Patent Description:
This invention further relates to a wood stove and a kit of a wood stove burn controller and a wood stove air regulator.

Wood burning stoves for heating houses and rooms have been know and are widespread. Although they are called wood burning stoves, wood is not the only type of fuel that is used to generate heat. Other fuels such as coal, coke, briquettes, pellets or other burnable materials can be burned in a wood stove or simply a stove.

The fuel is placed in a combustion chamber, ignited and combustion air, i.e. air with some percentage of oxygen, is supplied to the chamber to allow for a burn or glow of the fuel.

A common type of wood burning stoves has a window, a door, or a door with a window on the front of the wood stove. At least there an opening for refuelling the combustion chamber with fuel.

Typically the burn is tried to be controlled by regulating the flow of combustion air to the combustion chamber either by changing the openness of the door. Some wood stoves have preset settings of valves for regulating the access of combustion air to the combustion chamber.

More recent attempts have been made to actively regulate the flow of combustion air to the combustion chamber. One such attempt is disclosed in European Patent Application <CIT>, which discloses a method for controlling a woodburning stove and an electronic control for a woodburning stove of the type including a combustion chamber which is downwards separated from an ash chamber by means of a grate bottom and having a walling at the rear and at both sides, the control including a thermal sensor and a λ-probe provided in the flue gas exhaust, wherein the control is incorporated in a cabinet which is adapted to be disposed below the ash chamber and which includes a common air intake and one or more regulating valves with a damper plate, each drivingly connected with an electric motor arranged in the cabinet, the motor being control connected with the electronic control, the regulating valve or valves interacting with air ducts for supplying primary and secondary combustion air, the air ducts being disposed side by side at a rear side of the woodburning stove.

Patent application <CIT> discloses a furnace having a firebox with a loading door and a flue gas outlet and having several air inlets, each of which has its own shut-off valve. A common control mechanism is provided for actuating the shut-off valves, with which the valves are opened or closed synchronously and according to their purpose. The control of the desired air passage through the individual air supply openings is thus only possible by actuating a control element.

Patent application <CIT>, upon which the preamble of claim <NUM> is based, discloses a device for controlling the air supply to a stove comprising means for varying the flow of air entering the stove comprising at least one air inlet opening and first means shutter mounted rotatably relative to each other; and means for distributing the combustion air between a primary air circuit and a secondary air circuit comprising at least one primary opening connected to the primary air circuit and a secondary opening connected to the circuit of secondary air and second and third shutter means respectively of the primary and secondary openings, the second and third shutter means are configured to be actuated simultaneously and the second and third shutter means and respectively the primary openings and secondary are arranged rotatably with respect to each other so that the sum of the flow rates of the primary opening and of the secondary opening be constant.

An object of embodiments of the present invention is to provide means and methods that allow a wood stove to perform a more optimised burn.

An object of embodiments of the present invention is to minimise the environmental impact from burning a fuel in the wood stove. This includes a reduction in the creation of particulate matter, sod, NOx, and other harmful by products from a non-optimal burn.

An object of embodiments of the present invention is to allow for an optimal burn of different types of fuel and in particular fuel of the same type, but with different conditions such as wet, normal, dry, or more refined classifications of say wood.

An object of embodiments of the present invention is to maximise the conversion of stored energy in the fuel to useful heat over a desired period of time.

An object of embodiments of the present invention is to provide means and methods that allow for an easy usage of the wood stove. Hereby is understood a reduced need to monitor, change, or otherwise charge the combustion or burn process.

An object of embodiments of the present invention is to provide a method and means for enabling an better and more efficient burn during real and varying conditions where the airflow in a chimney varies according to the specific installation, the weather conditions, where the wood changes according to availability, moist, type, where the user involvement, interest, and expertise varies or combinations thereof.

The invention provides a wood stove air regulator according to claim <NUM>.

The invention also provides a kit comprising a wood stove burn controller and air regulator according to claim <NUM>.

The invention also provides a method for producing a wood stove according to claim <NUM>.

The invention also provides a wood stove according to claim <NUM>.

The invention is described with reference to the drawings, wherein.

<FIG> shows a schematic of wood stove <NUM> with a burn controller <NUM> for controlling a burn in the wood stove <NUM>. The wood stove <NUM> has an exhaust <NUM> that is equipped with exhaust measure means <NUM> such as a thermometer <NUM>" and such as a O<NUM> measuring means <NUM>" like a λ-probe. The exhaust <NUM> is located at the upper end of the wood stove <NUM>.

The measuring means <NUM> are connected to the burn controller <NUM>.

The wood stove <NUM> has an intake <NUM> configured to supply air to the wood stove <NUM>. The intake is located at the lower end of the wood stove <NUM>. The intake <NUM> is controlled by an intake control <NUM> from the burn controller <NUM>. The intake control in this embodiment has a primary valve control <NUM>', a secondary valve control <NUM>", and a tertiary valve control <NUM>‴.

The burn controller <NUM> has means for storing and executing a burn control algorithm <NUM> which controls valve controllers <NUM>.

In this embodiment the burn controller <NUM> has a wood stove door status means <NUM> configured to receive input about weather a door <NUM> is open or closed.

The burn controller <NUM> has a thermostatic controller <NUM> configured to receive input from the thermometer <NUM>' and from a user interface <NUM> via some user interface communication means <NUM>.

The burn controller <NUM> and the user interface <NUM> are configured to send and receive signals.

A first signal <NUM>' is a desired temperature or burn level entered via the user interface <NUM>.

A second signal <NUM>" is a start or stop signal entered via the user interface <NUM>.

A third signal <NUM>‴ is a refill signal send from the burn controller <NUM> to the user interface <NUM>, which refill signal informs that more fuel is needed to maintain the desired temperature or burn cleanliness.

The wood stove <NUM> in this embodiment has a door <NUM> which in this case is a window in front of a combustion chamber <NUM>.

<FIG> shows a wood stove <NUM> with a combustion chamber <NUM> with a base <NUM> and whereto combustion air <NUM> is fed from a air regulator <NUM> and wherefrom a flue gas exhaust <NUM> guided away.

The wood stove <NUM> has the air regulator <NUM> positioned at the lower part of the wood stove below the base <NUM> of the combustion chamber <NUM>.

The air regulator <NUM> has a number of valves <NUM> each connected via an air duct <NUM> to conduct combustion air <NUM> from the outside of the combustion chamber <NUM> to inside the combustion chamber <NUM>.

In particular the air regulator <NUM> has a primary valve <NUM>' that controls the flow of combustion air <NUM>' through a primary air duct <NUM>' from the intake <NUM> to the lower part of the combustion chamber <NUM>. In this embodiment the primary air duct <NUM>' is adapted to guide combustion air <NUM>' through the base <NUM>.

In particular the air regulator <NUM> has a secondary valve <NUM>" that controls the flow of combustion air <NUM>" through a secondary air duct <NUM>" from the intake <NUM> to the middle part of the combustion chamber <NUM>.

In this embodiment the secondary air duct <NUM>" is adapted to guide combustion air <NUM>" to the rear side of the combustion chamber <NUM>, which rear sided is opposite the window or door <NUM>.

In particular the air regulator <NUM> has a tertiary valve <NUM>‴ that controls the flow of combustion air <NUM>‴ through a tertiary air duct <NUM>‴ from the intake <NUM> to the upper part of the combustion chamber <NUM>.

In this embodiment the tertiary air duct <NUM>" is adapted to guide combustion air <NUM>‴ to the front side of the combustion chamber <NUM>, which front side is the same side as the door or window <NUM>.

The wood stove <NUM> has connection means for connecting the exhaust <NUM> or connection to a chimney <NUM>. In this embodiment the exhaust measure means <NUM> are positioned inside the chimney <NUM>. The exhaust measure means <NUM> includes a thermometer <NUM>' and a λ-probe as the O<NUM>-measurement means <NUM>".

<FIG> shows an example of a state diagram for controlling the burn in a wood stove <NUM>. The state diagram is embedded in the burn controller <NUM> as a software programme and in particular as burn control algorithm <NUM>.

The state diagram or state controller has a set of start instructions <NUM> followed by five states during operation. The five states include a <NUM>th state <NUM>, <NUM>th state <NUM>, a <NUM>st state <NUM>, a <NUM>nd state <NUM>, and a <NUM>rd state <NUM>.

The <NUM>th state is a cold start state <NUM> where the wood stove <NUM> is cold meaning.

The <NUM>st state is a warm start state <NUM> where the wood stove <NUM> has been operated and is still warm.

The <NUM>nd state is a combustion state <NUM> where the fuel burns in the wood stove <NUM>.

This allows for the burn controller <NUM> to maintain the burn in the wood stove <NUM> as long as there is fuel and settings and measures require combustion.

The <NUM>rd state is a glow state <NUM> where the fuel glows in the wood stove <NUM>.

The <NUM>th state is an off state <NUM> where the wood stove <NUM> is closed down and the fuel burn is terminated.

During each state <NUM>, <NUM>, <NUM>, <NUM>, <NUM> the burn controller <NUM> controls valves <NUM> in the air regulator <NUM>.

The burn controller <NUM> is configured to receive input from exhaust measures <NUM> and in this case from a user interface <NUM> which measures and inputs are used to determine when the state controller shall make a shift or a transition from one state to the same, "a reset", or another state.

In the show embodiment of the state controller there are transitions or shifts from one state to another state as follows.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 4th state <NUM> to the 0th state <NUM> or from the start state to the OFF-state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the <NUM>th state <NUM> to the <NUM>th state <NUM> or from the cold start state to the cold start state. Such shift or transition from and to the same state is performed if the procedure in the state is not finished or need to be restarted.

<NUM>-<NUM> shift <NUM> is a shift or transition from the <NUM>th state <NUM> to the <NUM>st state <NUM> or from the cold start state to the warm state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 1st state <NUM> to the 1st state <NUM> or from the warm state to the warm state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 1st state <NUM> to the 2nd state <NUM> or from the warm state to the combustion state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 1st state <NUM> to the 3rd state <NUM> or from the warm state to the glow state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 2nd state <NUM> to the 1st state <NUM> or from the combustion state to the warm state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 2nd state <NUM> to the 3rd state <NUM> or from the combustion state to the glow state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 3rd state <NUM> to the 1st state <NUM> or from the glow state to the warm state.

<NUM>-<NUM> shift <NUM> is a shift or transition from the 3rd state <NUM> to the 4th state <NUM> or from the glow state to the off state.

As is apparent other possible shifts such as <NUM>-<NUM>, <NUM>-<NUM>,. etc. are not shown in this embodiment, but they are implementable in a similar way.

<FIG> illustrate valve control schemes for each of the states <NUM>th <NUM>, <NUM>st <NUM>, <NUM>nd <NUM>, <NUM>rd <NUM>, and <NUM>th <NUM> states. Each state is controlled at least one valve control scheme depending on the previous state. The control schemes shown in <FIG> relate to an embodiment of the invention, in which the primary, secondary and tertiary air ducts are controllable by means of respective valves <NUM>, <NUM>', <NUM>", <NUM>'", and <FIG> relate to an embodiment of the invention, in which only the primary and secondary air ducts are controlled by means of respective valves, while the tertiary air duct is kept at a constant position.

Each scheme has an initial value, a PD controller input and a set point value for each of the primary, secondary, and, where applicable, tertiary valves.

<FIG> and <FIG> show an example of a cold start phase <NUM>, the <NUM>th state, with a cold start control <NUM> that includes a cold start valve control scheme <NUM>. The cold start valve control scheme <NUM> has initial values <NUM>, PD controller input values <NUM>, and set point values <NUM> for each of the primary, secondary, and tertiary valves.

There is a primary initial value <NUM>' which in this instance is <NUM> % resulting in that the primary valve <NUM>' is <NUM> % opened for a maximum intake of primary combustion air <NUM>' to the combustion chamber <NUM>.

There is a secondary initial value <NUM>" which in this instance is <NUM> % resulting in that the secondary valve <NUM>" is <NUM> % opened, i.e. <NUM> % closed, for a minimum or zero intake of secondary combustion air <NUM>‴ to the combustion chamber <NUM>.

There is a tertiary initial value <NUM>‴ which in the instance of <FIG> is <NUM> % resulting in that the tertiary valve <NUM>‴ is <NUM> % opened for a maximum intake of tertiary combustion air <NUM>" to the combustion chamber <NUM>. In the instance of <FIG>, the tertiary initial value is fixed at <NUM>% opened.

There is a primary controller input <NUM>' that is unregulated or floating. Likewise the secondary controller input <NUM>" and the tertiary controller input <NUM>‴ are unregulated or floating.

There is a primary set point value <NUM>' that is empty or null. Likewise the secondary set point value <NUM>" and the tertiary set point values are empty or null.

<FIG> and <FIG> show an example of a warm start phase <NUM>, the <NUM>st state or phase, with a warm start control <NUM> that includes a cold to warm start valve control scheme <NUM>, a combustion to warm valve control scheme <NUM>, and a glow to warm valve control scheme <NUM>.

Following the numeration from <FIG>, the cold to warm start valve control scheme <NUM> has:
A primary initial value of <NUM> % resulting in that the primary valve <NUM>' is fully opened for delivering a maximum of primary combustion air <NUM>' to the combustion chamber <NUM>.

There is a primary controller input that regulates the temperature. The regulator is based on a primary set point value Tset according to for example a user input via the user interface or a preset standard desirable temperature.

There is a secondary initial value of <NUM> % resulting in that the secondary valve <NUM>" is fully closed for initially delivering no secondary combustion air <NUM>" to the combustion chamber.

There is a secondary controller input that regulates the oxygen, O<NUM>, level in the exhaust <NUM> towards a secondary set point value of <NUM> % O<NUM>.

In <FIG>, a tertiary initial value of <NUM> % results in that the tertiary valve <NUM>‴ is fully opened for delivering a maximum of tertiary combustion air <NUM>‴ to the combustion chamber <NUM>. In <FIG>, the tertiary initial value is fixed at <NUM>% opened.

In the embodiment of <FIG>, there is provided a tertiary controller input that is left unregulated or floating and with a null nor irrelevant set point value.

The combustion to warm start valve control scheme <NUM> has:
A primary initial value of <NUM>% (<FIG>) resulting in that the primary valve <NUM>' is <NUM> % open for delivering some primary combustion air <NUM>' to the combustion chamber <NUM>. In <FIG>, the primary initial value is between <NUM>% (i.e. closed) and <NUM>%.

There is a primary controller input that regulates the temperature in the exhaust <NUM> towards a primary set point value that is determined by Tset.

There is a secondary initial value that is unchanged (<FIG> and <FIG> alike).

There is a secondary controller input that, in the embodiment of <FIG>, regulates the Oxygen level towards a tertiary set point value of <NUM> % O<NUM>. (<NUM>% O<NUM> in <FIG>).

There is a tertiary initial value of <NUM> % resulting in that the tertiary valve <NUM>‴ is fully open for delivering a maximum of secondary combustion air <NUM>‴ to the combustion chamber <NUM>.

There is a tertiary controller input that is left unregulated or floating and with a null nor irrelevant set point value resulting in that the tertiary valve <NUM>‴ is left at the initial value (<FIG>). At <NUM>, the tertiary initial value is fixed at <NUM>% in <FIG>.

The glow to warm start valve control scheme <NUM> has:
A primary initial value of <NUM> % resulting in that the primary valve <NUM>' is <NUM> % open for delivering some primary combustion air <NUM>' to the combustion chamber <NUM>. In <FIG>, the primary initial value is between <NUM> and <NUM>%.

In <FIG>, there is a secondary initial value of <NUM> % resulting in that the secondary valve <NUM>" is half open for delivering half maximum of tertiary combustion air <NUM>" to the combustion chamber. In <FIG>, the secondary initial value is unchanged at <NUM>.

There is a secondary controller input that regulates the Oxygen level towards a secondary set point value of <NUM> % O<NUM>. In <FIG>, the secondary oxygen set point value is <NUM>% O<NUM>.

There is a tertiary initial value of <NUM> % (<FIG>) resulting in that the tertiary valve <NUM>‴ is fully open for delivering a maximum of secondary combustion air <NUM>‴ to the combustion chamber <NUM>. In <FIG>, the tertiary initial value remains fixed at <NUM>%.

In <FIG>, there is a tertiary controller input that is left unregulated or floating and with a null nor irrelevant set point value resulting in that the tertiary valve <NUM>‴ is left at the initial value.

The warm start control <NUM> is further configured for determining the previous state thereby enabling the desired selection of the valve control scheme <NUM>, <NUM>, <NUM>.

<FIG> and <FIG> show examples of a combustion state <NUM>, the <NUM>nd state, and a combustion control <NUM> controlling a first warm to combustion valve control scheme <NUM> and a subsequent warm to combustion valve control scheme <NUM>. The combustion state of <FIG> is a first combustion state, whereas a second combustion state is described below with reference to <FIG>.

The first warm to combustion valve control scheme <NUM> has:
A primary initial value of <NUM> % resulting in that the primary valve <NUM>' is fully closed for delivering zero primary combustion air <NUM>' to the combustion chamber <NUM>.

There is a primary controller is left unregulated and the primary set point value is null.

There is a secondaryinitial value that is left unchanged.

There is a secondary controller input that regulates the oxygen, O<NUM>, level in the exhaust <NUM> towards a tertiary set point value of <NUM> % O<NUM> (<FIG>) and <NUM>% O<NUM> (<FIG>), respectively.

In the embodiment of <FIG>, a tertiary initial value of <NUM> % results in that the tertiary valve <NUM>‴ is fully opened for delivering a maximum of tertiary combustion air <NUM>‴ to the combustion chamber <NUM>. In <FIG>, the tertiary initial value remains fixed at <NUM>%.

In the embodiment of <FIG>, there is provided a tertiary controller input that regulates temperature towards a temperature determined by a tertiary set point value Tset, whereas no controller input is provided in the embodiment of <FIG>.

The subsequent warm to combustion valve control scheme <NUM> has:
A primary initial value of <NUM> % resulting in that the primary valve <NUM>' is fully closed for delivering zero primary combustion air <NUM>' to the combustion chamber <NUM> (<FIG> and <FIG> alike).

There is a secondary initial value that is left unchanged in the embodiment of <FIG>, whereas the secondary initial value at <NUM> is set to <NUM>% open for the secondary valve <NUM>" in the embodiment of <FIG>.

There is a secondary controller input that regulates the oxygen, O<NUM>, level in the exhaust <NUM> towards a secondary set point value of <NUM> % O<NUM> (<FIG>) and <NUM>% O<NUM> (<FIG>), respectively.

In <FIG>, a tertiary initial value of <NUM> % results in that the tertiary valve <NUM>‴ is fully opened for delivering a maximum of secondary combustion air <NUM>‴ to the combustion chamber <NUM>. In <FIG>, the tertiary initial value remains fixed at <NUM>%.

In the embodiment of <FIG>, a tertiary controller input is provided for regulating temperature towards a temperature determined by a tertiary set point value Tset.

<FIG> and <FIG> show examples of a glow state <NUM>, the <NUM>rd state, and a glow state control <NUM> that controls a warm start to glow valve control scheme <NUM> and a combustion to glow valve control scheme <NUM>.

Before describing the glow state <NUM> of <FIG> and <FIG>, reference is initially made to <FIG>, which shows second combustion phase, i.

The warm start to glow valve control scheme <NUM> of <FIG> includes the following:
A primary initial value that is left unchanged and with a maximum of <NUM> % resulting in that the primary valve <NUM>' is at maximum half opened for delivering half primary combustion air <NUM>' to the combustion chamber <NUM> as a maximum.

There is a primary controller regulates temperature towards a primary set point value determined by Tset.

There is a secondary initial value of <NUM>%, i.e. closing the secondary valve <NUM>".

There is a secondary controller input that regulates oxygen level towards an oxygen level at <NUM> % O<NUM>.

The combustion I state to glow valve control scheme <NUM> of <FIG> includes the following:
A primary initial value that is <NUM> % resulting in that the primary valve <NUM>' is closed for delivering no primary combustion air <NUM>' to the combustion chamber <NUM>.

There is a secondary initial value at <NUM>%, i.e. closing the secondary valve <NUM>".

In <FIG> and <FIG>, the warm start to glow valve control scheme <NUM> includes the following:
A primary initial value that is left unchanged and with a maximum of <NUM> % resulting in that the primary valve <NUM>' is at maximum half opened for delivering half primary combustion air <NUM>' to the combustion chamber <NUM> as a maximum.

There is a primary controller regulates temperature towards a primary set point value determined by Tset (<FIG>) and that regulates oxygen towards an O<NUM> level of <NUM>% (<FIG>).

There is a secondary initial value of <NUM>% resulting in that the secondary valve <NUM>''' is closed.

There is a secondary controller input that is left unregulated with no set point value (<FIG>). In <FIG>, the secondary controller input regulates O<NUM> to a maximum level of about <NUM>%.

In <FIG>, there is provided a tertiary initial value of that is left unchanged with a minimum of <NUM> % resulting in that the tertiary valve <NUM>‴ is opened for delivering smal amounts of tertiary combustion air <NUM>‴ to the combustion chamber <NUM>. In <FIG>, the tertiary value remains fixed at <NUM>%.

There is a tertiary controller input that regulates oxygen level towards an oxygen level at <NUM> % O<NUM>.

The combustion state to glow valve control scheme <NUM> (<FIG> embodiment only) includes the following:
A primary initial value that is <NUM> % resulting in that the primary valve <NUM>' is closed for delivering no primary combustion air <NUM>' to the combustion chamber <NUM>.

There is a secondary initial value of <NUM> % resulting in that the secondary valve <NUM>‴ is closed.

There is a secondary controller input that is left unregulated with no set point value.

There is a tertiary initial value of that is left unchanged with a minimum of <NUM> % resulting in that the tertiary valve <NUM>‴ is slightly opened for delivering small amounts of tertiary combustion air <NUM>" to the combustion chamber <NUM>.

<FIG> and <FIG> show examples of an OFF-state <NUM>, the <NUM>th state, and a OFF state control <NUM> that controls a combustion to glow valve control scheme <NUM>.

There is primary initial value of <NUM> % resulting in that the primary valve <NUM>' is closed for zero delivery of primary combustion air <NUM>' to the combustion chamber <NUM>.

There is a primary controller input that is left unregulated with a null set point value.

There is a secondary initial value of <NUM> % resulting in that the secondary valve <NUM>" is closed for zero delivery of tertiary combustion air <NUM>" to the combustion chamber <NUM>. There is a tertiary control input that is left unregulated with a null set point value.

In <FIG>, there is a tertiary initial value of <NUM> % resulting in that the tertiary valve <NUM>‴ is a slightly open for a delivery of small amounts of tertiary combustion air <NUM>‴ to the combustion chamber <NUM>. In the embodiment of <FIG>, the tertiary initial value remains fixed at <NUM>%. However, in order to avoid heat from the surrounding room to dissipate into the cooled-down stove through the tertiary air duct, it may be closed to <NUM>% in the off state.

In the embodiment of <FIG>, there is a tertiary controller input regulating temperature if the temperature is below <NUM> degrees Celsius. Thereby remaining fuel is slowly extinguished. The tertiary set point value is null.

<FIG> shows an embodiment of an air regulator <NUM> with three valves <NUM>: a primary valve <NUM>', a secondary valve <NUM>", and a tertiary valve <NUM>'". The air regulating box <NUM> has a housing <NUM> with a intake connection means <NUM> and is formed to fit into a wood stove <NUM> so that the intake connection means <NUM> gets combustion air <NUM> from the intake <NUM>.

The air regulator <NUM> has air duct connection means <NUM> for each valve <NUM>.

There is a primary air duct connection means <NUM>' for connecting the air box <NUM> to a primary air duct <NUM>' allowing combustion air <NUM> from the intake <NUM> to be fed the combustion chamber <NUM> as primary combustion air <NUM>' controlled by the primary valve <NUM>'.

Likewise for the separate secondary and tertiary channels.

<FIG> shows and embodiment of a valve <NUM> which is a cylinder valve <NUM> with a valve housing <NUM> and a valve piston <NUM>. The valve piston <NUM> is in extended to a position furthest out of the valve housing <NUM>.

<FIG> shows sectional view of an air box <NUM> with and two cylinder valves <NUM>, one of which is seen in a cross sectional view. In both cases the valve pistion <NUM> is withdrawn into the valve housing <NUM>.

The movement of the valve piston <NUM> is done via an actuator connector <NUM> connected to a actuator means <NUM>. In this case the actuator connector <NUM> and actuator means combination is a shredded linear line that is rotated by a motor thereby linearly moving and positioning the valve piston <NUM> within the housing <NUM> to form a valve port <NUM> due to interaction or relative positioning against a valve port frame <NUM>.

<FIG> shows a cross sectional view of a cylinder valve <NUM> with the valve housing <NUM>, the valve piston <NUM> linearly movable in and out of the valve housing <NUM>. The movement of the valve piston <NUM> is done along the actuator connector <NUM>, which in this case is a screw that can be rotated by a motor as the actuator means <NUM>.

The actuator means <NUM> is controlled by the valve control <NUM> and the arrangement with the calibrated, in particular the relative positioning of the valve port frame <NUM>, the valve housing <NUM> and the valve piston <NUM> so that a signal of <NUM> % open to the valve control <NUM> results in a withdrawal of the valve piston <NUM> into the valve housing <NUM> thereby making a maximum valve port <NUM> opening.

Likewise a signal of <NUM> % open (close) to the valve control <NUM> results in a valve piston <NUM> out of the valve housing <NUM> and closing towards the valve port frame <NUM>.

In this embodiment it is seen that the valve port frame <NUM> has a V-shaped opening so that the size of the valve port <NUM> opening can be controlled more precisely allowing for a finer control of smaller vale port <NUM> openings.

<FIG> shows the temperature of exhaust and the CO<NUM> %-level in the exhaust for a wood stove without the burn controller and air regulator, A, and for a wood stove with the burn controller, B.

Each diagram shows the timely development of the temperature of the exhaust Tex-haust on a scale from <NUM>-<NUM> and the percentage CO<NUM> level in the exhaust on a scale from <NUM>-<NUM> %.

The test has carried out as a standard test according to EN13240 to be able to compare the a burn of a fuel in a standard wood stove with an embodiment of wood stove as disclosed in the case where standard wood stove is fitted with a air regulator, a burn controller and exhaust measures (albeit the O2 sensor being replaced with an eqivalent CO2 sensor).

According to the standard test, there are three conditions or test circumstances: The best user is a laborant, best compromise for the chimney and installation, and best possible fuel load (in moist and weight distribution).

Each spike in the figures represents a refuelling of the wood stove. It is clearly observed that the controlled or regulated burn is more constant. Although there are spikes present, these are narrow. The Texhaust is very stable at about <NUM>.

The standard test shows that the controlled wood stove according to an embodiment of the invention results in a reduction in fuel consumption of about <NUM>-<NUM> %.

The controlled wood stove gives an ease of use with a more stable (i.e. less modulation) room temperature with less refills of wood. No or reduced chances of overheating and consequently a reduced risk of damage to the wood stove and therefore a longer life expectancy of the wood stove.

The controlled wood stove furthermore results in less build-up of soot in the wood stove and the chimney.

As for the environmental impact the controlled wood stove from a cold to a cold state showed emission reductions of about <NUM>-<NUM> % again according to the norm EN <NUM>.

Besides the standard test circumstances (Laboratory Conditions) other normal and abnormal tests have been conducted. These other conditions include: "best user", "worst user", "bad chimney", "moist wood", and "wrong amount of wood". These conditions have been tested for different burn scenarios.

For comparison the un-controlled wood stove in the cases of a best user, worst user and bad chimney for nominal burn condition had efficiencies of <NUM> %, <NUM> %, and <NUM> %, respectively.

Claim 1:
Wood stove (<NUM>) air regulator (<NUM>) comprising at least one valve (<NUM>), such as three valves (<NUM>', <NUM>", <NUM>‴) and with a housing (<NUM>) configured for fitting into a wood stove (<NUM>) and configured for receiving control signals (<NUM>) from a burn controller (<NUM>), wherein the valve (<NUM>) is a cylindrical valve (<NUM>) with a valve piston (<NUM>) and actuation means (<NUM>) for linearly positioning the valve piston (<NUM>) relatively to a valve port frame (<NUM>) for controlling the flow of combustion air (<NUM>) through a valve port (<NUM>),
characterised in that
said valve port frame (<NUM>) is formed with a wide opening towards the end where the valve piston (<NUM>) is in the <NUM> % open position and with a narrower opening towards the end where the valve piston (<NUM>) is in the closed position.