Valve and a heating apparatus comprising such valve

Description

[0001] The invention relates to a valve according to the preamble of claim 1.

[0002] Such a valve is known from European patent application EP-A-0 400 757. This known valve is intended to create a controlled minimum air flow in the combustion chamber, so that a pilot flame does not go out for lack of oxygen and, moreover, no condensation occurs in the combustion chamber, while it is also effected that, owing to the presence of the valve, not unduly much heat is lost that is generated by the pilot flame and/or transmitted by the hot water in the heat exchanger to the air flowing past.

[0003] A problem involved in the known heating apparatuses is that of acoustic resonances caused by pressure variations in the combustion air duct, the fuel/air-mixture duct, the combustion chamber and/or the flue duct of the heating apparatus. In particular when the power of the heating apparatus can be modulated, for instance through variation of the speed of the fuel/air-mixture fan, the chance of resonances occurring is great. Such acoustic resonances occur in particular at the lower speed ranges of the fan, i.e. at a modulated burner power. Sources of the resonances are pressure variations created during the combustion process. These pressure variations are amplified through reflection in the heating apparatus with its inlet and outlet channel system, which together form a resonator. Particularly at low-load, the acoustic damping through resistance is small and the chance of resonances occurring is considerable. The resonance can be removed by providing additional acoustic damping by means of flow resistances in the inlet and/or outlet channel system. However, at full load of the installation, i.e. at a maximum fan speed, additional flow resistances are not acceptable, because they require more fan pressure than is generally available.

[0004] The resonance problem can be solved by providing a variable flow resistance in the inlet and/or outlet channel system. Examples hereof are motor-controlled valves known in different embodiments. However, such motor-controlled valves are costly because of the necessary drive and control.

[0005] An example of a motor controlled valve is shown in US-A-2,302,678. The valve is a draft damper comprising a draft or valve plate, which is pivotable between a open position and a closed position about a pivot, which pivot extends parallel to the valve plate and is positioned excentrically relative to the center of the valve plate. This is not an antiresonance valve but a balanced draft damper. In order to control the flow of atmospheric air into a breaching leading to a stack or the like, the known draft damper comprises a spring biasing the damper plate toward a closed position and comprises a motor and a transmission for varying the tension of the spring so as to control the draft. It should be noted that the damper of US-A-2,302,678 is not intended to be mounted in the fuel/air-mixture duct, the combustion air duct or the flue duct of a heating apparatus but into a breaching leading to a stack or the like. The breaching will lead some false air into the stack if the draft is strong, such that the draft in the heating apparatus will be reduced.

[0006] The valve discussed in the opening paragraph is controlled by gravity and the fan pressure. Gravity exerts a force on the valve, forcing the valve into a closed position. The valve moves to an open position under the influence of the fan pressure. If the fan pressure is maximal, the valve is in an entirely open position, and if the fan pressure decreases, the valve moves to the closed position until, at a given minimum fan pressure, the valve assumes the closed position under the influence of gravity.

[0007] A drawback of the valve controlled by gravity and the fan pressure is that such a valve should have an eccentrically arranged mass so that the gravity exerted thereby on the valve plate overcomes a given minimum fan pressure. As a consequence of the mass necessarily present, the known valve has a relatively great mass moment of inertia. A consequence of such great mass moment of inertia is that the valve may start to oscillate. This causes instabilities occurring in particular during pressure pulses which may for instance occur at the start of the fan or at a sudden gust of wind. The object of the invention is to provide a valve without the drawbacks of the known valves described hereinabove.

[0008] To this end, the valve described in the opening paragraph is characterized by the features of claim 1.

[0009] Because in a valve according to the invention, the closing moment on the valve plate is exerted by a spring, the valve plate can be of a particularly light construction, allowing the mass moment of inertia thereof to be minimized. A valve plate of such construction exhibits, during the use thereof, a minimum tendency to oscillate, so that the chance of instabilities and, accordingly, the occurrence of resonances, is minimized.

[0010] Because the spring is constructed or arranged so that the closing moment decreases according as the valve plate is pivoted further in the direction of the open position, the valve causes a minimum pressure loss during full-load of the burner, i.e. at the maximum speed of the fan. Moreover, these features are particularly favorable because the force exerted on the valve plate by the fuel/air-mixture flow, the combustion air flow or the flue gas flow, decreases at positions that are opened further, because the frontal surface of the valve plate decreases in these further-opened positions.

[0011] The invention also relates to a heating apparatus as characterized by the features of claim 8. Such heating apparatus has as its most important advantage that resonances are prevented therein without requiring a stronger fan than is usual. Moreover, the apparatus has the advantages already mentioned in the description of the valve.

[0012] Further elaborations of the invention are described in the subclaims and will be specified hereinafter with reference to the accompanying drawings, wherein:

Fig. 1 is a sectional view of an embodiment of the valve; and

Fig. 2 is a sectional view of a heating apparatus comprising a valve according to the invention.

[0013] The valve shown in Fig. 1 is intended to be fitted in a fuel/air-mixture duct, combustion air duct or flue duct of a heating apparatus having a modulating burner. A modulating burner is a burner capable of functioning both at full load and at a continuously variable part load, for instance through variation of the fan speed of the fan associated with the burner. Depending on the speed of the fan, more or less combustion air with an appropriate amount of fuel, such as for instance gas, is fed to the burner. The valve 1 comprises a valve plate 3 which is disposed in the duct 2 and which is pivotable between a closed position and an open position about a pivot 4. The pivot 4 extends parallel to the valve plate 3 and is positioned eccentrically relative to the center of the valve plate 3 and the duct 2 wherein the valve plate is located. As a result, the valve plate subsurface 3a extending on a first side of the pivot 4 is larger than a valve plate subsurface 3b extending on the other side of the pivot 4. The valve 1 is intended for minimizing resonances in the inlet and outlet channel system of the heating apparatus. For this purpose, in accordance with the invention, the valve 1 comprises a closing spring 5 adapted to exert a closing moment on the valve plate 3, causing it to be biased in a closed position. In order to minimize oscillations of the valve plate 3, the moment of mass inertia of the valve place 3 has been minimized.

[0014] By choosing the force required for holding the valve plate 3 in the open position to be as small as possible, it is effected that the loss of pressure caused by the presence of the valve is as small as possible. On the other hand, in the virtually closed position of the valve plate 3, the closing moment should be sufficiently great to create a sufficient pressure drop over the valve 1 for damping acoustic resonances and to limit oscillations of the valve in this position. To achieve this, in the present case, the spring 5 is arranged so that the closing moment decreases according as the valve plate 3 is pivoted further in the direction of the open position. In the present case, the decrease of the closing moment according as the valve plate 3 is pivoted further in the direction of the open position is realized by the specific arrangement of the spring. However, it is of course also possible that the spring is constructed in a specific manner.

[0015] In the present exemplary embodiment, the spring is a draw spring 5 having a first free end 5a attached to the smaller valve plate subsurface 3b and having a second free end 5b attached to a fixed point 6. The attachment is chosen so that the moment arm of the force acting on the valve plate 3, i.e. the distance between the pivot 4 and an imaginary line in the direction of which the force acts - in this case the center line of the spring -, decreases according as the valve plate 3 is opened further.

[0016] With a valve of such construction, it is achieved in a constructionally simple manner that the closing moment exerted on the valve plate 3 decreases according as the valve is opened further. Preferably, the closing moment exerted by the spring 5 in the open position of the valve plate 3 is virtually zero. In the present case, this is realized in that in the open position of the valve plate 3, the draw spring, constructed as helical spring 5, extends parallel to the valve plate surface, and in that in the open position of the valve plate 3, the center line of the helical spring 5 virtually intersects the center line of the pivot 4. It is understood that the center line of the helical spring 5 should not pass the center line of the pivot 4 during the opening of the valve, because otherwise the valve would slip into an undesired stable position and not return into the closed position anymore.

[0017] To enable the valve to be mounted in a simple manner, the valve 1 preferably comprises a valve sleeve 7 having substantially the same diameter as the duct 2 wherein the valve 1 is to be fitted. The pivot 4 can then be rotatably bearing-mounted in the valve sleeve 7 in a simple manner. Also, a fastening hook 6 can be mounted on the valve sleeve 7, which fastening hook provides the fixed point for attachment of the second end 5b of the draw spring 5.

[0018] Such a valve 1 having a valve sleeve 7 can be sold as a single unit and can readily be fitted in a fuel/air-mixture duct, combustion air duct or flue duct of a heating apparatus.

[0019] Preferably, the valve sleeve 7 also comprises a stop 8 against which the valve plate 3 abuts, in the closed position thereof. The stop 8 is provided to leave the valve plate 3 always sufficiently open at small gas flows (low load). The remaining opening prevents the occurrence of oscillations on account of unduly great relative changes in the passage, which great relative changes would indeed occur if the valve closed entirely or almost entirely.

[0020] Fig. 2 schematically shows, in section, a heating apparatus comprising a premix burner 9, a combustion air fan 10, whose outlet is connected, via a fuel/air-mixture duct 11, to a combustion space 12 with an associated heat exchanger 13. Downstream of the heat exchanger 13, a flue duct 14 is connected to the combustion space 12. In accordance with the invention, the apparatus comprises a valve 1 according to one of claims 1-8. The chance of resonances occurring in such a heating apparatus has been minimized, while it is also provided that owing to the low mass inertia of the valve plate, the chance of instabilities caused by pressure pulses, which may for instance occur during the start of the combustion fan or during a sudden gust of wind, is minimized.

[0021] Preferably, the valve 1 is arranged in the fuel/air-mixture duct 11 located upstream of the combustion space 12, because in this area, the temperature of the gas flowing along the valve 1 is low and, also, the gas does not contain any aggressive substances, such as for instance acids that may be released as a result of the combustion process.

[0022] When the valve 1 is being mounted, it is preferred that the velocity distribution of the gas flow in the duct 2 be taken into account. The valve should be positioned so that the large valve plate subsurface 3A is located on that side of the duct 2 where the flow rate of the gas is greatest.

[0023] Apart from the most important advantage of the valve according to the invention, viz. that resonances are prevented without requiring a stronger fan, the valve according to the invention provides a number of additional advantages:

1. The presence of the valve creates the conditions for controlling the burner in a larger power range without involving acoustic resonances or pulsations;

2. In low-load or a modulated operating range, the higher resistance in the duct, resulting from the presence of the valve and the higher fan speed, renders the heating apparatus less sensitive to pressure differences between the air inlet and the flue gas outlet, which pressure differences can for instance occur as a result of gusts of wind; in particular, greater counteracting pressures can be overcome;

3. Because the operating range wherein the burner does not resonate is increased, the gas/air mixture can freely be set at an optimum excess air, so that harmful emissions can be limited;

4. The heating apparatus can be started at low load without involving starting resonances (during the start, a conventional heating apparatus is typically extra sensitive to resonance, so that often, starting should take place above the low load);

5. During standstill of the apparatus, the valve, which is in the closed position, limits the standstill losses in that the through-flow of the heat exchanger with air under the influence of draft is drastically reduced

Claims

1. A valve to be fitted in a fuel/air-mixture duct, combustion air duct or flue duct of a heating apparatus with a modulating burner, wherein the valve (1) comprises a valve plate (3) arranged in the duct (2), which valve plate is pivotable between a closed position and an open position about a pivot (4) extending parallel to the valve plate (3) and positioned eccentrically relative to the center of the valve plate (3) so that on a first side of the pivot (4), the valve plate (3) extends by a larger valve plate subsurface (3a) and on the other side of the pivot (4), the valve plate (3) extends by a smaller valve plate subsurface (3b), characterized in that the valve (1) is an antiresonance valve comprising a closing spring (5) adapted to exert a closing moment on the valve plate (3), so that it is biased in a closed position, wherein the moment of mass inertia of the valve plate (3) is minimized, so that, in use, oscillations of the valve plate (3) are minimized, the spring (5) being constructed or arranged so that the closing moment decreases according as the valve plate (3) is pivoted further in the direction of the open position.

2. A valve according to claim 1, characterized in that the spring is a draw spring (5) of which a first free end (5a) engages the smaller valve plate subsurface (3b) and of which a second free end (5b) is attached to a fixed point (6) so that the moment arm of the force acting on the valve plate (3), i.e. the distance between the pivot (4) and an imaginary line in the direction of which the force acts, decreases according as the valve plate (3) is opened further.

3. A valve according to claim 1 or 2, characterized in that in the open position of the valve plate (3), the closing moment exerted by the spring (5) is virtually zero.

4. A valve according to claim 3, characterized in that the draw spring is a helical spring (5) which, in the open position of the valve plate (3), extends parallel to the valve plate surface, and of which helical spring (5) the center line, extending in the longitudinal direction of the spring (5), virtually intersects the center line of the pivot (4) in the open position of the valve plate (3).

5. A valve according to any one of the preceding claims, characterized in that it comprises a valve sleeve (7) having substantially the same diameter as the duct in which the valve (1) is to be fitted, wherein the pivot (4) is rotatably mounted in the valve sleeve (7).

6. A valve according to claims 2 and 5, characterized in that the valve sleeve (7) comprises a fastening hook (6) providing the fixed point for fastening the second end (5b) of the draw spring (5).

7. A valve according to any one of the preceding claims, characterized in that the valve (1) also comprises a stop (8) against which the valve plate (3) abuts in the closed position.

8. A heating apparatus, comprising a modulating premix burner (9) and a combustion air fan (10) whose outlet is connected, via a fuel/air-mixture duct (11) or a combustion air duct, to a combustion space (12) with an associated heat exchanger (13), wherein a flue duct (14) is connected to the combustion space (12) downstream of the heat exchanger (13), wherein the installation comprises a valve (1) according to any one of the claims 1 to 7.

9. A heating apparatus according to claim 8, characterized in that the valve (1) is arranged in the fuel/air-mixture duct (11).

Ansprüche

1. Ein in ein Brennstoff/Luft-Gemisch-Rohr, Verbrennungsluftrohr oder Rauchabzugsrohr einer Wärmevorrichtung mit einem Modulierbrenner einzusetzendes Ventil, wobei das Ventil (1) eine Ventilplatte (3) aufweist, welche in dem Rohr (2) angeordnet ist, wobei die Ventilplatte zwischen einer geschlossenen Position und einer geöffneten Position um einen Schwenkzapfen (4) schwenkbar ist, welcher sich parallel zur Ventilplatte (3) erstreckt und relativ zum Zentrum der Ventilplatte (3) exzentrisch plaziert ist, derart, daß sich auf einer ersten Seite des Schwenkzapfens (4) die Ventilplatte (3) durch eine größere Ventilplatten-Suboberfläche (3a) erstreckt und auf der anderen Seite des Schwenkzapfens (4) die Ventilplatte (3) durch eine kleinere Ventilplatten-Suboberfläche (3b) erstreckt, dadurch gekennzeichnet, daß das Ventil (1) ein Anti-Resonanzventil ist, welches eine Schließfeder (5) aufweist, welche angepaßt ist, ein Schließmoment auf die Ventilplatte (3) auszuüben, so daß sie in eine geschlossene Position ausgerichtet wird, wobei das Moment der Massenträgheit der Ventilplatte (3) minimiert ist, so daß in Benutzung Schwingungen der Ventilplatte (3) minimiert sind, wobei die Feder (5) aufgebaut oder angeordnet ist, so daß das Schließmoment abnimmt, in dem Maße wie die Ventilplatte (3) weiter in Richtung auf die offene Position geschwenkt wird.

2. Ventil nach Anspruch 1, dadurch gekennzeichnet, daß die Feder eine Zugfeder (5) ist, von der ein erstes freies Ende (5a) in die kleinere Ventilplatten-Suboberfläche (3b) eingreift und von der ein zweites freies Ende (5b) an einem festen Punkt (6) befestigt ist, derart, daß der Hebelarm der Kraft, welche auf die Ventilplatte (3) wirkt, d.h. der Abstand zwischen dem Schwenkzapfen (4) und einer imaginären Linie in der Richtung, in der die Kraft wirkt, abnimmt, in dem Maße wie die Ventilplatte (3) weiter geöffnet wird.

3. Ventil nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß in der offenen Position der Ventilplatte (3) das durch die Feder (5) ausgeübte Schließmoment nahezu Null ist.

4. Ventil nach Anspruch 3, dadurch gekennzeichnet, daß die Zugfeder eine Schraubenfeder (5) ist, welche in der offenen Position der Ventilplatte (3) sich parallel zur Ventilplatten-Oberfläche erstreckt, und wobei die Zentrallinie der Schraubenfeder (5), welche sich in der longitudinalen Richtung der Feder (5) erstreckt, nahezu die Zentrallinie des Schwenkzapfens (4) in der offenen Position der Ventilplatte (3) schneidet.

5. Ventil nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß es eine Ventilmanschette (7) aufweist, welche im wesentlichen denselben Durchmesser wie das Rohr hat, in welches das Ventil (1) einzusetzen ist, wobei der Schwenkzapfen (4) drehbar in der Ventilmanschette (7) angebracht ist.

6. Ventil nach Anspruch 2 und 5, dadurch gekennzeichnet, daß die Ventilmanschette (7) einen Befestigungshaken (6) aufweist, welcher den festen Punkt zum Befestigen des zweiten Endes (5b) der Zugfeder (5) vorsieht.

7. Ventil nach irgendeinem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Ventil (1) auch eine Sperre (8) aufweist, gegen welche die Ventilplatte (3) in der geschlossenen Position anstößt.

8. Heizvorrichtung, welche einen Modulations-Vormischbrenner (9) und einen Verbrennungsluft-Ventilator (10) aufweist, dessen Auslaß über ein Brennstoff/Luft-Gemisch-Rohr (11) oder ein Verbrennungsluftrohr mit einem Verbrennungsraum (12) verbunden ist, mit einem zugeordneten Wärmetauscher (13), wobei ein Rauchabzugrohr (14) mit dem Verbrennungsraum (12) stromabwärts des Wärmetauschers (13) verbunden ist, wobei die Anlage ein Ventil (1) nach irgendeinem der Ansprüche 1 bis 7 aufweist.

9. Heizvorrichtung nach Anspruch 8, dadurch gekennzeichnet, daß das Ventil (1) in dem Brennstoff/Luft-Gemisch-Rohr (11) angeordnet ist.

Revendications

1. Soupape devant être montée dans un conduit de mélange carburant/air, un conduit d'air de combustion ou un conduit de fumée d'un appareil de chauffage avec un brûleur de modulation, la soupape (1) comprenant une plaque de soupape (3) disposée dans le conduit (2), laquelle plaque de soupape peut pivoter entre une position fermée et une position ouverte autour d'un pivot (4) s'étendant parallèlement à la plaque de soupape (3) et positionné de manière excentrée par rapport au centre de la plaque de soupape (3) de telle sorte que, sur un premier côté du pivot (4), la plaque de soupape (3) s'étend avec une surface de plaque de soupape plus grande (3a) et de l'autre côté du pivot (4), la plaque de soupape (3) s'étend avec une surface de plaque de soupape plus petite (3b), caractérisée en ce que la soupape (1) est une soupape anti-raisonnance comportant un ressort de fermeture (5) prévu pour exercer un moment de fermeture sur la plaque de soupape (3), de sorte qu'elle est rappelée dans une position fermée, le moment d'inertie de masse de la plaque de soupape (3) étant minimisé, de sorte que, lors de l'utilisation, les oscillations de la plaque de soupape (3) sont minimisées, le ressort (5) étant construit et agencé de telle sorte que le moment de fermeture diminue en fonction du fait que la plaque de soupape (3) pivote davantage dans la direction de la position ouverte.

2. Soupape selon la revendication 1, caractérisée en ce que le ressort est un ressort de traction (5) dont une première extrémité libre (5a) engage la surface de plaque de soupape plus petite (3b) et dont une deuxième extrémité libre (5b) est fixée sur un point fixe (6) de sorte que le bras de moment de la force agissant sur la plaque de soupape (3), c'est-à-dire la distance entre le pivot (4) et une ligne imaginaire dans la direction de laquelle s'exerce la force, diminue en fonction du fait que la plaque de soupape (3) est davantage ouverte.

3. Soupape selon la revendication 1 ou 2, caractérisée en ce que, dans la position ouverte de la plaque de soupape (3), le moment de fermeture exercé par le ressort (5) est virtuellement nul.

4. Soupape selon la revendication 3, caractérisée en ce que le ressort de traction est un ressort hélicoïdal, qui, dans la position ouverte de la plaque de soupape (3), s'étend parallèlement à la surface de plaque de soupape, et l'axe du ressort hélicoïdal (5), qui s'étend dans la direction longitudinale du ressort (5), coupe virtuellement l'axe du pivot (4) dans la position ouverte de la plaque de soupape (3).

5. Soupape selon l'une quelconque des revendications précédentes, caractérisée en ce qu'elle comporte un manchon de soupape (7) ayant sensiblement le même diamètre que le conduit dans lequel doit être montée la soupape (1), le pivot (4) étant monté de façon rotative dans le manchon de soupape (7).

6. Soupape selon les revendications 2 et 5, caractérisée en ce que le manchon de soupape (7) comporte un crochet de fixation (6) procurant le point fixe pour la fixation de la deuxième extrémité (5b) du ressort de traction (5).

7. Soupape selon l'une quelconque des revendications précédentes, caractérisée en ce que la soupape (1) comporte également une butée (8) contre laquelle bute la plaque de soupape (3) dans la position fermée.

8. Appareil de chauffage, comportant un brûleur de modulation à prémélange (9) et un ventilateur d'air de combustion (10) dont la sortie est reliée, par l'intermédiaire d'un conduit de mélange carburant/air (11) ou d'un conduit d'air de combustion, à un espace de combustion (12) avec un échangeur de chaleur (13) associé, un conduit de fumée (14) étant relié à l'espace de combustion (12) en aval de l'échangeur de chaleur (13), l'installation comportant une soupape (1) selon l'une quelconque des revendications 1 à 7.

9. Appareil de chauffage selon la revendication 8, caractérisé en ce que la soupape (1) est disposée dans le conduit de mélange carburant/air (11).

Drawing