Abstract:
A gas hearth including a combustion chamber, a gas supplier for supplying combustible gas into the combustion chamber to a firebed simulator disposed in the combustion chamber, an ignitor for igniting the combustible gas in the combustion chamber, a flue-gas discharge duct connected to the combustion chamber for discharging combustion flue gases from the combustion chamber, and a metering means disposed in the combustion chamber for metering a pyrotechnical additive into the flames of the burning combustible gas during operation.

Description:
TECHNICAL FIELD AND BACKGROUND 
       [0001]    The invention relates to a gas hearth including a combustion chamber, a gas supplier for supplying combustible gas into the combustion chamber to a firebed-simulator positioned in the combustion chamber, an ignitor for igniting the combustible gas in the combustion chamber and a flue-gas discharge duct connected to the combustion chamber for discharging combustion flue gases from the combustion chamber. 
         [0002]    Various types of hearths, in particular decorative hearths, are known and can be used as built-in hearths or as hearth stoves. Such decorative hearths are suitable for burning gas, wood or other natural fuels. A decorative hearth which is known from, for example, from EP1659340A2, tries to produce a fire image which is as realistic as possible and is characterized by firebed-simulating means which are made up as imitation logs which are provided with lighting elements. 
         [0003]    The lighting elements which are present in the imitation logs emit light which gives the impression that the imitation log is burning. However, such decorative hearths in which the fire image is only based on lighting elements do not give a realistic impression of a fire. 
         [0004]    Other decorative hearths are known, wherein firebed-simulating means in the form of imitation logs positioned over a real firebed have been placed in the combustion chamber. This firebed is produced by means of gas supply means which extend into the combustion chamber and by means of which gas along and around the imitation logs is ignited. This creates the impression as if the imitation logs are actually burning. The combustible flue gases are then discharged via a flue-gas discharge duct which is connected to the combustion chamber. 
         [0005]    However, the problem associated with these gas hearths is that a relatively high supply of gas is required to achieve a firebed or flame bed which is sufficiently large as to create a realistic impression of a fire. As a result thereof, a significant amount of heat and energy is lost. Since the primary aim of a decorative hearth is to imitate a firebed and thereby to create an impression of a fire, producing heat is a secondary aim, thus it is desirable for a gas hearth to have a gas and energy consumption which is as minimal as possible. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    It is therefore an object of the present invention to provide a gas hearth according to the abovementioned preamble that provides a realistic impression of a fire while using a minimal amount of natural fuel. 
         [0007]    To this end, the gas hearth is provided with metering means arranged in the combustion chamber for metering a pyrotechnical additive into the flames of the burning combustible gas during operation. This makes it possible to produce an additional fire impression, for example, sparks which also occur with the burning of real wooden logs. 
         [0008]    More specifically, the metering means includes a reservoir for the pyrotechnical additive which is provided with at least one metering opening, and furthermore at least one supply line which is connected to the metering opening and ends near the firebed simulator. To this end, it is possible to install the metering means elsewhere in the gas hearth and not necessarily in the combustion chamber, which is not desirable from an aesthetic and safety point of view. 
         [0009]    According to a further aspect, the metering means includes at least one pump which is placed near the at least one metering opening for passing a certain amount of pyrotechnical additive through the supply line in the direction of the firebed simulator by means of a pressurized medium. 
         [0010]    More particularly, the metering means includes a valve arranged for closing the at least one metering opening and for dispensing a certain amount of pyrotechnical additive from the reservoir and the metering means includes control means for actuating the valve and the pump, in particular, for sequentially actuating the valve and the pump. In this way, it is possible to add the pyrotechnical additive to the flame bed in a quick and safe manner by means of a simple actuation in order to produce an additional, more realistic impression of a fire. 
         [0011]    In one aspect, the valve is a magnetic coil-actuated valve and the pump is a compressed air pump. 
         [0012]    The metering means may be arranged under or above the firebed simulator. 
         [0013]    In the latter embodiment, the reservoir can be attached to a shaft, and the metering means can include drive means for rotatably driving the shaft. 
         [0014]    In one aspect, the drive means can be configured as a chain drive. 
         [0015]    In a further embodiment, the reservoir can be provided with a filling opening which can be closed with a closure, which closure, in the embodiment wherein the metering means have been arranged under the firebed simulator means, forms part of the firebed simulator. 
         [0016]    In particular, the reservoir can be configured to pass the pyrotechnical additive to the at least one metering opening. Thus, the metering means can require very little, if any, maintenance and the risk of failures and/or blockages is minimal. 
         [0017]    In this case, the reservoir may be provided with one or more walls which run at an angle in the direction of the at least one metering opening. 
         [0018]    Furthermore, the pyrotechnical additive may include granules, for example a pulverulent or granular material, in particular a carbon-containing additive. 
         [0019]    Embodiments of the invention can include one or more or any combination of the above features and configurations. 
         [0020]    Additional features, aspects and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein. It is to be understood that both the foregoing general description and the following detailed description present various embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    These and other features, aspects and advantages of the present invention are better understood when the following detailed description of the invention is read with reference to the accompanying drawings, in which: 
           [0022]      FIG. 1  shows a diagrammatic view of a gas hearth according to the prior art with a metering means according to the present invention; 
           [0023]      FIG. 2  is a perspective view of a metering means and hearth according to an embodiment of the invention; 
           [0024]      FIG. 3  is an elevation view of the metering means; 
           [0025]      FIG. 4  is a cross-sectional view of the metering means; 
           [0026]      FIG. 5  is a perspective view showing the metering means, pump, and controller; 
           [0027]      FIG. 6  is an exploded view of another embodiment of a metering means; 
           [0028]      FIG. 7  is an assembled perspective view of the metering means of  FIG. 6 ; and 
           [0029]      FIG. 8  is a detailed view of a portion of the hearth according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    For a better understanding of the invention, the similar components shown in the various figures are denoted by identical reference numerals in the following description of the figures. 
         [0031]      FIG. 1  diagrammatically shows an embodiment of a gas hearth according to the prior art. In particular, the burner system of a hearth is shown in the way in which it is arranged in the combustion chamber of the gas hearth. 
         [0032]    In general, a decorative hearth is composed of a housing comprising side walls, a bottom wall, a front wall and a rear wall. The front wall is often transparent and can also be rotated away or slid away for maintenance. The front, bottom, rear and side walls enclose a combustion chamber  10  in which the firebed-simulating means, denoted here, for example, by reference numerals  12   a - 12   d,  are accommodated. The firebed-simulating means  12   a - 12   d  are configured to simulate a fire image and all respective components are fitted to a bottom panel which forms part of the bottom wall of the combustion chamber  10 . 
         [0033]    As is illustrated in  FIG. 1 , the hearth  1  is provided with gas supply means (gas supply line)  13  which are connected to a main supply line (not shown). The gas supply line  13  branches off into branch lines  13   a - 13   d,  each of which extend into the combustion chamber  10 , and which, in particular, each end at the location of the firebed-simulating means  12   a - 12   d.  A control valve  14  is incorporated in the gas supply line  13  which can be controlled by suitable control means (not shown) via the control line  15  and can be closed off in order to close off the gas supply into the combustion chamber  10 . 
         [0034]    The firebed-simulating means  12   a - 12   d  may be configured, for example, as imitation logs, which may, for example, be made of a fireproof ceramic material. Such imitation logs are often also porous, so that the gas supplied via the respective branch line  13   a - 13   d  may flow through or leak into the porous imitation logs and can be made to ignite locally on the surface using suitable, gas ignition means (not shown). In this way, a fire image may be simulated which is similar to that of a conventional fire of burning wooden logs. 
         [0035]    The combustion flue gases can be discharged from the combustion chamber  10  via the flue-gas discharge duct  11 . 
         [0036]    As one objective of a decorative hearth is to produce a realistic fire image, and is not intended, unlike conventional hearths, to emit heat to the surroundings, it is desirable for a decorative hearth to produce as realistic a fire image as possible while using a minimal amount of gas. 
         [0037]    However, a lower gas consumption (i.e. gas supply to the combustion chamber via the gas supply  13 ) also leads to fewer flames, as a result of which the fire image is less realistic. However, the firebed-simulating means  12   a - 12   d  aim to enhance the fire image by simulating burning logs. 
         [0038]    In order to be able to also produce a realistic fire image with an improved fire impression in the case of reduced gas consumption, metering means  20  are arranged in the combustion chamber  10  which, during operation, meter a pyrotechnical additive into the flames of the burning combustible gas. In particular, the metering means are arranged above the firebed-simulating means  12   a - 12   d,  as is illustrated in  FIG. 1 , in such a way that, when metering the pyrotechnical additive being contained in reservoir  22  via the metering opening  22   b,  this additive ends up in the air stream of the rising combustible flue gases and is ignited by the flames when it flutters down in the direction of the firebed created by the firebed-simulating means  12   a - 12   d . Upon ignition, the pyrotechnical additive generates additional fire and light effects, such as sparks, which also occur during burning of natural wooden logs. 
         [0039]    In another embodiment, such as illustrated, for example, in  FIG. 5 , the metering means  20  are arranged at the bottom of the combustion chamber  10  and more particularly under the firebed-simulating means  12   a - 12   d.    
         [0040]    The metering means  20  are composed of a mounting panel  21  to which, and on which, all relevant components are attached. Reference numeral  22  indicates a reservoir wherein a certain amount of pyrotechnical additive is stored. The reservoir  22  is sufficiently fire-resistant and heat-resistant in order to ensure that the heat which is produced in the combustion chamber during operation does not result in an undesirable and premature spontaneous combustion of the pyrotechnical additive which is held in the reservoir  22 . 
         [0041]    The reservoir  22  is provided with a top side  22   a  which is provided with an opening which may be closed off by a closure, in particular a closing lid  23 . The reservoir  22  can be filled with a certain amount of pyrotechnical additive via the opening which is provided in the top side  22   a.  Furthermore, the reservoir  22  is provided with a metering opening  22   b  for supplying a certain amount of pyrotechnical additive from the reservoir  22  to a supply line  25  which runs from the metering opening  22   b  through the combustion chamber and the free end  25   a  of which ends at one of the firebed-simulating means  12   a - 12   d,  as is illustrated in  FIG. 1 . 
         [0042]    The reservoir  22  is constructed in such a way that it promotes or facilitates the supply of the pyrotechnical additive from the reservoir  22  in the direction of the metering opening  22   b  and the supply line  25 . In particular, the reservoir  22  is provided with oblique walls  22   c  and  22   d  which thus form a funnel in the direction of the metering opening  22   b.    
         [0043]    According to the invention, the metering opening  22   b  can be closed off by means of a controllable shut-off valve  24 . By briefly opening and closing the closable valve  24 , a certain amount of pyrotechnical additive can leave the reservoir  22  via the metering opening  22   b  closed off by the valve  24  and be received in the line  25 . At the location of the closable valve  24 , the line  25  is connected to an air line  27  which is connected to a pump  26 . By means of the pump  26 , the amount of pyrotechnical additive held in the line  25  by means of a pressurized medium, for example air, can be blown in the direction of the outlet opening  25   a.    
         [0044]    When the pyrotechnical additive leaves the outlet opening  25   a,  which, as has already been mentioned, is positioned at the location of the firebed-simulating means  12   a - 12   d,  it will come into contact with the burning gas and thus create additional flame and fire effects, such as sparks. 
         [0045]    To this end, the metering means  20  also comprise control means  28  (see  FIG. 3 ) which pass control signals to the closable control valve  24  or the pump  26 , respectively, via suitable control lines  29   a  and  29   b.  More specifically, the control means  28  are configured in such a way that the control means actuate the control valve  24  and the air pump  26  sequentially. Sequentially means firstly that the closable control valve  24  is actuated by the control means  28 , resulting in the control valve  24  being opened briefly. As a result thereof, a certain amount of pyrotechnical additive can be poured or metered into the line  25  from the reservoir  22  via the metering opening  22   b  which has been opened in this way. 
         [0046]    Subsequently, the control valve  24  is closed by the control means  28  and the air pump  26  is actuated which blows this metered amount of pyrotechnical material through the supply line  25  in the direction of the outlet opening  25   a  by means of a short air pressure pulse via the air line  27  and the supply line  25 . Upon leaving the outlet opening  25   a  on account of the air pulse delivered by the pump  26 , the dispensed pyrotechnical additive will be brought to ignition at the location of the firebed-simulating means  12   a - 12   d  (see  FIG. 1 ) by the burning gas and thus produce the additional flame and fire effects. 
         [0047]    The air pump  26  is in each case actuated briefly by the control means  28  for delivering an air pressure pulse in the air line  27  in the direction of the control valve  24  and the supply line  25 . To this end, the air pump  26  takes air from elsewhere and preferably from outside the combustion chamber  10  (see  FIG. 1 ) via the inlet opening  27   a.  Thus, the air line  27  has such a length, as a result of which the air pump  26  and preferably the inlet opening  27   a  are arranged at some distance from and outside the combustion chamber  10 . This prevents hot combustion flue gases from being introduced into the air line  27  via the inlet opening  27   a,  which could possibly cause the pyrotechnical additive metered into the supply line  25  to ignite spontaneously. The position of the inlet opening  27   a  of the air line  27  as far as outside the combustion chamber  10  is thus a safety aspect of the present gas hearth. 
         [0048]    In this embodiment, a non-return valve has to be incorporated in the inlet line  27   a  which extends to the outside of the combustion chamber in order to prevent combustion flue gases from escaping from the combustion chamber  10  via the air line  27  and the inlet opening  27   a  instead of via the flue-gas discharge duct  11 . 
         [0049]    In a preferred embodiment, the inlet opening  27   a  of the air line  27  and the outlet opening  25   a  of the outlet line  25  are both in the combustion chamber  10 . This results in a closed system, so that combustion flue gases cannot escape from the combustion chamber except via the flue-gas discharge duct  11 . However, the inlet opening  27   a  has to be arranged in the combustion chamber  10  in such a way, for example at some distance from the firebed-simulating means, so as to prevent an undesired inflow of combustion flue gases. 
         [0050]    In yet another embodiment, the air pump is not switched on or off by the control means  28 , but the air pump is actuated continuously and an air stream is continuously blown in the direction of the supply line  25  and the outlet line  25   a  by the air line  27 . 
         [0051]    As is illustrated in  FIG. 4 , the closable control valve  24  is, in particular, a magnetic valve (also referred to as a magnet-coil actuated valve). To this end, the control valve  24  is provided with a bore hole  24   b  in which a reciprocating plunger  24   a  is accommodated. The plunger  24   a  is movable into a closed position, such as illustrated in  FIG. 4 , in which it closes the metering opening  22   b  and closes it off from the air line  27  and the supply line  25 , and into an open position, in which the metering opening  22   b  is briefly connected with the supply line  25 , so that pyrotechnical additive which is situated in the reservoir  22  can be metered out. 
         [0052]    The reciprocating plunger  24   a  is provided with grooves wherein coil windings  24   c  are wound. In addition, the valve  24  is provided with a magnet  24   e  which is arranged around the bore hole  24   b  and the part of the plunger  24   a  where the coil windings  24   c  are situated. By means of suitable control signals which are emitted by the control means  28  to the magnetic valve  24  via the control line  29   a,  the plunger  24   a  can be moved to and fro in the bore hole  24   b  between the closed position and the open position on account of the coil/magnet interaction. 
         [0053]    In this way, it is possible to transfer a small amount of pyrotechnical additive from the reservoir and the open metering opening  22   b  to the supply line  25  by in each case briefly opening the magnetic valve  24 . Closing the magnetic valve  24  again first and then actuating the air pump  28  to deliver an air pulse into the air line  27  prevents the air pulse from blowing the pyrotechnical additive which has just been metered back into the reservoir  22 . By contrast, the closed magnetic valve  24  causes the metered pyrotechnical additive which is present in the supply line  25  to be blown in the direction of the outlet opening  25   a  by the air pulse through the supply line  25 . 
         [0054]    Preferably, the actuation of the magnetic valve  24  by the control means  28  is random, so that the supply of the pyrotechnical additive via the outlet opening  25   a  to the burning firebed-simulating means  12   a - 12   d  is also random and unpredictable. The random unpredictable actuation of the magnetic valve  24  and the resulting random supply of pyrotechnical additive to the firebed-simulating means  12   a - 12   d  also contributes to a more realistic fire image, since this also produces random flame and fire effects, similar to the fire image of a conventional burning log fire. 
         [0055]    The time period of the brief opening of the magnetic valve  24  may also be set randomly within a certain range, so that the amount of pyrotechnical additive during each metering from the reservoir  22  in the supply line  25  also varies. Consequently, the intensity of the resulting flame and fire effects vary with each dose. This also helps to create an improved simulation of the random and chaotic fire image of a conventional burning log fire. 
         [0056]    The pyrotechnical additive preferably includes granules, in particular a pulverulent or granular material. In particular, the pyrotechnical additive is a carbon-containing additive, in which the granules have a grain size of between 0.05 mm-2.5 mm. 
         [0057]    In a further embodiment, such as illustrated in  FIG. 5 , wherein the metering means  20  are positioned under the firebed-simulating means  12   a - 12   d  of the gas hearth, as is illustrated in  FIG. 1 , the closure  23  is formed in such a manner that it fauns part of the firebed-stimulating means. In  FIG. 5 , the closure is denoted by reference numeral  230  and is formed as an imitation log. In this way, the metering means  20  can be fitted at a small distance below the level of the firebed-simulating means  12   a - 12   d  in the gas hearth, thus achieving a further reduction in the installation space. 
         [0058]    It should be noted that although the sealing cap  230  is formed as an imitation log, it does not actively contribute to the play of flames and fire during operation. The sealing cap  230  will therefore not be porous and will also not be provided with a connection to the gas supply means  13 , as illustrated in  FIG. 1 . 
         [0059]      FIGS. 6-8  show another embodiment of a gas hearth according to the invention. 
         [0060]    In this embodiment, the metering means  40  are positioned at the top of the combustion chamber  10  and in particular above the firebed-simulating means  12   a - 12   d.  The reservoir  42  is provided with a top side  42   a  in which an opening  42   a ′ is provided which can be closed off by a closure, in particular a closing lid or cap  43 . The reservoir  42  can be filled with a certain amount of pyrotechnical additive via the opening  42   a ′ which is provided in the top side  42   a.    
         [0061]    Furthermore, the reservoir  42  is provided with one or more metering openings  42   b  for supplying or scattering a certain amount of pyrotechnical additive at the top of the combustion chamber  10  (and above the burning firebed-simulating means  12   a - 12   d ) from the reservoir  42 . In this case, the reservoir  42  is placeable in a holder  41  which is supported by shafts  45  which are rotatably accommodated in the combustion chamber  10  (see  FIG. 8 ). In this case, reservoir  42  is retained in the holder  41  by means of a retaining pawl  44   a  which can be fixed to the threaded end  41   c  of the holder  41  by means of a swivel or screw  44   b.    
         [0062]    Analogous to the reservoir  22  as shown in  FIGS. 2-6 , the reservoir  42  has oblique walls  42   c  and  42   d  which thus form a funnel in the direction of the metering opening  42   b  in order thus to assist or facilitate the supply of the pyrotechnical additive to the combustion chamber  10 . 
         [0063]    Furthermore, the metering means  40  comprise drive means  50  for rotatably driving the shaft  45 . The drive means  50  are placed on one side of the combustion chamber  10  and in this embodiment comprise a drive motor  51  (electric motor) provided with a first gear wheel  53   a  by means of which the shaft  45  is rotatably driven via a chain transmission. To this end, a chain  52  is placed over the first gear wheel  53   a  and also runs across a second gear wheel  53   b.  The second gear wheel  53   b  is placed on the shaft  45 . On the other side of the combustion chamber  10 , the shaft  45  is mounted in a bearing  46  which is accommodated in the wall of the combustion chamber  10 . 
         [0064]    In operation, the drive motor  51  will rotate the shaft  45 , as a result of which the holder  41  with the reservoir  42  in the combustion chamber  10  and above the firebed-simulating means  12   a - 12   d  co-rotate. With each rotation, the pyrotechnical additive in the reservoir  42  will be displaced in the direction of the metering opening(s)  42   b  (partly assisted by the oblique side walls  42   c  and  42   d ) and will be released into the top of the combustion chamber  10  and above the burning firebed-simulating means  12   a - 12   d  (see  FIG. 1 ) via the metering opening(s)  42   b  on account of the force of gravity. 
         [0065]    The pyrotechnical additive will enter the air stream of the rising combustible flue gases and will be ignited by the flames when it drifts down in the direction of the firebed created by the firebed-simulating means  12   a - 12   d.  Upon ignition, the pyrotechnical additive creates additional fire and light effects, such as sparks, which also occur during burning of natural wooden logs. 
         [0066]    Instead of performing a complete rotation, the reservoir  42  may also be rotated to and fro by the drive motor  51 . Upon each rotation or reciprocating movement, the pyrotechnical additive in the reservoir  42  will be disturbed and will be released in the form of a small dose of a random amount of additive via the metering opening  42   b.