NZ529203A - Improvements to solid fuel burners - Google Patents

Abstract

Disclosed is a solid fuel burner comprising (a) a firebox having a door and at least one aperture therein for air flow purposes, (b) an air control valve capable of adjustment with respect to the firebox to regulate the rate of flow of air into the firebox, the adjustment being functionally linked to the opening and closing mechanism of the door, (c) a temperature sensitive mechanism adapted to firstly, automatically adjust its position relative to the air control valve when the firebox falls below a first substantially pre-determined temperature and to secondly, automatically re-adjust its position relative to the air control valve once the firebox has reached a second higher substantially pre-determined temperature, wherein their arrangement is such that once the door is opened thereby causing a drop in the temperature of the burner to the first pre-determined temperature, the air control valve is prevented from readjustment upon door closure by the temperature sensitive mechanism, until the second pre-determined temperature has been reached.

Description

Patents Form # 5 52920 3 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION AFTER PROVISIONAL NO: 529203 DATED: 30 October 2003 TITLE: Improvements to Solid Fuel Burners I, Werner Johannes Janssens Address: 201 Forest Hill Road, Henderson, Auckland, New Zealand Nationality: A New Zealand citizen do hereby declare the invention for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statement: 130793NZ_Cap_20041014_1446_SP.doc FEE CODE 1050 INTELLECTUArPROPlTYOFFjcE of HI o I NOV 2004 FIELD OF THE INVENTION The present invention relates to improvements to solid fuel burners, in particular but not exclusively, to domestic solid fuel burners used in the home.

BACKGROUND ART KNOWN TO THE APPLICANT Controlled combustion solid fuel burners (e.g. coal, peat or wood) for heating homes and dwellings have been used in New Zealand for many years. In fact, solid fuel burners are still the most common form of domestic heating in New Zealand especially in the South Island where the winters tend to be harsher than in the corresponding regions of the North Island.

During the past twenty years the need to improve air quality in New Zealand cities and in Christchurch in particular, has led to a substantial toughening of the allowed emission standards, especially for wood burners.

Similar restrictions apply in Australia and North America also. Over the years better and more efficient wood burners have been developed in order to comply with the ever tighter standards set by air quality laws.

Improvements to the emission levels of these burners has now reached the stage where further improvements to the type of burner known generally per se are becoming difficult if not almost impossible and no longer cost effective.

Test results achieved in laboratories under ideal conditions where fires are operated by skilled technicians, are often not a true reflection of the heater's performance in real life. It is known that the largest proportion of unwanted particle and gas emissions from controlled combustion wood burners occurs during the period where the fuel loses half its weight. This tends to take place during the first half to one hour after refuelling and again depends on the amount of primary air available and the time for the fuel to reach temperatures above 250 degrees Celsius.

This delay will be prolonged by the time taken to evaporate water from the fuel. Therefore the authorities regulating emission levels are now insisting that only fuel with a moisture content of less than 20% is suitable. Although there is now a greater public awareness of the 130793NZ_SP_CAP spec.doc/CA/SP importance of dry fuel, in practice, lack of storage facilities and supply shortages often lead to the use of inferior fuel.

If such fuel is used in an appliance that is wrongly operated so as to cause a lack of primary air supply immediately after refuelling, a condition arises which can dramatically increase 5 emission levels. Should this condition arise, unwanted emissions can exceed the emission standard by 300 to 600%.

Because there is incomplete combustion the high emission period is stretched over a longer period and because combustion takes place at lower temperatures the appliance efficiencies are also reduced dramatically. It is therefore a prerequisite to efficient combustion and low ^ 10 emission levels to supply the maximum amount of primary air during the period immediately after refuelling. By coincidence or design some manufacturers have incorporated an interlock mechanism between the air control valve and the door catch.

This means that the door can only be opened after the air valve is fully opened. The main objective of this is to alleviate smoke spillage problems. Such a system is often promoted 15 under the guise of being childproof. However its real benefit is the minimising of smoke spilling into the room. Another benefit is that whenever fuel is added to the fire the air control is fully opened.

This would be an excellent factor in achieving ideal post-fuelling conditions, however there is a natural human tendency to reverse actions to complete the re-fuelling operation. This 20 leads to a complete closing of the primary air supply with the earlier mentioned consequences.

It is therefore an object of the present invention to produce an improvement to a solid fuel burner that would tend to alleviate the problems as specified above or which will at least provide the public with a useful choice.

STATEMENTS OF THE INVENTION In its broadest aspect, the present invention provides for a solid fuel burner comprising the following components: a firebox having a door and at least one aperture therein for air flow purposes; 130793NZ_SP_CAP spec.doc/CA/SP an air control valve capable of adjustment with respect to the firebox to regulate the rate of flow of air into the firebox, said adjustment being functionally linked to the opening and closing mechanism of the door; a temperature sensitive mechanism adapted to firstly, automatically adjust its position 5 relative to the air control valve when the firebox falls below a first substantially predetermined temperature and to secondly, automatically re-adjust its position relative to the air control valve once the firebox has reached a second higher substantially pre-determined temperature; wherein their arrangement is such that once the door is opened thereby causing a drop in the 10 temperature of the burner to the first pre-determined temperature, the air control valve is prevented from readjustment upon door closure by the temperature sensitive mechanism, until the second pre-determined temperature has been reached.

This arrangement tends to alleviate the problem because it removes the human element from the air control valve adjustment process.

Preferably, the temperature sensitive mechanism is operatively associated with the air control valve at all times.

The air control valve may be directly or indirectly connected to the firebox and of course, movement of the air control valve to regulate the rate of flow of air into the firebox can occur by translational movement of the valve, rotation and/or revolution of the valve about two 20 mutually identical and/or substantially orthogonal planes.

The air control valve may be biased against movement about either or both plane(s). Preferably the bias is provided by a counter weight.

Preferably, movement of the air control valve to regulate the rate of flow of air into the firebox can occur via both translational and rotational movement of the air control valve with 25 respect to the firebox.

The air control valve and its connection to the fire box could be so adapted as to make the movement of the air control valve caused by the temperature sensitive mechanism to be a intellectual property office of n.z.

I 5 AUG 2005 130793NZ SP CAP spec.doc/CA/nk _ _ _ RECEIVED linked combination of, for example, a translational and then rotational (or vice versa) movement.

Preferably, the movement of the air control valve caused by the temperature sensitive mechanism occurs either translationally or rotationally.

More preferably still, of the type of movement chosen (translational or rotational), the axis about which movement occurs is substantially parallel with the axis of the remaining available movement not chosen.

Still more preferably, the movement of the air control valve caused by the temperature sensitive mechanism occurs rotationally.

Preferably, when the air control valve re-adjusts its position, once the firebox has reached the second pre-determined temperature it does so by returning to its original position or to a position set by an operator.

Of the many types of temperature sensitive mechanism that could be used, for example trapped fluid expanding and operating bellows, preferably, the temperature sensitive 15 mechanism includes a bimetallic catch or strip.

The invention includes within its scope a solid fuel burner substantially as herein described with reference to and as illustrated in figures 1 to 8 of the accompanying drawings.

The invention further includes within its scope a solid fuel burner incorporating typical fuel to operate the burner.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention will now be more particularly described by way of example only, with reference to the accompanying sheets of drawings wherein: Figure 1 illustrates a partial perspective view of a solid fuel burner incorporating a translationally and rotationally operable air control valve fitted directly to a firebox 25 according to one preferred form of the invention, 130793NZ_SP_CAP spec.doc/CA/SP Figure 2 illustrates sectional views of the aspect of the burner illustrated in figure 1 showing the air control valve rotating to a fully open position as a result of the operation of a bimetallic catch preventing return to a closed position according to one preferred form of the invention, Figure 3 illustrates a part-sectional view of an alternative embodiment of the present invention with the air control valve biased against the burner according to one preferred form of the invention, Figure 4 illustrates the view of figure 2 but with the air control valve rotated to a fully open position as a result of the operation of a burner door opening and a bimetallic catch 10 preventing a return of the air control valve to a closed position according to one preferred form of the invention, Figure 5 illustrates a perspective part-sectional view of the bimetallic catch referred to in figures 3 and 4 according to one preferred form of the invention, Figure 6 illustrates a perspective view of a solid fuel burner incorporating the housing 15 shown in figures 3 to 5 and showing a partial cut away of the air control valve according to one preferred form of the invention, Figure 7 illustrates a cross-sectional view of a temperature sensitive mechanism at the higher pre-determined temperature according to one preferred form of the invention, Figure 8 illustrates a cross-sectional view of a temperature sensitive mechanism at the lower 20 pre-determined temperature according to one preferred form of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 illustrates a steel solid fuel burner generally referenced 1 containing a wood fire and comprising a door containing firebox 2 provided with three linearly spaced apart parallel substantially oblong apertures 3 each of whose longitudinal axis are substantially coincident. 25 The distance between each aperture 3 is at least the length of an aperture 3.

The burner 1 further comprises an air control valve 4 in the form of a substantially flat steel oblong plate of dimensions slightly greater than the height of each aperture 3 and slightly 130793NZ_SP_CAP spec.doc/CA/SP longer than the length swept out by the distance between opposing ends of the two furthermost apertures 3. The air control valve 4 is shown as a partial cut away, that is, its entire length is not shown.

The valve 4 is provided with an identical number of similarly sized apertures 5 as those 5 apertures 3, located on the firebox 2. The valve 4 sits on a ledge which projects from slightly below the apertures 3 and at substantially 90 degrees from the plane of the apertures 3. The valve 4 is designed to be horizontally slidable (within a runner (not illustrated) set in the ledge) along its longitudinal axis between two fixed positions. The extent of the first fixed position allows each of the apertures 5 to respectively completely overlie each of the 10 apertures 3 and the extent of the second fixed position has all except one of the terminally located apertures 5, overlying the spaces between the apertures 3. One of the terminally located apertures 5 will sit beyond the line of apertures 3.

In addition, the valve 4 is rotatable about the runner at any position along its length of travel between its two fixed positions but in the preferred form of the invention is biased into the 15 position shown in Figure 4 by a biasing device such as a spring or a counter weight (not illustrated). Alternatively, the valve 4 is supported offset to its centre of gravity. The air control valve 4 is linked to the door (not illustrated) to the extent that when the door is opened, the air control valve 4 rotates or otherwise tilts away from the firebox 2 to expose the full extent of the apertures 3. Many mechanisms to effect such a door operable 20 connection are known to those skilled in the art. In one example the door may carry an arm 30 positioned such that the arm 30 returns the valve 4 to the position shown in Figure 3 when the door is closed, or after a delay as hereinafter described.

In one embodiment of the invention, a bimetallic catch 6 is fitted to the firebox in between two of the apertures 3 and just above their height and is designed to remain in a retracted 25 position clear of the top of the air control valve 4 (when the burner 1 is at a second predetermined high temperature) to the extent that slidable movement of the valve 4 between the two fixed positions is not impeded. The bimetallic catch 6 is also designed to bend towards the firebox 2 (when the burner 1 is at a first pre-determined low temperature) and the top edge of the valve 4. Given the available travel of the air control valve 4 and the 30 location of the bimetallic catch 6, it is clear that the latter is so located on the firebox 2 that it will always be free of the top of the air control valve 4, or, at low temperatures, exert 130793NZ_SP_CAP spec.doc/CA/SP minimal downward pressure on the air control valve 4, thus still allowing free translational movement of the air control valve 4 from any starting position relative to the firebox 2.

Referring to figure 3, this illustrates the air control valve 4 biased against the firebox 2, but showing aperture 5 in line with aperture 3 of the burner 1 (the arrows showing the direction of air entry into the burner 1, said air flow being deflected by baffle 7 to behind a glass panel 9, forming part of a door 8, 10 of the burner 1). Again, the air control valve 4 operates in a similar manner as before and is operatively connected to the door opening mechanism (not illustrated) to tilt or otherwise rotate away from its biased position against the firebox 2 about its lower edge.

In another embodiment of the invention a substantially oblong box housing 11 is located above the air control valve 4. The longest side of the housing 11 preferably lies substantially parallel with the top edge of the air control valve 4. The housing 11 for all intents and purposes is maintained at the same temperature as the exterior wall of the firebox 2, by conduction. In the particular embodiment as depicted in Figure 5, the housing 11 contains a substantially "U" shaped bimetallic catch 12, the "U" shape lying on its side, with the curve towards the left hand side of the housing 11, when the burner 1 is viewed "face on". The dimensions of the bimetallic catch 12 are such that its width is substantially equal to the internal width of the housing 11 and that the lower edge of the bimetallic catch 12 terminates in a lip 13 that protrudes from a slot in the lower longest side of the housing 11. This lip 13 is so located as to sit within the housing 11 at a second pre-determined high temperature and protrude through the slot at a first pre-determined low temperature to ride on the top edge of the air control valve 4 (to the extent that translational movement of the air control valve 4 is not impeded) or fall behind it if the air control valve 4 rotates or tilts away from the firebox 2 as shown in figure 4.

In use, when the door 8, 9, 10 of the burner 1 is not opened and the temperature of the firebox 2 falls below the first substantially pre-determined temperature (because for example the fire has gone out), the bimetallic catch 6, will bend from its retracted position from within the housing 11 and simply ride upon a top edge of the air control valve 4. From this position, if the door 8, 9, 10 is opened, with the consequence that the air control valve 4 is 30 rotated or otherwise tilted away from the firebox 2 about the runner, then the bimetallic catch 6 will drop behind the air control valve 4 preventing the return of the air control valve 4 to its 130793NZ_SP_CAP spec.doc/CA/SP • 10 original position until the temperature of the burner 1 has risen sufficiently (that is, to equal to or above the second substantially pre-determined temperature) for the bimetallic catch 6 to bend upwards and away from behind the air control valve 4. The biasing device (not illustrated) will then cause or allow the air control valve 4 to return to its original position.

Alternatively, if the door 8, 9, 10 is opened to load more wood, there will be an initial drop in the temperature of the burner 1 as heat escapes through the door 8, 9, 10. This drop in temperature will cause the bimetallic catch 6 to bend in a similar way as described above to cause the same effect.

In a similar manner, the lip 13 is designed to remain in a retracted position clear of the top of 10 the air control valve 4 until temperatures fall below the required level (that is, to equal to or below the first substantially pre-determined temperature), where it moves as a result of the fall in temperature and rests or rides upon the top edge of the air control valve 4. From this position, if the door 8, 9, 10 is opened, with the consequence that the air control valve 4 is rotated or otherwise tilted away from the firebox 2 about the runner, then the lip 13 of the 15 bimetallic catch 12 will drop behind the air control valve 4. Upon an adequate rise in temperature, the lip 13 will retract back into the housing 11 and away from behind the air control valve 4. The biasing device (not illustrated) on the air control valve 4 will then cause or allow the air control valve 4 to return to its original position.

When the door is closed, the air control valve 4 will remain in its fully open position until 20 sufficient amounts of air have entered the burner 1 through the apertures 3 to cause the temperature of the burner 1 to rise back up to a second substantially pre-determined high temperature causing the bimetallic catch 6 or lip 13 to return to its original position above the air control valve 4. The biasing device (not illustrated) then serves to move the air control valve 4 back against the firebox 2. The construction of the bimetallic catch 6 is such that it 25 exhibits the required amount of movement to enable performance of the above function over a specified temperature range.

In an alternative embodiment, as depicted in Figures 7 and 8, the housing 11 may contain three components which together are adapted to perform the same function as described above. The three components include a bimetallic strip 14, a leverage means 15 and a latch 30 member 16. 130793NZ_SP_CAP spec.doc/CA/SP One end of the bimetallic strip 14 is attached to the internal surface of the upper longest side of the housing 11. The bimetallic strip 14 then bends about a pivot point such that its other end protrudes downwards into the housing 11 and is designed to exert a downward pressure on at least part of the leverage means 15. At a second substantially pre-determined high 5 temperature (for example, substantially 280 degrees Celsius) the bimetallic strip 14 bends into a first position (as shown in Figure 7). The first position may be for example on an angle of substantially 130 degrees. At a first substantially pre-determined low temperature (for example, substantially 250 degrees Celsius) the bimetallic strip 14 bends into a second position (as shown in Figure 8). The second position may be for example on an angle of 10 substantially 100 degrees. This temperature dependent rotational movement of the bimetallic strip 14 then converts into a rotational movement of the leverage means 15 as described hereafter.

The leverage means 15 as depicted is substantially V-shaped with extensions at each end. The leverage means 15 is pivotally mounted within the housing at the base of the V-shape 15 such that when the bimetallic strip 14 is in the first position, it exerts a downwards pressure on the left hand extension of the leverage means 15 such that the right hand extension of the leverage means 15 is forced upwards. When the bimetallic strip 14 is in the second position it exerts a downward pressure on the right hand extension of the leverage means 15 such that the left hand extension of the leverage means 15 moves upwards. This pivotal movement of 20 the leverage means 15 in turn converts into a translational movement of the latch member 16 as described hereafter.

The latch member 16 is an elongated preferably metallic strip which is located at one end of the housing 11 and is moveably attached to the housing 11 by extending through two slots in the upper and lower longest sides of the housing 11 respectively. The latch member 16 has a 25 stop at each end thereof which serves to hold the latch member 16 within the housing 11. The dimensions of the latch member 16 are such that its width is substantially equal to the internal width of the housing 11 and its length is greater than the length of the shortest side of the housing 11 such that the latch member 16 protrudes from either one of the slots in the housing 11 depending on the extent of its translational movement. The latch member 16 has 30 a U-shaped bend at a selected position along its length which is designed to rest on the right hand extension of the leverage means 15 thereby serving as a means by which the latch member 16 is translationally moved within the housing 11. 130793NZ_SP_CAP spec.doc/CA/SP Thus in use, when the temperature of the firebox 2 falls below the first pre-determined low temperature (because for example the door is opened for refuelling), the bimetallic strip 14 will bend from its first position into its second position causing the leverage means 15 to move downwards and thereby lowering the latch member 16 such that the end of the latch 5 member 16 protrudes through the slot in the lower longest side of the housing 11 and rides upon the top edge of the air control valve 4. From this position, if the door 8 ,9, 10 is opened, with the consequence that the air control valve 4 is rotated or otherwise tilted away from the firebox 2 about the runner, then the latch member 16 will drop behind the air control valve 4 preventing the return of the air control valve 4 to its original position until the 10 temperature of the burner 1 has risen sufficiently (that is, to the second pre-determined temperature) for the bimetallic strip 14 to bend back into its first position causing the leverage means 15 to move upwards and thereby raising the latch member 16. In its raised position, the latch member 16 is designed to remain in a retracted position clear of the top of the air control valve 4 (such that movement of the air control valve is not impeded). The arm 15 30 on the door, which in this embodiment is a resilient arm 30 which could be part of a coil spring 31 mounted to the door by pivot anchor 32, is therefore allowed to move the valve 4 against its biasing device to the closed position. The arm 30 is resilient so that the door may fully close whilst the valve 4 is in the position shown in Figure 4. Thus the resilience of the door mounted arm 30 must be sufficient to overcome the biasing of the valve 4 to its open 20 position.

Therefore when the door is closed, the air control valve 4 will remain in its fully open position until sufficient amounts of air have entered the burner 1 through the apertures 3 to cause the temperature of the burner 1 to rise back up to a sufficient pre-determined level causing the bimetallic strip 14 to return to its first position and hence moving the latch 25 member 16 to its retracted position above the air control valve 4.

The invention is used as is apparent from the above description.

Thus it can be seen that at least in the preferred form of the invention a solid fuel burner is provided which will admit air, even when the air control mechanism is fully closed, when the door of the burner is re-closed after it is opened, for example, for refuelling. This will 30 encourage higher operating temperatures of the burner and therefore aid in the reduction of emissions. 130793NZ_SP_C AP spec.doc/CA/SP Throughout the description and claims of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps. 130793NZ_SP_CAP spec.doc/CA/SP

Claims (16)

-13- WE CLAIM:

1. A solid fuel burner comprising the following components: a firebox having a door and at least one aperture therein for air flow purposes; an air control valve capable of adjustment with respect to the firebox to regulate the rate of flow of air into the firebox, said adjustment being functionally linked to the opening and closing mechanism of the door; a temperature sensitive mechanism adapted to firstly, automatically adjust its position relative to the air control valve when the firebox falls below a first substantially predetermined temperature and to secondly, automatically re-adjust its position relative to the air control valve once the firebox has reached a second higher substantially predetermined temperature; wherein their arrangement is such that once the door is opened thereby causing a drop in the temperature of the burner to the first pre-determined temperature, the air control valve is prevented from readjustment upon door closure by the temperature sensitive mechanism, until the second pre-determined temperature has been reached.

2. A solid fuel burner as claimed in claim 1 wherein the air control valve comprises a plate having a selected number of apertures therein which correspond in number and position to the aperture or apertures located on the firebox.

3. A solid fuel burner as claimed in claim 1 or claim 2 wherein the air control valve is directly or indirectly connected to the firebox.

4. A solid fuel burner as claimed in any one of the preceding claims wherein adjustment of the air control valve can occur by translational movement of the air control valve with respect to the firebox.

5. A solid fuel burner as claimed in any one of the preceding claims wherein adjustment of the air control valve can occur by rotational movement of the air control valve with respect to the firebox. 130793NZ_SP_CAP spec.doc/CA/SP -14-

6. A solid fuel burner as claimed in any one of the preceding claims wherein the air control valve is biased by a biasing device such as a spring or a counter weight.

7. A solid fuel burner as claimed in any one of the preceding claims wherein the air control valve is supported offset to its centre of gravity. 5

8. A solid fuel burner as claimed in any one of the preceding claims wherein the temperature sensitive mechanism is operatively associated with the air control valve at all times.

9. A solid fuel burner as claimed in any one of the preceding claims wherein the temperature sensitive mechanism includes a bimetallic catch or strip.

10 10. A solid fuel burner as claimed in any one of the preceding claims wherein the temperature sensitive mechanism is provided within a housing located on the firebox above the air control valve.

11. A solid fuel burner as claimed in any one of the preceding claims wherein the temperature sensitive mechanism includes a bimetallic strip, a leverage means and a 15 latch member.

12. A solid fuel burner as claimed in claim 10 wherein the bimetallic strip causes pivotal movement of the leverage means, which in turn causes translational movement of the latch member to substantially prevent readjustment of the air control valve until the firebox reaches the second pre-determined temperature. 20

13. A solid fuel burner as claimed in any one of the preceding claims wherein the movement of the air control valve caused by the temperature sensitive mechanism occurs translationally and/or rotationally.

14. A solid fuel burner as claimed in any one of the preceding claims wherein the air control valve re-adjusts its position by either returning to its original position or to a 25 position set by an operator, once the firebox has reached the second pre-determined temperature. "Intellectual pworemr iwk Of n.z. t 5 AUG 2005 RECEIVED 130793NZSPCAP spec.doc/CA/nk -15-

15. A solid fuel burner as claimed in any one of the preceding claims wherein the door includes a resilient arm thereon which is capable of moving the air control valve against its biasing device into the closed position.

16. A solid fuel burner substantially as herein described with reference to the accompanying drawings. END OF CLAIMS v PIPERS Attorneys for WERNER JOHANNES JANSSENS 130793NZ_SP_CAP spec.doc/CA/SP