Note: Descriptions are shown in the official language in which they were submitted.
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- 1
Burner -controlinstrument and method
' The invention relates to a burner control instrument
including a display apparatus. The invention also
relates to a method of controlling a burner.
GB 2,138,610 describes a burner control system in
which the settings of fuel and air valves, which control
the amounts of fuel and air supplied to a burner head,
are controlled by the burner control system. When the
control system is first installed it is commissioned by a
skilled engineer who is able to select appropriate pairs
of fuel valve and air valve settings to achieve optimum
combustion at a variety of levels of output of the
burner. Both during commissioning and during running it
is desirable for the control system to be able to display
certain information to an operator. In the system
described in GB 2,138,610 a basic form of display is
provided which relies on light emitting diodes. Such a
display has a long life but the amount of information
that can be conveyed in such a display is limited.
Liquid crystal displays are very commonly employed
in a wide variety of technologies. For a small liquid
crystal display, backlighting for the display may be
provided by a light emitting diode but for larger
displays the backlighting would typically be provided by
cold cathode fluorescent tubes or electro-illuminescent
devices; such displays may be of almost any selected size
enabling large amounts of information to be displayed, if
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desired. However, the devices employed to provide the
backlighting have a limited lifetime: many such displays
are commercially available at present but they have a
limited lifetime which typically might be 8,000 hours.
A continuous period of 8,000 hours is rather less
than a year, which is an unacceptably short lifetime for
burner control instruments. One known way of extending
the lifetime of the display is to arrange for it to turn
itself off after a predetermined period of inactivity.
The technique is not, however, ideal for a display of a
burner control instrument. One role of such a display is
to show current values of variables relating to the
operation of the burner so that a person can see at a
glance the current situation. In such a case it is
unsatisfactory for the person to have to switch on the
display to activate it but it is also unsatisfactory for
the display to be switched on permanently, because it is
then likely to need replacing within about a year.
It is an object of the invention to provide a burner
control instrument including a display apparatus, which
is convenient to use but which is able to be switched off
during periods of non-use.
According to the invention there is provided a
burner control instrument for controlling at least some
functions of a burner, the instrument including:
a display,
switch means for switching the display on and off,
and
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a sensor for detecting proximity of a person to the
display, the sensor being arranged to cause the switch
means to switch the display on in response to detecting
the proximity of a person.
' S When a burner control system is running, there is
generally no need for an operator to intervene, but there
may well be data that he wishes to see on a display. By
using a proximity detector to detect that a person is
approaching the display, it becomes a simple matter to
l0 arrange for the display to be switched on immediately
before there is a possibility that a person might wish to
read it. When no person is sufficiently close to the
display to read it, the proximity detector remains
inactivated and the display remains switched off,
15 thereby extending the life of the display.
Preferably, timing means are provided, the timing
means being arranged to cause the switch means to switch
the display off after a period of time. Preferably the
display is switched off after a predetermined period of
20 time has elapsed since any detection of a person by the
proximity sensor. With such an arrangement the display
should remain switched on throughout any time period when
a person might wish to see it.
The invention may be applied to any display
25 apparatus where there is a benefit in switching off the
display when it is not being used, but the invention is
especially applicable to liquid crystal displays which
have a limited life, typically because they are backlit
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by light sources of a limited life. The backlighting may
comprise one or more cold cathode fluorescent tubes or
one or more electro-illuminescent devices. Such displays
generally have a lifetime in continuous use of less than
15,000 hours and a period of 8,000 hours without
noticeable degradation of quality is a typical current
industry standard. If by applying the present invention
to a display apparatus it is possible to reduce the
period per day for which the display is switched on to,
say, 2 hours, then a display that would have a life of
8,000 hours continuous use may have its life extended
from less than one year to more than eight years.
The sensor for detecting proximity of a person to
the display may be one whose output is affected simply by
the distance of an object from it or it may be one that
detects movement of an object. Any sensor that is able
to fulfil the function of detecting a person's arrival is
to be regarded as a proximity sensor. Infra red sensors
are currently made in very large volumes for security
applications and are therefore available at low cost,
which makes them especially suitable. Other possible
sensors include those relying on ultrasonics, the Doppler
effect or changes of capacitance.
The present invention still further provides a
method of controlling a burner comprising the following
steps:
controlling the flow of fuel and air to the boiler,
monitoring certain variables relating to the
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combustion process in the burner,
providing a display for displaying information
relating to the combustion process, and
switching the display on in response to detecting
' S proximity of a person to the display.
The method of the invention may be carried out
employing any of the forms of display apparatus described
above. Thus the method may for example further include
the step of switching the display off in response to a
predetermined period of time passing without detection
of proximity of a person .
By way of example, an embodiment of the invention
will now be described with reference to the accompanying
drawings, of which:
Fig. 1 is a perspective view of a burner
control unit,
Fig. 2A is a sectional side view of the control
unit
Fig. 2B is an enlarged sectional side view of part
of the control unit shown in Fig. 2A,
Fig. 3 is a diagram showing the detection range
of a sensor in the control unit,
Fig. 4 is a block diagram showing the operational
relationship of certain components of the
control unit, and
Fig. 5 is a block diagram of a boiler
installation including the burner control
unit of Fig. 1.
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Fig. 1 shows a burner control unit 1 for a fuel
burner of a boiler. Control units of this general kind
are well known and are commercially available; for
example there are the Micro Modulation Control Systems of
Autoflame Engineering Limited. GB 2,138,610 B and GB
2,169,726 B are concerned with inventions relating to
such control units and the disclosures of both those
patent specifications are incorporated herein by
reference.
The burner control unit 1 provides output control
signals to a motor for operating a fuel valve and a motor
for operating an air valve to control the amounts of fuel
and air flowing to the burner. The control unit 1 also
receives input signals comprising for example signals
from sensors which detect the positions of valve members
of the air and fuel valves, one or more signals from
sensors detecting variables relating to the products of
combustion and a signal indicating the temperature of
water in the boiler. In operation the control unit
receives the temperature input signal, compares it with a
desired value and according to the difference in the two
values adjusts the air and fuel valves to alter the rate
of combustion in the boiler. signals relating to the
products of combustion are also received by the control
unit and may be used to make adjustments to the ratio of
air and fuel supplied to the burner, as more fully
described in GB 2,169,726 B.
In order for the burner control unit 1 to operate
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effectively in use with a particular burner installation
it must be commissioned. In the case of the burner
control unit 1 of GB 2,138,610 B such commissioning
includes, amongst other steps, selecting and storing
' S pairs of output control signals for the air and fuel
valves at different levels of output of the burner so as
to optimize the combustion process throughout the whole
operational range of the burner. When the control unit 1
is subsequently operating it compares an input signal
indicating the temperature of water in the boiler with
stored data indicating a desired temperature and,
according to the difference, selects a level of output
for the burner. The control unit is then able to
determine appropriate positions for the air and fuel
valve members and to adjust the members as necessary,
taking account also of input signals relating to the
products of combustion and any other inputs that the
control unit may receive.
During both the commissioning operation and during
subsequent running of the boiler, it is desirable for an
operator to be able to read data from the control unit 1
and for this purpose the control unit 1 is provided with
a display 2 on its front f ace 3. The particular
information presented on the display is not a part of the
present invention and will not be described in detail
here. Examples of information that may be displayed are:
the actual and desired temperature in the boiler: the
current level of operation of the burner; currently
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desired and actual settings of the fuel and air valves;
the amount of oxygen (or other gases) in the combustion
products. It will be appreciated that various other
information can also be displayed as well as or instead
of that just referred to.
The display 2 is a liquid crystal display which in
this particular example is lOcm high and 7.5cm wide.
The display is backlit by cold cathode fluorescent tubes
which are liable to begin to degrade after about 8,000
hours of use. In the particular example described, the
display is an LM 32010P liquid crystal display
manufactured by Sharp Corporation of Osaka, Japan.
In order to extend the life of the display 2 an
arrangement is provided for automatically switching the
display on and off as will now be described further.
The control unit 1 is mounted with its front face 3
approximately vertical and, as shown in Figs. 1, 2A and
2B, has a window 4 in its front face behind which an
infra red sensing arrangement is provided mounted on a
printed circuit board 5. The control unit 1 has a front
face plate 6 which is provided with an opening defining
the window 4. The window 4 is covered by a piece of
polyethylene sheet material 7 that is substantially
transparent to infra red radiation. Mounted on the
printed circuit board 5 is a pyroelectric infra red
sensor 8 and interposed between the sensor 8 and the
sheet material 7 is a fresnel lens 9. As shown in Fig. 3
the arrangement of the sensor 8 and the fresnel lens 9 is
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such that the sensor 8 is sensitive to infra red
radiation arriving at the window 4 in any direction
inclined at an angle of more that about 45° to the plate
6. The sensitivity of the sensor 8 is such that it will
detect a person moving anywhere within this field at a
range of up to about 3 metres. Of course that range can
readily be selected to a different value of, say, between
0.1 and 12m, by changing the lens 9.
Referring now also to Fig. 4 of the accompanying
to drawings, the backlighting of the display 2 is powered
from a power supply lo, with an electronic switch 11
controlling the connection of the power to the display.
operation of the switch is controlled by a switch control
circuit 12 including a microprocessor 12A and software
timer logic 12B. The circuit 12 receives inputs from the
infra red sensor 8 via an amplifier 13 and an analogue to
digital converter 14.
In use, the display 2 is normally disconnected from
the power supply 10. If, however, the sensor 8 detects a
2o person approaching the control unit 1, the switch control
circuit 12 receives an input indicative of that from the
sensor 8 and, in response, operates the switch 11 to
connect the power supply 10 to the backlighting of the
display 2. The person is then able to read the display
without having to take any positive action to switch on
the display. Detection of a person also causes
activation of the software timer logic 12B. After a
predetermined time (for example, 15 minutes) the timer
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logic 12B causes the switch control circuit 12 to open
the switch 11, thereby disconnecting the power supply 10
from the backlighting of the display 2. For a final
portion of that period (for example the last two of the
fifteen minutes), the control circuit 12 again looks for
a signal from the sensor 8 and, in the event that the
sensor detects movement of a person within its range it
will supply a signal indicative of that to the control
circuit 12 which, in response, will reset the timer.
Thus the switch 11 will be opened only after a continuous
period, of the length of the predetermined period, has
elapsed if the sensor 8 has not detected any movement
during the final part of that period.
Of course it may be that a person will pass in the
vicinity of the sensor 8 without having any desire to
read the display 2 and in such a case the display 2 will
be activated unnecessarily. Such wasteful powering up of
the display is unlikely, however, to be a very frequent
occurrence and therefore the life of the display 2 will
be extended very significantly. At the same time, from a
user s viewpoint the operation of the display will be the
same as if it were continuously backlit.
The use of an infra red sensor and associated
control circuitry simply to enable the backlighting of
the display to be switched off when not needed might seem
an excessively complicated and expensive enhancement of a
boiler control unit. In fact, however, such sensors are
not unduly expensive, suitable control circuitry can
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easily be designed and the use of such an arrangement
makes it much more practical to incorporate a liquid
crystal display in a burner control unit. Without the
switch-off facility the expected lifetime of the display
would be only about one year which is too short a period
for a burner control unit.
Fig. 5 shows a particular example of how the burner
control unit of Fig. 1 may be employed in a boiler
installation. The boiler installation shown in Fig. 5
comprises a boiler 20 including a burner head 21, a
combustion chamber 22 and a flue 23. Air is fed to the
burner head 21 from an air inlet 24, via an inlet damper
25 through a centrifugal fan 26 and, finally, an outlet
damper 27. The burner head 21 is able to operate with
either gas or oil as the fuel; gas is fed to the burner
head from an inlet 28 via a valve 29 whilst oil is fed to
the burner head from an inlet 30 via a valve 31. The
boiler has a water outlet pipe 32 with a manually-
operated valve 33 and a water return pipe 34 with a
2o conventional manually-operated valve 35 and an additional
valve 36.
The control unit 1 is connected to various sensing
devices as shown in the drawing. More particularly the
unit is connected via an exhaust gas analyser 37 to an
exhaust gas analysis probe 38, to a load sensor
(temperature sensing device) 39 monitoring the water
outlet of the boiler, and to a flame detection unit 40 at
the burner head. The control unit 1 is also connected
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via an inverter interface unit 41 and an inverter 42 to
the motor of the fan 26 (with interface unit 41 receiving
a feed back signal from a tachometer 26A associated with
the fan 26), via a first air servo motor 43 to the air
inlet damper 25, via a second air servo motor 44 to the
air outlet damper 27, to an air pressure sensing device
45 provided in the air supply duct downstream of the
outlet damper 27, via fuel servo motors 46 to the fuel
valves 29, 3i, to a further servo motor 47 for adjusting
the configuration of the burner head 21, and to a control
unit 36A for the valve 36 on the water return pipe 34 to
the boiler. Thus the control unit 1, including a
proximity sensor 8, performs all the control functions
for the burner unit, including the functions that would
conventionally be carried out by a separate control box
(for example the control of the burner during the
ignition phase).
Whilst the invention has been described above with
reference to a particular form of burner control unit, it
should be understood that the invention can be applied to
any of a wide variety of burner control units performing
all or only some of the burner controlling functions.
Also whilst the unit is referred to as a burner control
unit, it should be understood that the unit may have
other functions not related to the burner, for example,
ones related to a boiler, and indeed those functions may
even be the main functions of the control unit.
In the described embodiment of the invention, it is
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only the power to the backlighting of the display that is
switched off: it will be appreciated of course that it is
a simple matter, if desired, to arrange for the infra red
sensor also to switch off any other elements of the
control unit in response to detecting proximity of a
person. Also, whilst the display described above is a
liquid crystal display, the invention may be applied to
other forms of display.
