the burner fails to light, then the gas flow automatically ceases after such period.

In the case where the gas shut-off valve 404 also provides regulation of heat level using for example pulse width modulation of the on/off period of the valve, an opto-isolated signal via isolator 426 for the electronics switches the power on/off to the solenoid valve via isolator 426. Failure of the electronics can never switch on the control valve when the other hardwired safety components indicate a failure condition.

In the case where gas regulation is accomplished using a manual regulator valve 428, the opto isolated control circuit 426 is omitted and the gas solenoid valve 404 is connected directly to the terminals of the under- temperature and override switches 416,418.

However, the former approach is preferred for two reasons. Mechanically variable gas flow regulators are difficult and expensive to manufacture if they are to avoid problems of spitting liquid gas. Much less expensive and currently widely available are on/off valves used in cigarette lighters. By pulsing operation of such valves, shots of gas are released into the conduit upstream of the valve. The burners 34 may include a porous plug (not shown) that also serves as a restrictor so that, even though the pressure upstream of the plug varies during each On-Off cycle, the flow through the restrictor is relatively constant and dependent essentially on the average pressure in the conduit. By varying the On-Off periods, the flow through the restrictor can be adjusted between zero, minimum and maximum flow rates.

Motor control is not critical to the safety of the hairdryer, and therefore can be controlled electronically, as failure leading to overheating is detected by the hardwired over-temperature switch (and airflow switch if necessary). However safety critical components such as the solenoid valve 404 are hardwired using electromechanical components. Furthermore the HT supply 430 to the igniter 420, and the connection to the solenoid valve are electrically opto-isolated via respective isolations of any appropriate type 432,426 in the electronic control circuit 434.

According to this arrangement, the safety critical circuits cannot be compromised by failure of the electronics. The use of optical isolation components to prevent any monitoring or control circuits of the electronics providing power or incorrectly enabling part of the safety circuit ensure this. Failure of the electronic control circuits may prevent operation of the hairdryer, but always in a fail-safe manner.

The safety circuit shuts off the gas supply in the event of failure to ignite the gas burner (or subsequent extinguishing of the burner, either controlled or due to a failure), an over-temperature condition (due to failure of the fan/motor, blockage of airflow etc. ) or airflow less than a minimum level.

As regards motor control and electronic gas regulation, there are two embodiments presented regarding the gas regulation (to provide different heat settings).

One uses a manual regulator valve 428 to provide variable heat control and the other modulates the on/off period of the gas shutoff valve to control the average gas flow.

The advantage of the electronic control of the solenoid valve is the reduction of mechanical parts (albeit at the increase of electronic control) and more freedom in the mounting position and type of controls.

The electronic control circuit (ECC) 434 which is preferably a printed circuit board provides, in addition to the possible PWM control of the solenoid valve; PWM speed control of the fan motor 42, igniter circuit 420, if desired, battery monitoring circuit and low battery display LED 436, burner lit monitoring and display LED 424, mounting platform for on/off/ignition switch, mounting platform for burner and motor control switches 438,440, and mounting platform for gas solenoid valve 404 and a"junction box"for electrical cabling.

Turning the manual switch 402 to its"on"position provides power to the electronics and motor control circuits.

The on/off switch 402 has a third, momentary spring loaded position in which it operates igniter 420. This is the"ignition"position where the user must hold the switch to ignite the gas. Moving the switch to this position opens the gas valve and turns on the HT spark igniter 420.

However, these initial controls are then normally untouched until it is desired to switch the hairdryer off. However, it is desirable to be able to control the heat or power of the air blown. For this a membrane patch 602 (see Figurel and 5) is provided on each side of the body 12, comprising a number of button switches 430,438 and 440, and LED lights 442,444, and 446. Thus,

once the burner has lit, a temperature sensor detects this, and one LED lamp 446 lights to indicate gas lit.

The user may release the switch 402 back to the"on" position.

The fan will run at the speed selected by the"fan speed"control switch 440. This could be a 2 position switch giving two fan speeds, or a number of speed settings. The gas may still be still turned off at this point. LED 442 may indicate low battery condition and/or recharging, if the batteries are on-board during charging.

The heat level is controlled by switch 438 giving two heat levels or a number of heat settings. Indeed, it may be that the more the switch is held on, or repeatedly toggled, the more the desired heat level is registered.

A"cool shot"option is also possible involving extinguishing and re-igniting the burner. Cold air operation is possible by switching the unit to"off", then moving the switch to"on"without igniting the gas.

However, a preferred arrangement is to provide third operator switch 430 on patch 602 and operational in the circuit arrangement 399. In this, the gas flow is simply regulated to flow at a minimum level sufficient to keep the gas combustion going so that it can subsequently be raised again once the cool shot switch 430 is released, but at such a low level that the temperature rise of the air flowing through the hairdryer is minimal compared to normal. This more precisely mimics the traditional approach to cool shots and minimises operator actions to effect and cease the cool shot function. In this approach, it may be necessary to disable the under-

temperature sensor switch while the cool shot is operating. Since minimal gas flows during this period, in any event, there is little or no danger. Moreover, the cool shot switch 430 one which is biased to its off position. Alternatively, it may simply be a toggle on- off switch. LED 444 may operate when the coolshot mode is employed.

Ionisers are an increasingly common feature of hairdryers, and a fourth switch might be provided for that (only shown generally in Figure 1).

Figures 4 a to c show one 504 of the two clamshells 14'a, b in detail, with mating screw holes and bosses506.

The rear 510 of the handle is open for connection and disconnection of the rechargeable battery pack 512 (not shown in Figure 4). In Figure 1 the batteries are shown at 512 as an integral assembly with the printed control circuit board 399. This is an option, but a removable battery pack (not shown) means that no waiting time is required while the battery is recharged, assuming a spare battery pack is employed. In this event, the PCB is disposed in cavity 514 in the handle clamshell 504.

The electrical consumption of the hairdryer is very small. Accordingly the simplest electrical switching is adequate. What minimal current is taken is by the fan motor, which is switched externally only by the primary On-Off switch 402. In this embodiment, a simple toggle microswitch (not shown) is provided, and this is pivoted between the clamshells about hinge bushes 598 at the rear of the handle. However, even smaller current is employed by the control circuit to switch between fan power settings, heat control settings, and the cool shot function. The bubble-membrane type switches 430,438, 440

are mounted on a self-adhesive pad 602 adhered to a switch pad area 600 on each clamshell. A connection strip 604 extends through slots 606 in the clamshells to connect with the PCB. Because they are inexpensive, each switch is duplicated, one on either side of the hairdryer so that they are easily manipulated by finger or thumb whichever part of the handle is grasped by either hand of the user, and in whichever direction the hairdryer is pointed.

Returning to Figure 1, the patch 602 is disposed above the handle 504. One is provided on each side of the body. In front of the patch 602 is disposed a liquid crystal display 648 which can be employed to display air temperature, blow speed setting and/or cool shot and/or ioniser functions. This might only be provided on one side of the body, since it is not a problem to manipulate the hairdryer when held to look at either side of it; this is different to manipulating switches with the hand that is also holding the handle.

The handle 504 is in the form of a loop providing front 504a and rear 504b handle elements, with a handle aperture 505. Each element 504a, b is thus both connected to each other (504c) and to the housing body 12 (504d, e).

However, not all those connections are necessary, even if preferred. For example, two separate handles could be provided without joint 504c. However, this would potentially deprive the hairdryer of the benefit of being able to be hung from hooks by means of the loop 505.

Also communications between the handle elements might be difficult. Likewise, one of connections 504d or e could be omitted, although omitting connection 504e from the rear handle might also be difficult with regard to electrical connections.

It is to be noted that rear handle 504b of the corded hairdryer 10 of Figure 1 can be thinner that the handle of cordless hairdryer 10'of Figure 2, because the latter houses batteries that are not needed in the corded version.

In either event, however, the handle 504 has an axis 29 which is disposed at an angle a with respect to the axis 23 of the body 12 (which axis is also parallel the direction of air output from output 25 of the hairdryer).

A is arranged to be about 80°, but can be any convenient angle.

However, the region of the loop 505 between the connections 504d, e is preferably arranged to coincide approximately with a line 27 substantially at right angles to the direction 23 of air output and passing through the centre of gravity cg of the hairdryer. In this way, the hairdryer can be balanced on a user's hand passing through the loop 505 without the need to grasp tightly one or other of the handles. This is beneficial for comfortable use, but particularly assists when one finger or thumb is used to manipulate on or other of the switch pads 602. In broad terms, the line. 27 may be considered substantially parallel the line 29.

While the centre of gravity may move, depending on whether the hairdryer is corded or cordless, the principle described above remains the same. Indeed, it is particularly important in relation to the cordless version which is heavier than the corded version by virtue of the batteries and gas canisters. However, as is evident from Figure 1, the gas canister 40 (in Figure 2) is on one side of the aforementioned line 27, while

the batteries 512 are on the other side. Consequently, in this respect, there is little design change needed between corded and cordless versions.

It will be appreciated that features and components from the various embodiments can be combined or interchanged as appropriate without departing from the inventive concept. The individual components described, to the extent they are generic or off-the-shelf products, will be well known to the skilled reader and hence have not been described in detail.