U.S. patent application number 15/552231 was filed with the patent office on 2018-02-08 for hair styling appliance.
The applicant listed for this patent is Jemella Limited. Invention is credited to Mark Andrew GAGIANO, Timothy David MOORE, Robert Alexander WEATHERLY.
Application Number | 20180035776 15/552231 |
Document ID | / |
Family ID | 52821842 |
Filed Date | 2018-02-08 |
United States Patent
Application |
20180035776 |
Kind Code |
A1 |
WEATHERLY; Robert Alexander ;
et al. |
February 8, 2018 |
HAIR STYLING APPLIANCE
Abstract
A hair styling apparatus includes a plurality of heater
electrodes which heat one or more hair styling heaters, a power
source for powering the plurality of heater electrodes and a
controller configured to control powering of the plurality of
heater electrodes from the power source. The plurality of heaters
includes a first subset and a second subset of heaters. The
controller is configured to, in a first mode of operation; control
the power source so that the first and second subsets are not
simultaneously powered.
Inventors: |
WEATHERLY; Robert Alexander;
(Hinxton, GB) ; GAGIANO; Mark Andrew; (Piara
Waters, AU) ; MOORE; Timothy David; (Royston
Hertfordshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jemella Limited |
Leeds Yorkshire |
|
GB |
|
|
Family ID: |
52821842 |
Appl. No.: |
15/552231 |
Filed: |
February 16, 2016 |
PCT Filed: |
February 16, 2016 |
PCT NO: |
PCT/GB2016/050382 |
371 Date: |
August 18, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A45D 2/001 20130101;
A45D 1/06 20130101; A45D 1/28 20130101; A45D 1/14 20130101 |
International
Class: |
A45D 1/14 20060101
A45D001/14; A45D 1/28 20060101 A45D001/28; A45D 2/00 20060101
A45D002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 2015 |
GB |
1502763.4 |
Claims
1. A hair styling apparatus comprising: a plurality of heater
electrodes which heat one or more hair styling heaters, the
plurality of heater electrodes comprising a first subset and a
second subset; a power source for powering the plurality of heater
electrodes and a controller configured to control powering of the
plurality of heater electrodes from the power source; wherein, in a
first mode of operation, the controller is configured to control
the power source so that the first and second subsets of the
plurality of heater electrodes are not simultaneously powered and
are powered in a time interleaved manner multiple times per
second.
2. (canceled)
3. A hair styling apparatus according to claim 1, wherein the
controller is configured to select the first and second subsets so
that a total current drawn by each of the first and second subsets
is below a predetermined current threshold.
4. A hair styling apparatus according to claim 1, wherein no heater
electrodes are selected for both the first and second sub sets.
5. A hair styling apparatus according to claim 4, wherein the
controller is configured to switch the power source between the
first and second subsets.
6. A hair styling apparatus according to claim 5, wherein the
controller is configured to switch between each subset multiple
times per second.
7. A hair styling apparatus according to claim 1, wherein the
controller is configured to alternate between the first mode of
operation and a second mode of operation in which the first and
second subsets of the plurality of heater electrodes are
simultaneously powered.
8. A hair styling apparatus according to claim 7, wherein the
controller is configured to switch from the second mode of
operation to the first mode of operation in response to a control
signal.
9. A hair styling apparatus according to claim 8, wherein the
control signal is that a predetermined amount of time in the second
mode of operation has elapsed.
10. A hair styling apparatus according to claim 7, wherein the
power source is a battery source and the hair styling apparatus
further comprises a battery temperature sensor which senses the
temperature of the battery source and which sends a battery
temperature sense signal to the controller.
11. A hair styling apparatus according to claim 10, wherein the
battery temperature sense signal is compared to a battery
temperature threshold and the control signal is generated when the
battery temperature sense signal is greater than the battery
temperature threshold.
12. A hair styling apparatus according to claim 11, wherein the
battery temperature threshold is in the range of 60 to 80 degrees
C., more preferably 70 degrees C.
13. A hair styling apparatus according to claim 7, further
comprising a temperature sensor sensing ambient temperature; and
said control signal is generated when the sensed ambient
temperature is below a threshold ambient temperature.
14. A hair styling apparatus according to claim 13, wherein the
ambient temperature threshold is in the range of 25-35 degrees
C.
15. A hair styling apparatus according to claim 1, comprising a
first arm having a first contacting surface and a second arm having
a second contacting surface, wherein the arms are moveable between
a closed position in which the first and second contacting surfaces
are adjacent and an open position in which the first and second
contacting surfaces are spaced apart.
16. A hair styling apparatus according to claim 15, wherein the
first arm comprises a first hair styling heater having a plurality
of heater electrodes.
17. A hair styling apparatus according to claim 15, wherein the
first arm comprises a first hair styling heater and the second arm
comprises a second hair styling heater and each hair styling heater
comprises at least one heater electrode.
18. A hair styling apparatus according to claim 1, comprising a
touch sensitive switch configured to enable or disable the hair
styling apparatus.
19. A hair styling apparatus according to claim 18, comprising a
first arm having a first contacting surface and a second arm having
a second contacting surface, wherein the arms are moveable between
a closed position in which the first and second contacting surfaces
are adjacent and an open position in which the first and second
contacting surfaces are spaced apart, wherein the touch sensitive
switch is located on the first or second contacting surface.
20. A hair styling apparatus according to claim 18, wherein when
the arms are in the closed position, the touch sensitive switch is
deactivated.
21. A hair styling apparatus according to claim 18, wherein the
controller is configured to determine when a user has activated
said touch sensitive switch for at least a predetermined duration
of time and enable or disable the hair styling apparatus responsive
to said determining.
22. A hair styling apparatus according to claim 1, wherein the or
each heater comprises a heater plate which is mounted on a
thermally insulating support structure.
23. A hair styling apparatus according to claim 22, wherein the
heater plate comprises at least one recess which cooperates with a
corresponding projection on the thermally insulating support
structure.
24. A hair styling apparatus according to claim 22, wherein the
thermally insulating support structure is resiliently mounted
within an arm of the hair styling apparatus.
25. A hair styling apparatus according to claim 1, wherein the
power source is a battery source.
26. A hair styling apparatus according to claim 1, wherein, in the
first mode of operation, the controller is configured to control
the powering of the heater electrodes using predefined heating
cycles during one or more of which power is provided, at different
times, to the first and second subsets of the plurality of heaters,
and preferably wherein the heating cycles have a duration of
between 100 .mu.s and 500 ms.
27. A hair styling apparatus according to claim 1, wherein the
controller is configured to use pulse width modulation, (PWM),
power control to control the delivery of power to the first and
second subsets such that, during the first mode of operation, the
controller is configured to generate power control signals for the
first and second subsets to cause power to be delivered to the
first and second subsets at different times within each of one or
more heating cycles of the PWM power control.
28. A method of controlling a hair styling apparatus comprising a
plurality of heater electrodes which heat one or more hair styling
heaters, the plurality of heaters comprising a first subset and a
second subset; the method comprising: controlling powering of the
heater electrodes so that the first and second subsets of the
plurality of heaters are not simultaneously powered and are powered
in a time interleaved manner multiple times per second.
29. A controller for a hair styling appliance, wherein the
controller configured is configured to implement the method of
claim 28.
Description
FIELD OF THE INVENTION
[0001] This invention relates to hair styling appliances, in
particular low voltage, for example battery operated devices.
BACKGROUND TO THE INVENTION
[0002] There are a variety of apparatus available for styling hair.
One form of apparatus is known as a straightener which employs
plates that are heatable. To style, hair is clamped between the
plates and heated above a transition temperature where it becomes
mouldable. Depending on the type, thickness, condition and quantity
of hair, the transition temperature may be in the range of
160-200.degree. C.
[0003] A hair styling appliance can be employed to straighten, curl
and/or crimp hair.
[0004] The temperature range required, user expectations with
regard to the time to heat-up, thermal control, and other factors
combine to drive existing hair styling appliances to employ mains
power for the heater(s).
[0005] In WO2014/001769 and GB2503521 to the present applicant, a
hair styling appliance including a battery power source for at
least one heater is taught.
[0006] The inventors have realised that further improvement in the
use of a battery power source is possible.
SUMMARY OF THE INVENTION
[0007] According to a first aspect of the invention, there is
provided a hair styling apparatus comprising: a plurality of heater
electrodes which heat one or more hair styling heaters, the
plurality of heaters comprising a first subset and a second subset;
a power source for powering the plurality of heater electrodes and
a controller configured to control powering of the plurality of
heater electrodes from the power source, wherein, in a first mode
of operation, the controller is configured to control the power
source so that the first and second subsets of the plurality of
heaters are not simultaneously powered. The power source may be a
battery source. Alternatively, the power source may be mains
power.
[0008] Typically, in this first mode of operation, the controller
controls power delivery so that power is delivered to the first and
second subsets in a time interleaved manner, preferably multiple
times per second. Interleaving the power delivery in this way
offers a number of advantages. For example, if the first subset of
heater electrodes is associated with a first hair styling heater
and the second subset of heater electrodes is associated with a
second hair styling heater, then the controller can control the
heating of the first and second hair styling heaters so that they
are both heated, at the same time, to respective desired operating
temperatures (which may be the same). Similarly, if the first and
second subsets of heater electrodes are associated with different
parts of one hair styling heater then the controller can control
the heating of the different parts of the heater so that they are
both heated, at the same time, to a desired operating temperature.
This is possible as such hair styling heaters (and other kinds of
heaters) normally have a relatively high thermal inertia so that
they do not cool down quickly once power is removed from the heater
electrodes.
[0009] Interleaving of the driving of the electrodes in this manner
also reduces the current drawn from the power source. When the
power source is a battery, reducing the current draw is important
as this reduces the energy lost in the internal resistance of the
battery: P=I.sup.2R, where I is the current drawn and R is the
internal resistance. Hence operating in this first mode of
operation provides the most efficient heating of the heaters. Of
course, in other modes of operation heaters from the first and
second subsets may be powered simultaneously, for example, if the
load is very high.
[0010] The controller may be configured to select the first and
second subsets so that a total current drawn by each of the first
and second subsets is below a predetermined current threshold. This
is particularly useful for a battery power source because keeping
the current draw below the threshold may prevent the battery from
overheating (due to the above described I.sup.2R losses). The
predetermined current threshold may be equivalent to a multiple
(e.g. 1.5) of the current draw for a single heater electrode.
[0011] In other words, the controller is configured to control
powering of the heater electrodes from the power source. The first
mode of operation of the controller (there may only be the one
mode) comprises limiting the total number of heater electrodes that
may be simultaneously powered such that a predetermined current
limit is not exceeded. The fact a current limit is imposed means
that the controller is configured to prevent all the heater
electrodes being powered at the same time. This current limit may
be deemed a nominal current draw.
[0012] The plurality of heater electrodes may be divided into
discrete subsets. Thus no heater electrodes are in both the first
and second subsets. Alternatively, the first and second subsets may
have some (but not all) heater electrodes in common. It will be
appreciated that there may be more than two subsets of electrodes,
e.g. three or even four, depending on the overall number of heater
electrodes within the apparatus. Each subset may comprise one or
more electrodes.
[0013] The controller may be configured to switch the power source
between the first and second subsets, for example multiple times
per second. This may be done, for example, to maintain the heater
at a desired operating temperature. The controller may comprise a
heating cycle in which it cycles through all of the subsets of
powerable heater electrodes, determining if power may need to be
applied. If not, the controller may opt to retain power to the
currently powered subset, switch to another, or opt to power none
of the heater electrodes if heater plates (or zones on a heater
plate) are at a preferred operating temperature. The switching
frequency between each subset may be in the order of tens, hundreds
or thousands of cycles per second. Typically the heating cycle will
have a period of between 100 .mu.s and 500 ms. The first and second
subsets may be powered in anti-phase, i.e. one subset is off when
the other subset is on. In such anti-phase operation there may
however be periods in which none of the electrodes are powered.
[0014] The controller may be configured to alternate between the
first mode of operation and a second mode of operation in which the
first and second subsets of the plurality of heater electrodes are
simultaneously powered. For example, simultaneous heating may take
place during the initial heat up from power on. In this second mode
of operation, the nominal current draw is exceeded temporarily.
When operating in this second mode, the controller may switch the
power to both subsets of heater electrodes such that there are: 1)
overlapping periods in which power is simultaneously supplied to
heater electrodes in the first and second subsets; 2) periods in
which power is supplied to heater electrodes of just one of the
first and second subsets; and 3) periods in which no power is
supplied to heater electrodes of the first and second subsets. The
controller may control the duration of the overlapping periods so
that they reduce with time from, for example, an initial switching
on time. The controller may reduce the duration of the overlap
either in response to a sensed condition or based on pre-stored
data defining the switching sequence.
[0015] The controller may be configured to switch from the second
mode of operation to the first mode of operation in response to a
control signal. The control signal may be that a predetermined
amount of time in the second mode of operation has elapsed. The
predetermined amount of time may be based on predetermined
characteristics of the battery power source and may be a few
seconds. The controller may then continue to operate in the first
mode of operation for a further period of time (for example 30
seconds or more) after which periods of operating in the second
mode may be possible.
[0016] Where the power source is a battery source, the hair styling
apparatus may further comprise a battery temperature sensor which
senses the temperature of the battery source and which sends a
battery temperature sense signal to the controller. In some
embodiments a battery temperature sensor may be integrated into the
hair styling apparatus, however in other embodiments the battery
power source may comprise an integrated temperature sensor having a
connection coupleable to the battery temperature sense input.
[0017] The battery temperature sense signal may be compared to a
battery temperature threshold and the control signal may be
generated by the controller or at the sensor when the battery
temperature sense signal is greater than the battery temperature
threshold. Alternatively, the control signal may be generated when
the battery temperature is increasing at a rate such that a
threshold value is predicted to be exceeded. The battery
temperature threshold may be in the range of 60 to 80 degrees C.,
more preferably 70 degrees C.
[0018] There may also be temperature sensor sensing ambient
temperature. Said control signal may be generated by the controller
or the sensor when the sensed ambient temperature is below a
threshold ambient temperature. The ambient temperature threshold
may be in the range of 25-35 degrees C., more preferably 25 or 33
degrees C.
[0019] In other words, the controller may be configured to limit a
duration in which the subsets of heater electrodes are
simultaneously powerable by the power source. This may also be
dependent on the battery temperature or ambient temperature.
[0020] The hair styling apparatus may comprise a first arm having a
first contacting surface and a second arm having a second
contacting surface, wherein the arms are moveable between a closed
position in which the first and second contacting surfaces are
adjacent and an open position in which the first and second
contacting surfaces are spaced apart. The first arm may comprise a
first hair styling heater having a plurality of heater electrodes.
The first arm comprises a first hair styling heater and the second
arm comprises a second hair styling heater and each hair styling
heater comprises at least one heater electrode. In this
arrangement, the plurality of electrodes comprises at least one on
each arm. A plurality of electrodes includes two electrodes. Where
there are only two electrodes, e.g. one on each arm or a single
heater with two electrodes, the first subset may comprise the first
electrode and the second subset may comprise the second
electrode.
[0021] The hair styling apparatus may further comprise a touch
sensitive switch configured to enable or disable the hair styling
apparatus. It will be appreciated that the touch sensitive switch
can be used on its own as a separate invention as well as in
conjunction with the different powering modes of operation.
[0022] For an apparatus having a pair of arms as described above,
the touch sensitive switch may be located on the first or second
contacting surface. When the arms are in the closed position, the
touch sensitive switch may be deactivated to prevent unintended
activation of the switch. In use, a user may activate the touch
sensitive switch by pressing on or otherwise contacting said touch
sensitive switch for at least a predetermined duration of time.
This activation may be determined by the switch or the controller
and the controller may enable or disable the hair styling apparatus
responsive to said determining.
[0023] The or each heater may comprise a heater plate which is
mounted on a thermally insulating support structure. It will be
appreciated that the thermally insulating support structure can be
used on its own as a separate invention as well as in conjunction
with the different powering modes of operation and/or touch
sensitive switch.
[0024] The heater plate may comprise at least one recess which
cooperates with a corresponding projection on the thermally
insulating support structure. The recess and projection may be
L-shaped. Other mechanisms for mounting the heater plate on the
support may be used. The thermally insulating support structure may
be resiliently mounted within an arm of the hair styling apparatus.
For example, a spring mechanism may be used. Such a resilient
mounting allows the heater plate to move relative to the casing of
the arm during styling, allowing the plates to retain contact with
varying thicknesses and changes in the profile of hair clamped
between opposing pairs of styling surfaces on the heater
plates.
[0025] According to another aspect of the invention there is
provided a method of controlling a hair styling apparatus
comprising a plurality of heater electrodes which heat one or more
hair styling heaters, the plurality of heaters comprising a first
subset and a second subset; the method comprising: controlling
powering of the heater electrodes so that the first and second
subsets of the plurality of heaters are not simultaneously
powered.
[0026] According to another aspect of the invention there is
provided a controller for a hair styling appliance, wherein the
controller configured is configured to implement the method
described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] These and other aspects of the invention will now be further
described, by way of example only, with reference to the
accompanying figures in which:
[0028] FIG. 1 shows a first example of a hair styling appliance in
which embodiments of the invention may be employed;
[0029] FIG. 2 shows a schematic block diagram of a hair styling
appliance of the type illustrated in FIG. 1;
[0030] FIG. 3 shows a plan view of an embodiment of a hair styling
heater for use in the hair styling appliance of FIG. 1;
[0031] FIGS. 4a and 4b show timing diagrams illustrating example
duty cycles of heating electrodes driven, for example, by the
control system in FIG. 2;
[0032] FIG. 5 shows a variant of the schematic block diagram of
FIG. 2;
[0033] FIGS. 6a to 6d show timing diagrams illustrating example
duty cycles of heating electrodes driven, for example, by the
control system in FIG. 5; and
[0034] FIG. 7 shows a cross sectional view of the hair styling
appliance.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] FIG. 1 depicts an example of a typical hair straightener 1.
The hair straightener 1 includes first and second arms each
comprising an arm member 4a, 4b and heatable plates 6a, 6b coupled
to heaters (not shown) in thermal contact with the heatable plates.
The heatable plates are substantially flat and are arranged on the
inside surfaces of the arms in an opposing formation. During the
straightening process, hair is clamped between the hot heatable
plates and then pulled under tension through the plates so as to
mould it into a straightened form. The hair straightener may also
be used to curl hair by rotating the hair straightener 180.degree.
towards the head prior to pulling the hair through the hot heatable
plates.
[0036] Also shown in FIG. 1 is touch sensitive switch 5070 which is
used to power the hair styling appliance on and off. The switch may
be implemented as a capacitive touch switch comprising an electrode
placed behind the plastic casing of the hair styling appliance.
This obviates the need for a mechanical switch. In variants a
resistive touch sensitive switch may also be used, or a piezo touch
switch. As shown in FIG. 1, the touch sensitive switch 5070 is
positioned on the inside of an arm facing the other arm. This means
that the switch can only be pressed when the arms are spaced apart
to prevent a user accidentally touching the switch and
unintentionally turning the hair styling appliance on. Further,
should the hair styling appliance be placed in luggage, such as a
handbag, if a user rummages around in the bag for an item, it also
prevents any accidental pressing of the switch. As a further safety
mechanism, in embodiments the switch may also be deactivated (or
the power supply configured to prevent activation of the appliance)
when the arms of the hair styling appliance are closed
together.
[0037] It will be appreciated that a hair straightener is just one
example of a hair styling appliance and a skilled person would
implement the various embodiments of the invention without
difficult into other hair styling appliances such as a "crimping
iron" for crimping hair or a hair styling appliance for curling
hair.
[0038] FIG. 2 shows a block diagram of a power/control system 500
for a hair styling appliance incorporating a heater 300. The system
comprises a low voltage power supply 504 deriving power from a 12v
lithium ion battery 505 and/or a mains power supply input 502,
which is used to charge the battery 505 via an AC to DC converter
503 which may be external or internal to the appliance. Power
supply 504 may be configured to provide approximately 100 watts per
heater; the heater resistance when hot may be selected
accordingly--for example at 12v a current in the range 5-10 amps
may be delivered to a heater with a resistance in the range 1-2
ohms. The resistance may be scaled accordingly as the design
voltage increases or decreases (changing as the inverse square of
the voltage).
[0039] Power from power supply 504 is provided to a power control
module 514, which in turn powers the one or more heaters 516. Power
control module 514 may employ one or more power semiconductor
switching devices to provide pulse width modulation control of the
(DC) voltage from power supply 504 to heaters 516. Thus a high
percentage on-time duty cycle may be employed during the initial,
heating phase and afterwards the on-time duty cycle may be reduced
and controlled to control the temperature(s) of the heaters
516.
[0040] Power from power supply 504 is also provided to a
microcontroller/control means 506 coupled to non-volatile memory
508 storing processor control code for a temperature control
algorithm, and to RAM 510. The skilled person will appreciate that
any of a wide range of different control algorithms may be employed
including, but not limited to, on-off control and proportional
control. Optionally the control loop may include a feed-forward
element responsive to a further input parameter relating to the
hair styling appliance, for example to use the operation of the
apparatus to improve the temperature control. An optional user
interface 512 is also coupled to microcontroller 506, for example
to provide one or more user controls and/or output indications such
as a light or audible alert. The output(s) may be employed to
indicate, for example, when the temperature of the heating plate
has reached an operating temperature, for example in a region
140.degree. C.-185.degree. C.
[0041] Microcontroller 506 is also coupled to one or more optional
temperature sensors such as thermistors 340. However, as previously
mentioned, the temperature of a heating element may be sensed from
its resistance and thus embodiments of the system include a current
sense input 515 to microcontroller 506 sensing the current provided
to a heater, for example via a current-sense resistor connected in
series with the electrode. A predetermined calibration of
resistance against temperature for an electrode may be stored in
non-volatile memory 504 and in this way the printed track may be
employed as a temperature sensor.
[0042] In the illustrative embodiment of FIG. 2, the touch
sensitive switch 5070 is shown coupled to the low voltage PSU 504
to remove the need for the microcontroller to be permanently
powered up. When off, the low voltage PSU 504 monitors for a change
in capacitance of the touch sensitive switch indicating that a user
has pressed the switch. The low voltage PSU then powers up the hair
styling appliance. When on, the low voltage PSU 504 again monitors
for a change in capacitance of the switch, then powering down the
hair styling appliance. To power up and down, it may be necessary
for a user to press on the touch sensitive switch for a minimum
period of time before the PSU fully registers the press as a valid
request to power on/off. This eliminates any accidental power up,
or when styling, any accidental touching of the touch sensitive
switch. A user may, for example, be required to press the touch
sensitive switch for two, three, four or five seconds, or longer.
In variants two touch sensitive switches may be used: one for
turning the styling appliance on, another for turning the styling
appliance off.
[0043] Providing such a touch sensitive switch on a hair styling
appliance provides several advantages. Firstly, for battery powered
products, if the hair styling appliance is carried around in
luggage, it prevents the appliance being accidentally knocked on by
other items in the luggage. Further, it also improves the aesthetic
appearance of the product, eliminating the need for additional
components on the surface of the hair styling appliance.
[0044] In this embodiment the touch sensitive switch is shown
coupled to the low voltage PSU. In variants such a switch may be
coupled to the microcontroller, although in such variants it will
then be appreciated that the microcontroller may then need to be
permanently powered to permit detection of a press of the touch
sensitive switch. In other variants a dedicated circuit may also be
used.
[0045] This touch sensitive power switch may be applied to any of
the embodiments described herein and also as an adaption to
otherwise standard devices.
[0046] Each heater plate may be powered by a heater electrode.
Depending upon the thickness of the heater plate, lateral
conductivity within the plate may not be sufficient to give the
desired results with a single heater electrode. Accordingly, an
example of a heater plate is illustrated in FIG. 3 which may form
the heatable plates 6a, 6b of the hair straightener of FIG. 1. The
heater plate 300 may be provided with a plurality of separately
controllable heating zones 300a, b, each with a respective
electrode 330a, b and thermistor 340a, b. Connections to these are
brought out, for convenience, to one edge of the heater plate; a
broadened track region 332 is provided for the electrode further
from the connection point to reduce heating in the connection path.
Each of the electrodes is provided with a separate control loop
controlled by the temperature sensed by the respective thermistor.
In embodiments more than 3 zones may be provided.
[0047] The heater used in the various embodiments described herein
may be formed as described in WO2014/001769 and GB2503521 which are
incorporated by reference. Thus, the heater may comprise an
aluminium heater plate of thickness of order 1 mm, bearing a plasma
electrolytic oxide (PEO) coating of aluminium oxide of thickness
less than 100 .mu.m, for example in the range 5-15 .mu.m.
[0048] The hair styling appliance comprises a plurality of
electrodes. As shown in FIG. 1, there may two heater plates, each
with their own electrode and thus there are two electrodes.
Alternatively, only one arm of the appliance shown in FIG. 1 may
comprise a heater plate but this heater plate comprises at least
two, possibly more electrodes. There may also be multiple heater
plates each having multiple electrodes.
[0049] The power to the plurality of heater electrodes may be
independently controlled. For example, for an appliance having two
arms, each with a heater and one heater electrode for each heater,
FIGS. 4a and 4b show the Voltage against Time for each heater
electrode. In this example illustration, the microcontroller 506
uses pulse width modulation (PWM) power control to control the
supply of power to the two heater electrodes using the power
control block 514. In pulse width modulation power control, the "on
time" of the power signal within a sequence of PWM periods (here
labelled `d` and also referred to in other parts of this document
as heater cycles) is varied in order to vary the amount of power
delivered to each heater electrode. Typically, the PWM period /
heater cycle may be between 100 .mu.s and 500 ms. It will be
observed from FIGS. 4a and 4b that initially both heater electrodes
are powered simultaneously until the desired operating temperature
is reached. A high percentage on-time duty cycle within any given
period `d` may be employed during the initial heating phase;
afterwards the on-time duty cycle may be reduced for each heater so
as to retain the hair styling heater at a desired operating
temperature. Each heater may be controlled independently to
stabilise the temperature of each heater at the desired operating
temperature. Accordingly, the draw is not exactly the same for both
heater electrodes. Nevertheless, it can be observed from FIGS. 4a
and 4b that there may be sustained periods of a maximum current
draw as a result of both heaters being powered simultaneously.
[0050] When powered by battery, a high current draw, such as from
driving both heaters simultaneously, may lead to the battery power
source heating up to an unacceptably high temperature. This may be
exacerbated if both heaters are simultaneously driven for extended
periods of time. The current draw when simultaneously driving the
heaters, combined with a desire to conceal the battery power source
means that heat dissipation may become an important factor in the
construction of such a hair styling appliance.
[0051] FIG. 5 shows a variant of the schematic block diagram of
FIG. 2 with modified microcontroller/control means and power
control module 514b. The reference numbers in common are used in
both systems and thus any description applies equally to both.
[0052] The microcontroller switching control signal 708, labelled
`temp/power control` in FIG. 5 may comprise multiple outputs, one
for each heater power switch to be controlled. The embodiment shown
in FIG. 5 comprises two heater electrodes, one on each of the two
heater plates. Two outputs, one to activate the first heater
electrode via the first power switch 702 and the second to activate
the second heater electrode via the second power switch 704 are
present on the power control module. In FIG. 5, further heater
electrodes may also be driven. These may be present, for example,
in a multi-zoned heater variant. Dotted arrow lines to the heaters
516 show optional connections to such additional heater
elements.
[0053] In variants the switching control signal may be a serial
data connection or encoded such that the control system can scale
to independently control multiple heater elements. This may be
particularly useful in embodiments having multiple heating zones
(two or three per heater for example) and where the number of
outputs from the microcontroller may be limited. Alternatively the
microcontroller may have multiple outputs, one for each power
switch. The optional decode block 706 in the power control module
514b decodes the signal received from the microcontroller and
splits this out into separate drive signals to activate the power
switches 702 and 704. In variants incorporating multiple heating
zones on each heater plate the signal may be decoded into more
outputs, one for each zone.
[0054] Battery power source 505 in FIG. 5 may further incorporate a
battery temperature sensor 5050, such as a thermistor. The battery
temperature sensor 5050 provides a battery temperature sense signal
5051 coupled to the microcontroller 506. The battery temperature
sense signal may be factored into the temperature control algorithm
and powering of the heater plates. It will be appreciated however
that such a feature is optional.
[0055] In the embodiment shown in FIG. 5, the battery temperature
sensor many also be used as part of the safety shutdown 520. As set
out above, the styling appliance may incorporate one or more safety
shut down circuits 520 coupled to the one or more heater electrodes
and/or temperature sensors 340 to monitor the heater temperature
and electronically shut down the power supply to the heater should
overheating be detected. In embodiments, this may be extended to
also prevent overheating of the battery. In embodiments safety shut
down circuit 520 controls a guard transistor 522, as illustrated a
power MOSFET, which removes power from the power control block on
detection of a potential fault. Guard transistor 522 may be
provided either before or after power control block 514a. In normal
operation this device is always on; the device may be selected such
that when power is removed from the transistor it switches off,
thus failing safe, for example by employing an enhancement-mode
device. Such control and safety shut down is applicable to all the
embodiments described herein.
[0056] The battery temperature sensor 5050 (or another battery
temperature sensor) may additionally or alternatively be used to
control power on/off of the hair styling appliance. The generated
signal B.sub.Tsense 5051 is fed into the microcontroller 506 and
may be used to provide battery temperature information for use in a
safety mechanism to shut down the styling appliance, or stop power
delivery to one or more heater elements/plates if the battery
temperature exceeds a battery threshold temperature. Thus, the
microcontroller/control means may be arranged such that power is
only supplied to the heating elements/plates when the temperature
sensed by the battery temperature sensor is below a battery
threshold temperature. In embodiments, this threshold temperature
may be a value in the range of 60-100.degree. C., for example
70.degree. C. However it will be appreciated that the operational
threshold temperature may be dependent on the particular
construction (packaging, chemical formulation for example) of the
particular battery used. Techniques such as active cooling of the
battery pack, or heat transfer means such as a heat sink, may often
be insufficient to retain the battery pack within its preferred
safe operating range.
[0057] Following deactivation of the heater plates, the control
system may prevent the hair styling appliance from being used again
until the battery temperature has fallen below either the battery
threshold temperature at which power down was previously initiated,
or below a lower `reactivation` temperature which would be set to a
temperature below the battery threshold temperature.
[0058] Another technique that may be used to prevent heat build-up
in the battery power source is to slow the rate of heating by
throttling the maximum current delivered or using higher resistance
heating elements. However, adopting such a technique may mean that
the temperature of a heater plate cannot be changed very rapidly,
which may lead to a poor transient response.
[0059] Further, an ambient temperature sensor, such as temperature
sensor 5060 in FIG. 5 may be used to monitor the ambient
temperature (i.e. the temperature surrounding the hair styling
appliance) and prevent power delivery to the heater plates if an
ambient temperature threshold is exceeded. An ambient temperature
sense signal A.sub.Tsense 5061 is then generated and fed into the
microcontroller 5061. In embodiments, this ambient threshold
temperature may be a value in the range of 25-35 degrees C., for
example 25 degrees C. or 33 degrees C. Such ambient temperature
sensing may be used as a further safety mechanism to protect
against overheating of the hair styling appliance.
[0060] This is particularly useful in warmer environments in which
the battery which may heat up too fast (such as outside in hot
climates, or in a hot indoor environment). A user may then be
preventing from turning on the hair styling appliance until the
ambient temperature has reduced. Thus, the microcontroller/control
means may be arranged such that power is only supplied to the
heating elements/plates when the sensed ambient temperature is
below an ambient threshold temperature.
[0061] In one or both instances above, if either the ambient or
battery threshold temperatures are exceeded; visual or audio
feedback may be provided to the user to indicate that the device
has entered a safety mode or indicate the temperature status.
[0062] In a first control mode the microcontroller/control means in
FIG. 5 is configured to lower the maximum current draw by operating
the heaters in anti-phase. This means that in an embodiment having
two heater electrodes (one for each heater), only one heater
element may be powered at a time in the embodiment in FIG. 5.
Operating in anti-phase, there may also be periods where both
heaters electrodes are off, such as when both heater plates are at
a desired operating temperature. Given a current draw of `I` for
one heater arranged to heat an entire heater plate, when two
heaters are powered simultaneously to heat two heater plates, the
current draw may be approximately `2I`. Using this convention, the
maximum current draw is limited to the current draw for driving one
heater (i.e. `I`, the current draw for one heater arranged to heat
an entire heater plate). This means that the controller may be
configured to prevent all (both in the embodiment of FIG. 5) heater
electrodes being powered at the same time.
[0063] FIGS. 6a and 6b show a graph for each heater in an appliance
having two heaters and operating according to the preceding
paragraph. As before, the microcontroller 506 uses pulse width
modulation power control to control power delivery to the two
heaters. It will be observed from FIGS. 6a and 6b that both heater
electrodes are now not powered at the same time within each heating
cycle (here labelled `c`). The dotted lines between the Figures
show instances of one heater starting or stopping--note there is no
overlap. In a heating cycle (`c`), each of the heaters below
temperature are powered in a sequence which may be fixed or
determined by the microcontroller, but only one at a time. As
before, the heating cycle may be between 100 .mu.s and 500 ms and
thus the controller rapidly switches the delivery of the power
between the two heaters such that, as far as the user is concerned,
both heaters appear to be heating up simultaneously.
[0064] As will be apparent to those of ordinary skill in the art
from FIG. 5, the controller 506 controls this delivery of power to
the first and second heaters by generating control signals 708 that
cause the decode/drive enable unit 706 to open and close the
switches 702 and 704. In some cases, the control signals 708 may be
directly used to control the switching of the switches 702 and
704.
[0065] The microcontroller may implement a control algorithm
configured to allocate equal percentages of a heating cycle `c` to
each heater, for example 50% of the time. Typically this may be the
case when a user powers on the appliance to heat both heater plates
to the desired operating temperature evenly and as fast as
possible. However, in the event that one heater plate heats up
slower than the other, a higher portion of time in any given
period/heating cycle `c` may be allocated to the cooler heater
plate. Furthermore, in the event one heater plate cools faster than
the other when placed about a quantity of hair, the
microcontroller, in response to a temperature dependent sense
signal, may act accordingly to allocate a higher portion of heating
time in any one heating cycle to power the heater in the cooler
heating plate.
[0066] In some embodiments of the hair styling appliance, there may
be multiple heating zones on each heater plate, as shown in FIG. 3
for example and also shown in GB2477834, herein incorporated by
reference. Each heating zone may comprise a separate heater
electrode arranged to heat a portion of the heater plate. In such
embodiments, it may then be permissible to simultaneously heat
multiple heating zones in many different configurations. The
controller may therefore be configured to prevent all the heater
electrodes distributed across one or more plates being powered at
the same time (or for only short periods of time).
[0067] As previously discussed, we generally consider a current
draw `I` to correspond to the current draw necessary to power a
heater electrode heating an entire heater plate. Thus, in
embodiments having multiple heating zones on a heater plate, one
electrode in each zone may be considered to draw (for the purposes
of comparison only), a portion of current draw `I`. In an
embodiment having two heating zones on each heater plate, i.e. four
heating zones in total, each zone may be considered to draw a
current of 0.5I (presuming the resistances are generally the same).
A maximum preferred current draw `I` may therefore correspond to
powering two zones simultaneously. Any two zones: both on the same
plate, or one on each plate may be simultaneously powered. This
means that in the event a quantity of hair is placed on only one
section of the heater plates, such that only one zone needs to be
powered to retain the desired operating temperature, then opposing
zones on two heater plates may be simultaneously powered whilst
staying within the preferred current draw limit (`I`) to prevent
the battery source overheating.
[0068] It will be appreciated that the maximum preferred current
draw to prevent the battery source overheating may not be `I`, it
may instead be higher or lower than this, Therefore, in some
embodiments it may then be possible to power different combinations
and numbers of heating zones simultaneously without the battery
source overheating. By way of example, in an embodiment having two
heater zones on each of two heater plates, given a preferred
maximum current draw of `1.5I`, it may then be possible to power
three heater zones simultaneously whilst staying within the
preferred current draw limit.
[0069] Table 1 below shows exemplary combinations of the maximum
zones that may be powered at any one time. The `nominal current
draw` column provides examples of the nominal current draw limit,
defined in multiples of the current draw of one heater arranged to
heat an entire heater plate. Accordingly, for the purposes of this
illustrative example, the current draw of two heater electrodes,
each heating half of a heater plate, is deemed the same as one
heater element powering an entire heater plate. It will however be
appreciated that in practice the current draw may be different.
TABLE-US-00001 Zones per Number of plates Nominal Zones powered at
plate in appliance draw `I` any one time 1 2 1 1 2 2 1 2 3 2 1 3 1
2 1.5 1 2 2 1.5 3 3 2 1.5 3
[0070] Returning now to the embodiments shown in FIG. 5 having one
heater electrode in each of two plates, in a second control mode
the microcontroller may allow periods of overlap in which both
heaters are powered simultaneously to heat up both heater plates at
the same time. Given the nominal preferred current draw of `I`,
limited periods of a higher current draw may be permitted, so long
as these higher current draw periods are interleaved with rest
periods in which the nominal preferred current draw is not
exceeded. So as to prevent overheating, the duration of overlap may
be limited by the microcontroller/control means. The
microcontroller/control means may be configured to limit this
overlap to a predetermined duration within a fixed period of time
based on predetermined characteristics of the battery. The
microcontroller may permit, for example, simultaneous heating to
only take place during the initial heat up from power on, then
revert to the first mode of operation. In other words, the
controller may be configured to limit a duration in which the two
heater electrodes are simultaneously powerable by the power source.
This may also be dependent on the battery temperature or ambient
temperature.
[0071] In an enhancement to the second control mode the overlap
control may be variable, being controlled, for example, in response
to feedback from a battery temperature sense signal 5051 as
depicted in FIG. 5. In this variant, the microcontroller may then
actively monitor the temperature of the battery source, controlling
the permissible overlap in which the nominal preferred current draw
may be exceeded in response to the temperature of the battery
source. This may be useful to allow both heaters (based on an
embodiment have one heater element in each heater plate) to be
driven simultaneously from cold at power on, with the
microcontroller then disabling any overlap in heating once the
heaters are first up to temperature.
[0072] By way of example, FIGS. 6c and 6d show a graph for each
heater in an appliance having two heaters where overlap is
permitted. In the first phase, the battery temperature is within
the preferred operating range and so the microcontroller is
configured to operate in the second control mode with periods in
which both heaters are heated simultaneously. In the second phase,
the battery temperature sensor may sense the temperature
approaching (or exceeding) a threshold temperature which results in
the microcontroller changing to the first control of operation in
which the heaters are powered in anti-phase. The microcontroller
may then optionally return to the second control mode when the
temperature of the battery source drops. The dotted lines between
the Figures show regions of overlap in heaters being powered in the
first phase.
[0073] The second technique may also be implemented for embodiments
having multiple heating zones on one or more of the heater plates.
Incorporating the second technique, the microcontroller may then
permit various combinations of zones to be heated simultaneously as
previously described, with periods in which the nominal preferred
current draw is exceeded by powering further heating zones for a
limited period of time. This means that the controller may be
configured to limit a duration in which at least two or more of the
heater electrodes are simultaneously powerable by the battery power
source.
[0074] FIG. 7 shows a cross-sectional view of an illustrative
embodiment of an arm 700 of a hair styling appliance. The arm 700
comprises an outer casing 712 to which other components of the hair
styling appliance are secured. A heater element 704 is positioned
on heater plate 702 to form a hair styling heater assembly. The
hair styling heater assembly is then retained on the arm by the use
of a thermally insulating support structure 714.
[0075] The heater plate 702 comprises a styling surface 715 on one
side that contacts the hair to be styled during use. On the other
side of the heater plate two L-shaped recesses 709a, 709b provide
sockets for securely fixing the hair styling heater assembly to the
thermally insulating support structure 714.
[0076] The thermally insulating support structure 714 is formed
from insulating material and may, for example, be constructed from
a similar material to the casing. The support structure 714
comprises a pair of L-shaped projections 708a, 708b arranged to fit
into the 709a, 709b recesses in the heater plate 702 and couple the
heater plate and support structure together. To allow the
projections to fit into the recesses, they may have a small degree
of flex such that then can snap-fit into the recesses, thereby
securely fixing the heater plate and support structure together. It
will be appreciated however that other means for coupling the hair
styling heater assembly and the support structure are possible, and
the example shown in FIG. 15 is purely illustrative of one way of
doing so.
[0077] To secure the support structure 714 to the casing, sprinted
members 710a and 710b are used. These are secured at one end to the
casing and at the other end to the support structure. In the
illustrative embodiment shown in FIG. 15, compression springs are
used which bias the heater assembly and support structure away from
the arm. These allow the heater plate to move relative to the
casing during styling, allowing the plates to retain contact with
varying thicknesses and changes in the profile of hair clamped
between opposing pairs of styling surfaces on the heater plates. It
will be appreciated that various other arrangements may be used
that provide allow for movement of the heater plates.
[0078] This heater assembly arrangement provides several
advantages: [0079] 1. Firstly, it reduces the width of the outer
casing needed to retain the hair styling heater assembly as no
retaining lugs or fixings are now needed at the sides of the heater
assembly. [0080] 2. Secondly, with no protrusions extending to one
or more sides of the heater plate 702, the widest part of the
heater plate is the styling surface 715. Such an arrangement is
particularly advantageous during manufacturing as it allows the
heater plates to be closely packed, with no or minimal gap between
them. This allows a large number of styling surfaces to be screen
printed, as if they were one large surface, improving the
efficiency of the printing process.
[0081] The skilled person will appreciate that the techniques we
have described above may be employed for a range of hair styling
appliances including, but not limited to, a hair straightener, a
hair crimping device, and a hair curler. The skilled person would
also appreciate that features from many of the embodiments are
interchangeable and not limited to the specific embodiment they are
described in relation to.
[0082] No doubt many other effective alternatives will occur to the
skilled person. It will be understood that the invention is not
limited to the described embodiments and encompasses modifications
apparent to those skilled in the art lying within the spirit and
scope of the claims appended hereto.
* * * * *