U.S. patent application number 10/861252 was filed with the patent office on 2004-11-04 for hairdryer.
Invention is credited to Collier, Nicholas, Ridley, Mark, Sunderland, Joseph W..
Application Number | 20040216322 10/861252 |
Document ID | / |
Family ID | 33313917 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040216322 |
Kind Code |
A1 |
Collier, Nicholas ; et
al. |
November 4, 2004 |
Hairdryer
Abstract
A hairdryer comprises a housing, a fan mounted in the housing,
driven by a battery powered motor, creating an airflow through the
housing. A burner is in the housing in the airflow passage. The
burner has fuel supply. An aerofoil-sectional sleeve baffle element
surrounds the burner to separate the airflow passage into a first
passage in contact with the burner, whereby the airflow in the
passage is heated, and a second passage separated from the burner.
A coned exit baffle is arranged to mix the airflows exiting
hairdryer. An electronic control means pulses a solenoid valve to
control fuel supply to the burner and thus the heat out-put
therefrom.
Inventors: |
Collier, Nicholas;
(Cambridge, GB) ; Sunderland, Joseph W.;
(Wakefield, GB) ; Ridley, Mark; (Cambridge,
GB) |
Correspondence
Address: |
DARBY & DARBY P.C.
P. O. BOX 5257
NEW YORK
NY
10150-5257
US
|
Family ID: |
33313917 |
Appl. No.: |
10/861252 |
Filed: |
June 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10861252 |
Jun 4, 2004 |
|
|
|
PCT/GB02/05498 |
Dec 6, 2002 |
|
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Current U.S.
Class: |
34/97 |
Current CPC
Class: |
A45D 20/06 20130101;
A45D 2020/065 20130101; A45D 20/10 20130101 |
Class at
Publication: |
034/097 |
International
Class: |
A45D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2001 |
GB |
0129243.2 |
Jul 31, 2002 |
GB |
0217741.8 |
Dec 18, 2003 |
GB |
0329318.0 |
Claims
1. A hairdryer comprising: a housing defining an air passage; a
battery adapted to power a motor and a fan driven by the motor to
drive air down the air passage; a burner in the air passage and in
the form of a sleeve enclosing at its open end a catalyst; a
combustible gas supply flow to the burner; a first baffle, to
deflect combusted gas exiting the burner so as to mix with air
after flowing around the burner; and a second baffle, to shroud the
burner and prevents air that flows in the passage around the baffle
and burner from cooling the burner; wherein the first baffle is
coned in the direction of air flow.
2. A hairdryer as claimed in claim 1, in which the sleeve is finned
behind the burner to shed heat, conducted from the burner, through
radiation and convection to the surrounding airflow.
3. A hairdryer as claimed in claim 2, in which said second baffle
extends from one of said fins.
4. A hairdryer as claimed in claim 3, in which said second baffle
extends from the fin of the sleeve which is closest to the
burner.
5. A hairdryer as claimed in claim 1, in which the burner includes
a catalyst in the form of a coil of platinum coated wire.
6. A hairdryer as claimed in claim 1, in which the first baffle
comprises a ceramic block that leaves an annular space in the air
passage through which the combusted gas and air flow.
7. A hairdryer as claimed in claim 1, in which the first baffle is
truncated at its rear end in the direction of air and combusted gas
flow to create turbulence in the flow to ensure complete mixing of
the air and combusted gas.
8. A hairdryer as claimed in claim 1, in which the first baffle
comprises a ridge facing the burner.
9. A hairdryer as claimed in claim 1, in which a third baffle is
disposed upstream of the burner and creates a tubular flow of the
air driven by the fan.
10. A hairdryer as claimed in claim 9, in which said third baffle
comprises the motor being arranged in the air passage downstream of
the fan.
11. A hairdryer as claimed in claim 9, in which the third baffle
comprises a cupped plate.
12. A hairdryer as claimed in claim 1, in which the burner
comprises a port in the sleeve downstream of said first baffle and
through which air is drawn by, and to mix with, with gas supplied
through the sleeve and so as to create said combustible gas.
13. A hairdryer as claimed in claims 12, in which a third baffle is
disposed upstream of the burner and creates a tubular flow of the
air driven by the fan and said third baffle shrouds the port and
creates a positive pressure at its entrance.
14. A hairdryer as claimed in claim 1, in which the fan is a radial
fan drawing air axially through an end opening of the housing and
expelling the air radially from the fan against shrouding that
deflects the air into a tubular flow.
15. A hairdryer as claimed in claim 14, in which said shrouding
comprises the housing itself.
16. A hairdryer as claimed in claim 1, in which there are a
plurality of said burners in the air passage, arranged with their
longitudinal axes parallel.
17. A hairdryer as claimed in claim 16, in which there are two of
said burners in the air passage, the first baffle comprising a
ridge parallel a line joining said longitudinal axes, and a hip at
each end substantially on the longitudinal axis of the respective
burner.
18. A hairdryer comprising: a burner; a fuel reservoir storing
fuel; an electromechanical, biased closed, solenoid valve for
controlling fuel supply from the reservoir; and an electronic valve
control circuit wherein pulse width modulation of the on/off period
of the valve regulates the heat level of the burner.
19. A hairdryer as claimed in claim 18 in which the control circuit
includes a valve control element that is electrically isolated from
the control circuit.
20. A hairdryer as claimed in claim 19 in which the valve control
element is opto-isolated from the control circuit.
21. A hairdryer as claimed in claim 18 in which the control circuit
includes a condition sensor.
22. A hairdryer as claimed in claim 21 in which the condition
sensor comprises at least one of an under-temperature or
over-temperature sensor.
23. A hairdryer as claimed in claim 18 further comprising a flow
passage and at least one baffle diverting flow in the passage in
which a condition sensor is provided in conjunction with the
baffle.
24. A hairdryer as claimed in claim 23 in which the condition
sensor comprises at least one of an under-temperature or an
over-temperature sensor.
25. A hairdryer as claimed in claim 23 in which the baffle shrouds
the burner.
26. A hairdryer comprising: a) a housing; b) a fan mounted in the
housing, driven by a battery powered motor and creating an airflow
in through an air inlet of the housing, along an airflow passage
through the housing and out through an air outlet of the housing;
c) a burner in the housing in the airflow passage; d) a gaseous
fuel supply for the burner; e) a baffle element adjacent the burner
to separate the airflow passage into a first passage in contact
with the burner, whereby the air flow in said first passage is
heated to a first temperature, and a second passage separated from
the burner; and f) an exit baffle before said air outlet and
arranged to mix the airflows exiting said first and second passages
so that said mixed air has an exit temperature less than said first
temperature.
27. A hairdryer as claimed in claim 26, in which a shroud is behind
the burner with respect to said airflow to protect the burner from
direct impacts from said airflow.
28. A hairdryer as claimed in claim 26, in which said baffle
element is a sleeve surrounding the burner dividing the airflow
passage into said first passage, being annular delimited internally
by the burner and externally by the baffle element, and said second
passage, being annular delimited internally by the baffle element
and externally by the housing.
29. A hairdryer as claimed in claim 26, in which pressure
enhancement means increases the pressure of the airflow in the
first passage, slowing it down.
30. A hairdryer as claimed in claim 29, in which said pressure
enhancement means comprises an aerofoil section of said baffle
element encouraging more airflow into said second passage than said
first passage.
31. A hairdryer as claimed in claim 28, in which said pressure
enhancement means comprises an aerofoil section of said baffle
element encouraging more airflow into said second passage than said
first passage, and in which a longitudinal section of the wall of
the sleeve is said aerofoil.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of International
Application No. PCT/GB2002/005498 filed Dec. 6, 2002. The
International application published in English on Jun. 12, 2003 as
WO 2003/047387.
FIELD OF THE INVENTION
[0002] This invention relates to cordless hairdryers of the type
comprising a rechargeable battery to power a motor that drives a
fan, and a gas canister to supply gas to a catalyst for flameless
combustion and which provides heat to the air driven by the
fan.
BACKGROUND OF INVENTION
[0003] The concept of such a hairdryer is well known, (see for
example, U.S. Pat. No. 5,009,592, U.S. Pat. No. 4,635,382, U.S.
Pat. No. 4,800,654, U.S. Pat. No. 4,903,416 DE-A-3103843) but no
commercial product has yet been launched on the market. The reasons
for this are complex and are connected with, among other things,
the inefficiency of batteries and the inability to convert the
potential energy in the gas to heat in the air in an efficient
way.
[0004] One of the problems addressed by the invention is to ensure
that electronic or electrical failure does not compromise product
safety, especially in view of the proximity of the gas reservoir
and electrical components.
[0005] Burners for such hairdryers are preferably of the flameless
type, employing a catalyst that supports combustion of the fuel at
a lower temperature than would be the case in the absence of the
catalyst.
[0006] Catalytic burners are safer, but sensitive, however, to
changes in airflow and are easily extinguished; Preferably, two
burners are present so that if one goes out the other can relight
the extinguished one, before any safety mechanism cuts-off the fuel
supply and necessitates restarting of the hairdryer.
[0007] However, the very nature of hairdryers means that their
airflow is frequently disturbed, in use, by the manipulations
imposed by the user. Sometimes the outlet of the hairdryer will be
blocked,,temporarily, by being held too close to the head, or even
to thick wedges of hair. At other times, all exit resistance is
suddenly removed, so that gushes of air pass through the hairdryer.
Unfortunately, to get the air hot for hair drying, it needs to come
into contact with the burner. Indeed, the residence time of the air
in the hairdryer is very short, given that the quantity of air
required by a satisfactory hair dryer is in the order of 10 to 20
litres per second.
[0008] One approach is for the burner to heat a good heat conductor
which is shaped into fins so that the air, passing over the fins
becomes heated. However, there are few conductors that can conduct
the heat fast enough for this application. Ideally, the air needs
to come into direct contact with the burners and the hot exhaust
gases to get sufficient heat quickly enough. But that is the nub of
the problem: because instantaneous significant variations in
airflow will over-cool, over-heat, or extinguish the burner, it is
difficult to achieve the desired result without rendering the
hairdryer too sensitive to such fluctuations.
[0009] Another approach is to heat plates disposed in front of the
burners as disclosed in U.S. Pat. No. 5,155,925, but this disturbs
the air flow significantly.
[0010] It is an object of the present invention to provide a
hairdryer that overcomes the difficulties experienced, or at least
mitigates their effects.
SUMMARY OF THE INVENTION
[0011] In accordance with the invention there is provided a
hairdryer comprising:
[0012] a housing, defining an air passage;
[0013] a battery, adapted to power a motor and a fan driven by the
motor to drive air down the air passage;
[0014] a burner, in the air passage and in the form of a sleeve
enclosing at its open end a catalyst; and
[0015] a combustible gas supply flow to the burner;
[0016] wherein a first, coned baffle is provided to deflect
combusted gas exiting the burner so as to mix with air after
flowing around the burner; and
[0017] a second baffle is provided to shroud the burner and prevent
air that flows in the passage around the second baffle and burner
from cooling the burner.
[0018] With this arrangement of heating the air by mixing the
airflow with combusted gas after its exit from the burner, and by
shrouding the burner so that there is no danger of the burner being
cooled by the airflow, the risk that flameless combustion might be
terminated is eliminated.
[0019] Preferably, the sleeve is finned behind the burner to shed
heat, conducted from the burner, through radiation and convection
to the surrounding airflow.
[0020] Said second baffle may extend from a fin of the sleeve,
ideally the one closest to the burner.
[0021] The burner may include a catalyst in the form of a coil of
platinum coated wire.
[0022] The first baffle preferably comprises a ceramic block that
leaves an annular space in the air passage through which the
combusted gas and air flow. Preferably, the first baffle is
truncated at its rear end in the direction of air and combusted gas
flow to create turbulence in the flow to ensure complete mixing of
the air and combusted gas.
[0023] Preferably, a third baffle is disposed upstream of the
burner and creates a tubular flow of the air driven by the fan.
Said third baffle may comprise the motor being arranged in the air
passage downstream of the fan.
[0024] Preferably, the fan is a radial fan drawing air axially
through an end opening of the housing and expelling the air
radially from the fan against shrouds that deflect the air into a
tubular flow. Said shrouding may comprise the housing itself.
[0025] Preferably, there are a plurality of said burners in the air
passage, arranged with their longitudinal axes parallel. In this
event, when there are two burners, the first baffle comprises a
ridge parallel a line joining said longitudinal axes, and a hip at
each end substantially on the longitudinal axis of the respective
burner.
[0026] In accordance with another aspect of the present invention
there is provided a hairdryer comprising:
[0027] a) a housing;
[0028] b) a fan mounted in the housing, driven by a battery powered
motor and creating an airflow in through an air inlet of the
housing, along an airflow passage through the housing and out
through an air outlet of the housing;
[0029] c) a burner in the housing in the airflow passage;
[0030] d) a gaseous fuel supply for the burner;
[0031] e) a baffle element adjacent the burner to separate the
airflow passage into a first passage in contact with the burner,
whereby the air flow in said first passage is heated to a first
temperature, and a second passage separated from the burner;
and
[0032] f) an exit baffle before said air outlet and arranged to mix
the airflows exiting said first and second passages so that said
mixed air has an exit temperature less than said first
temperature.
[0033] Preferably, a shroud is behind the burner with respect to
said airflow to protect the burner from direct impacts from said
airflow.
[0034] Accordingly, this aspect of the present invention is
characterised by the airflow being divided, so that only a
proportion of the total airflow passes the burner and, as a result,
that air gets much hotter than suitable for drying hair. However,
since there is a much smaller flow over the burner, changes in
total airflow have much less impact on the airflow over the burner.
Moreover, beyond the burner, the hot air mixes with the remaining
air and is cooled in the process, while at the same time warming
the air that flows down the second passage separated from the
burner, so that mixed air at a suitable hair-drying temperature
exits the housing.
[0035] Preferably, said baffle element is a baffle sleeve
surrounding the burner dividing the airflow passage into said first
passage, being annular and delimited internally by the burner and
externally by the baffle element, and said second passage, being
annular and delimited internally by the baffle element and
externally by the housing.
[0036] Preferably, pressure enhancement means increases the
pressure of the airflow in the first passage, slowing it down. Said
pressure enhancement means may comprise an aerofoil section of said
baffle element encouraging more airflow into said second passage
than said first passage. When said baffle element is a sleeve, a
longitudinal section of the wall of the sleeve is said
aerofoil.
[0037] According to another aspect of the invention, there is
further provided a hairdryer comprising a burner, a fuel reservoir
storing fuel, an electromechanical, biased closed, solenoid valve
for controlling fuel supply from the reservoir, and an electronic
valve control circuit, wherein pulse width modulation of the on/off
period of the valve regulates the heat level of the burner.
Preferably the control circuit includes a valve control element
that is electrically isolated from the control circuit; for example
it can be opto-isolated. The control circuit may include one or
more condition sensors, for example an under-temperature or
over-temperature sensor.
[0038] According to another aspect of the invention there is
provided a hairdryer, preferably a cordless hairdryer, comprising a
burner, a flow passage, and at least one baffle diverting flow in
the passage, in which a condition sensor is provided in conjunction
with the baffle. Preferably the condition sensor is an
under-temperature or over-temperature sensor. Preferably the baffle
shrouds the burner, preventing airflow from cooling the burner
and/or deflects combusted gas exiting the burner so that it mixes
with air flowing around the burner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Embodiments of the invention are further described
hereinafter, by way of example, with reference to the accompanying
drawings, in which:
[0040] FIG. 1 is an exploded perspective view of the main
components of a hairdryer according to the present invention;
[0041] FIG. 2 is a section through the hairdryer;
[0042] FIG. 3 shows a control and safety circuit diagram for the
hairdryer;
[0043] FIG. 4 shows user controls and indicators for the
hairdyer;
[0044] FIG. 5 shows one possible component format for the
hairdryer;
[0045] FIG. 6 shows an alternative possible format for the
components of the hairdryer;
[0046] FIG. 7a is an exploded diagram showing an alternative format
for the hairdryer;
[0047] FIG. 7b is a schematic side sectional view showing the
format of FIG. 7a;
[0048] FIG. 8a is an exploded diagram showing a further alternative
format for the hairdryer;
[0049] FIG. 8b is a schematic side sectional view showing the
format of FIG. 8a;
[0050] FIG. 9a is an exploded diagram showing a further alternative
format for the hairdryer;
[0051] FIG. 9b is a schematic side sectional view showing the
format of FIG. 9a;
[0052] FIG. 10a is an exploded diagram showing a further
alternative format for the hairdryer;
[0053] FIG. 10b is a schematic side sectional view showing the
format of FIG. 10a
[0054] FIG. 11a is an exploded diagram showing a further
alternative format for the hairdryer;
[0055] FIG. 11b is a schematic side sectional view showing the
format of FIG. 11a;
[0056] FIG. 12a is an exploded diagram showing a further
alternative format for the hairdryer;
[0057] FIG. 12b is a schematic side sectional view showing the
format of FIG. 12b; and
[0058] FIG. 13 is a schematic illustration of another hairdryer in
accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0059] Referring to FIGS. 1 and 2, a hairdryer 10 comprises a
housing 12 which at one end consists of two clamshell halves 14a,b,
a middle, tubular section 16, and an end nozzle 18. In the
clamshell end 14 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 clamshells 14a,b are shaped so
that air exiting the fan 22 is deflected longitudinally into the
tubular portion 16 of the housing 12. The arrangement therefore
provides a tubular-like flow of air through the air passage 26
defined by the housing 12. Indeed, the motor 20 defines an annular
start 26a of the air passage 26.
[0060] A cross element 30 is mounted at the entrance to the tubular
part 16 of the housing 12. Screws 33 secure the cross in place. Two
threaded bores 32 are provided in the cross 30, one above the
other, and into each of these is screwed a burner 34.
[0061] Each burner 34 comprises a brass collar 36 screwed into the
bore 32 and provided with a gas terminal 38. A gas pipe (not shown)
from a gas supply (not shown) via a trigger or other supply control
mechanism (not shown) is connectable to the terminal 38. The
terminal 38 is provided with a narrow bore that opens into the
interior of the collar 36, jetting gas therein. A neck 40 of
pressed/sintered metal is screwed into the collar 36. Inside the
neck 40 is disposed a plug 42 of porous metal that serves to
regulate gas flow through the burner 34. On exit from the plug 42
gas flows along a bore 44 of the neck 40 where it mixes with air
drawn in through a cross bore/port 46.
[0062] Air is drawn into the port 46 by virtue of the low pressure
in the bore 44 caused by the high velocity gas flow therein and
controlled by the plug 42. A stoichiometric volume of gas and air
therefore flows along the neck 40 and enters sleeve 50. Finally, in
a broad section 52 of the sleeve 50 is disposed a coiled catalytic
wire, coated with platinum (not shown), where the combustible gas
mix combusts in the absence of a flame.
[0063] Finally, the combusted gases exit the burners 34 and impinge
on a ceramic block baffle 54 to be deflected radially outwardly so
as to mix with the tubular air flow caused by the fan 22.
[0064] A second baffle 56 is provided around the sleeves 50 to
further define the tubular flow by defining annular space 26c of
the air passage 26. The second baffle 56 prevents the air flow from
directly contacting the burners 34 in the region of the cups 52
where the catalyst is disposed. This ensures that the catalyst
remains at the requisite temperature to guarantee complete
combustion of the combustible gas. As shown, the baffle 56 is
mounted on one of several fins 58 of each burner 34, especially
that one closest to the cup 52. However, it could equally well be
mounted on its own spider from the internal surface of housing part
16.
[0065] The fins 58, which also extend to the neck 40, serve to shed
heat developed in the burner cup 52 and conducted along the
material of the burner 34. This heat is shed by both convection
with the surrounding air flow, as well as by radiation. Indeed, the
latter is more significant given a third baffle 60 which is, like
the baffle 56, a disc having a cupped edge. This also defines the
tubular air passage by annular space 26b. The baffle 60 is held
against the cross 50 by the burners 34 passing through apertures
(not shown) in the baffle 60. The baffle 60 guards the ports 46,
and prevents air flow, driven by the fan 22, from drawing gas out
of the ports 46. Instead, stagnant air behind the baffle 60 is at a
relatively high pressure compared with the gas flowing through the
bore 44 of the neck 40 of the burners 34.
[0066] Returning to the second baffle 54, it is mounted on a rod 62
and a further cross 64 inside the tubular housing part 16. On the
end of the housing part 16, a nozzle 18 is disposed, which maybe
shaped to further enhance mixing.
[0067] As noted already, there are two burners 34, each expelling
hot exhaust gases against the baffle 54. The baffle 54 has a ridge
66 aligned with the line joining the longitudinal axes of each
burner. Most of the outflow from each burner is shed to one side or
the other of the ridge 66. However, a hip 68 is formed on the
baffle 54 at either end of the ridge. Gases exiting a sector of
each burner remote from the other burner are thus deflected at
right angles to the ridge-deflected gases. This spreads the
infiltration of the hot gasses into the air flow, so that more
effective mixing occurs with less likelihood of hot spots
occurring. In FIG. 5, however, the arrangement is rotated through
90.degree. so that each burner sheds its output to either side of
the ridge 66.
[0068] The baffle 54 is terminated by a blunt end 70, so that
airflow around it is turbulent, further enhancing gas mixing and
temperature stabilisation.
[0069] As discussed above, in overview the hairdryer includes a gas
burner and gas reservoir and a fan. In addition, as discussed in
more detail below, a control circuit and a battery for powering the
fan are provided. A first baffle deflects combusted gas exiting the
burner so that it mixes with air flowing around the burner. A
second baffle shrouds the burner, preventing airflow from cooling
the burner.
[0070] FIGS. 5 to 12 show various product configurations in
schematic form for a hairdryer according to the invention, with the
housing and control components not shown, for clarity. Each figure
shows a cordless drier designated generally 300 including a fan
302, a burner 304, end nozzle 306, battery pack 308 and gas
canister 310. The fan 302, burner 304 and nozzle 306 define a
generally linear axis 312 with the burner 304 intermediate the fan
302 and nozzle 306, but various configurations of the remaining
components are contemplated. In each case the design avoids
obstruction of the airflow through the fan, to keep the power
required to drive the fan to a minimum.
[0071] Referring to FIG. 5 the battery pack with larger capacity
cells is slung below and parallel with the axis 312, in a 2.times.2
configuration forwardly of the fan 302. The gas canister 310
projects perpendicularly below the axis 312, between the fan 302
and battery pack 308, and can be received in a handle significantly
spaced from the burners, enhancing safety. In FIG. 6 the positions
of the battery pack 308 with larger capacity cells and gas canister
310 are reversed away from the burners, increasing their capacity.
In FIGS. 7a and 7b the arrangement is shown with the gas canister
310 positioned along the axis 312 but rearwardly of the fan 302,
and having a more squat configuration.
[0072] Referring to FIGS. 8a and 8b the arrangement is similar to
that shown in FIG. 6 but with the gas canister 310 placed above
rather than below the axis 312.
[0073] The arrangement of FIGS. 9a and 9b is similar to that of
FIG. 6 but with the profile of the gas canister 310 varied slightly
so as to taper from the base up.
[0074] Referring to FIGS. 10a and 10b the configuration is similar
to that of FIG. 7 except that the orientation of the fan is
changed. In particular is lies below and perpendicular to the axis
312, impelling air towards the axis. As a result a suitable
deflector would be required to divert the air towards the
burner.
[0075] FIGS. 11a and 11b is also similar to FIG. 7 except that the
gas canister 310 is more elongate, as is the fan 302 housing. Also
the battery pack 308 is provided in a 4.times.1 configuration.
[0076] Referring lastly to FIGS. 12a and 12b all of the components
are aligned with the axis 312. The gas canister extends along the
axis rearwardly of the fan 302 and the batteries are distributed
around its circumference. In the embodiment shown the batteries are
provided at 90.degree. intervals in grooves provided in the outer
wall of the canister.
[0077] Turning in more detail to other aspects of the invention,
control and safety circuits 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.
[0078] Referring to the control and safety circuit block diagram
shown as 399 in FIG. 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.
[0079] When the switch 402 is in the on position 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.
[0080] 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 solenoid 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 reopened as the unit cools down.
[0081] 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.
[0082] Both the over-temperature and under-temperature switches
comprise condition sensors which are provided on the baffle 56
shown in FIG. 1.
[0083] 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 be hardwired through the
safety circuit, it is not possible for the igniter circuit to
operate unless the switch 418 is in the ignite position.
[0084] 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-isolatec 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.
[0085] 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.
[0086] In the case where gas regulation is accomplished using a
manual regulator valve 428, the opto isolated control circuit is
omitted and the gas solenoid valve 404 is connected directly to the
terminals of the under-temperature and override switches 416,
418.
[0087] 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.
[0088] 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.
[0089] 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.
[0090] 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.
[0091] 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.
[0092] 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 430 if desired (see section 3.11), 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.
[0093] A possible arrangement 499 of the control switches and
indicators for a hairdryer according to the invention is shown in
FIG. 4.
[0094] A single on/off slide switch 500 controls all power from the
battery pack to the hairdryer. When this switch is in the "off"
position 502, all power is removed from the electronics, fan motor
and solenoid gas shut-off valve ensuring that the gas source is
closed. The on/off slide switch 500 is recessed and must be
depressed before it is possible to move it from the off position.
This is to minimise the possibility of accidental operation.
[0095] Moving the switch to the "on" position 504 provides power to
the electronics and motor control circuits. The fan will run at the
speed selected by the "fan speed"control switch 512. This can be a
2 position switch giving two fan speeds, or a number of speed
settings. The gas is still turned off at this point.
[0096] The on/off slide switch 500 has a third momentary spring
loaded position 506. 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 430
(FIG. 3). Once the burner has lit, a temperature sensor detects
this, an LED lamp 508 lights to indicate gas lit, and the user may
release the switch 500 back to the "on" position 504. If the user
releases the switch before the gas lights, the gas supply will be
switched off, and hairdryer will continue to blow out cold air. The
switch must again be moved to the "ignite" position 506 to switch
on the gas supply and enable the ignition circuit.
[0097] The heat level is controlled by a switch (or manual
regulator) 510 giving two heat levels or a number of heat
settings.
[0098] After use the user moves the slide switch to the "off"
position 502. This stops the fan and closes the gas supply valve.
To re-ignite gas supply the user must repeat the ignition
sequence.
[0099] A "cool shot" options 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.
[0100] As regards ignition of the burner, a preferred
implementation is the electronic spark ignition system 430
discussed above that repeatedly produces a spark until the gas has
been lit or the user releases the ignition button. Such an
electronic system can be used in a similar fashion to a
conventional mains powered dryer.
[0101] The cheaper alternative is a simple mechanical
piezo-ignition system of any appropriate type. The piezo would be
triggered once when the user moves the on/off/ignite switch 500
into the ignition position. The disadvantage is that the user will
need to repeat the process if the burners fail to light, and this
might not be apparent for several tens of seconds if the burners
are not visible.
[0102] Further safety and related aspects include the placement of
the spark electrodes, chosen to further minimise the risk of
ignition of gas products due to the build up of silicone on the
spark electrodes.
[0103] Also, to prevent hair ingress into the product a filter or
grill is placed at the air inlet. This prevents hair being drawn in
and becoming entangled with the fan and keeps other debris out.
[0104] Furthermore, to prevent debris drawn into the hairdryer (eg.
fluff, hair, etc.) from being ignited by the gas burners and
ejected as burning or very hot particles, firstly the air inlet
filter will prevent most particles from being drawn into the
hairdryer, and secondly, the risk of any particles that are drawn
in, coming into contact with a flame or a very hot surface is
minimised by the product design. In particular, the gas burners are
catalytic and therefore burn without a substantial flame at
temperatures of approximately 500-800 C. (rather than 1300 C.).
Furthermore, these hot catalytic surfaces are protected from the
intake air to maintain combustion. Thus particles drawn through the
product are not exposed to high temperatures capable of posing a
hazard.
[0105] Yet further, products that might reasonably be used with the
hair dryer such as gels and hairsprays do not present a safety risk
as a result of various features.
[0106] For example, airflow is controlled through the product so
that aerosols etc are less likely to come into contact with
surfaces that are sufficiently hot to ignite thenm, the spark
ignition source is appropriately placed, the operating temperature
of the catalytic burners is reduced, and combustion occurs in a
safe fashion with the hairdryer.
[0107] The invention as described herein is hence simple to use and
similar in use to existing corded dryers. It provides gas shutdown
in the case of failure of the burners to ignite, or extinguishing
for any reason, two (or more) levels of heat output and fan speeds,
gas ignition, reduced airflow detection and gas shutdown,
over-temperature detection and gas shutdown, under-temperature
detection and gas shutdown (which may be used to detect ignition
failure), battery low indicator and burner on indicator.
[0108] In FIG. 13, a hairdryer 10' comprises a housing 112, which
may be in the form of a clamshell housing commonly used in
implements of this type. A motor 114 is mounted in the housing and
drives an impeller 116. The impeller 116 draws air through an inlet
118 at the rear of the housing 112, which inlet is guarded by a
grill 120 to prevent the ingress of particles or, indeed, hair. The
motor 114 is powered by a rechargeable battery 122 disposed at the
base of a handle 124 of the hairdryer 10'. Also in the handle 124
is a butane gas supply or canister 126. A gas conduit 128 leads to
a catalytic burner 130.
[0109] A baffle element 132 surrounds the burner 130 and divides
the airflow from the fan 116, which exits an outlet 34 at the front
of the housing 112. The airflow is divided into first and second
passages 136,138. Both passages are annular, the first passage 136
being defined by the burner 130 and baffle element 132, whereas the
second passage 138 is defined by the baffle element 132 and the
housing 112.
[0110] Behind the burner 130 is a shroud 140, which shroud serves
to prevent airflow from the fan 116 from directly impinging the
burner 130. Instead, an opening 142 is provided between the sleeve
baffle 132 and the shroud 140.
[0111] Longitudinally, the sleeve baffle 132 has an aerofoil
section, so that most of the airflow is directed through the second
passage 138. This has the effect of slowing the flow through the
first passage 136 and increasing its relative pressure.
[0112] The burner 130 is a catalytic burner and heat both radiates
from the burner, as well as entering the airflow in the first
passage 136 through the exhaust gas products of the combustion. In
either event, the air in the first passage 136 is heated to a
temperature substantially greater than the desired temperature of
the output from the hairdryer 10'. However, the air passing around
the sleeve 132 in the second passage 138 is not heated at all (at
least, not to a significant extent). Air exiting the sleeve 132 at
its outlet 144 mixes with the air from passage 138. An exit baffle
146 is provided in front of the opening 144 to deflect the air from
the first passage to ensure mixing with the air around the baffle
132. Indeed, although shown diamond-shaped, with a tail 148, it may
be preferred that the tail 148 is omitted, so that a blunt end is
provided on the baffle 146. This ensures turbulent mixing of the
two airflows behind the baffle 146.
[0113] In any event, the air exiting the hairdryer 10'through the
outlet 134 has a mean temperature much lower than the temperature
of the air around the burner 130. It is at a temperature suitable
for drying hair, somewhere between 40 and 80.degree. C., depending
on heat settings and fan speeds which are user selectable
items.
[0114] 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.
* * * * *