EP2908055B1 - Gas valve with integrated air pressure monitor - Google Patents

Description

The invention relates to a gas valve for use in connection with a gas burner, which has a valve seat and a valve body, the opening position of which is controlled exclusively pneumatically by a vacuum of a combustion air acting on the gas valve. A first pneumatic pressure regulator is provided in the gas valve, which is in pneumatic operative connection with the valve body at a first control pressure and serves to regulate the composition of a gas-air mixture supplied to the burner.

Such regulation of the composition of the gas-air mixture supplied to the burner is influenced as a function of a suction pressure of the combustion air (underpressure), the outlet pressure of the gas. This is done by opening or closing the gas valve depending on the suction pressure. It is known from the prior art to use so-called servo pressure regulators, in which the opening position of the valve body is determined by the pneumatic forces acting on the gas valve. The closing force of the valve body is determined by a spring. The opening force is determined via a pressure (gas pressure and suction pressure) acting on a membrane which is connected to the valve body. It is also known to set the servo pressure regulator with a negative control pressure of approx. -20 to +20 Pa as a zero point shift (offset), so that the gas-air ratio can be precisely regulated and an optimal air ratio characteristic can be generated during combustion.

However, it is problematic here that the set offset value changes over the life of the gas valve and that a safety shutdown in the event of an exhaust pipe blockage, a condensate jam or a supply air pipe blockage no longer works reliably. In the prior art it is provided as monitoring means that a differential pressure measurement is provided on the orifice or on the venturi of the blower interacting with the gas valve, which detects changes via an air pressure monitor and with a corresponding drop in the output, the pressure difference and the ionization current and an increase the air ratio of the air pressure switch or the ionization monitoring of the burner control unit switches off the gas supply. The change in the offset value on the pressure regulator means that a lean air / gas mixture would have to be set as the initial value for the new device, which, however, leads to combustion noises at low load values and can lead to unsanitary burns.

The state of the art in print is from the document US 6,263,908 B1 known in which a slowly opening gas valve is disclosed, but which will not operate exclusively pneumatically.

Against this background, it is an object of the invention to provide a gas valve which automatically changes to a closed position as soon as the negative suction pressure of the combustion air drops unnaturally (pressure increase).

The invention is achieved by the combination of features according to patent claim 1.

The gas valve according to the invention is usually connected to a venturi nozzle which, in cooperation with a fan, delivers combustion air to a burner, the narrowest cross section of the venturi nozzle being known to generate the maximum negative pressure and acting as suction pressure at the outlet of the gas valve. The combustion gas is then mixed into the combustion air in the Venturi nozzle. Depending on the blower and the type of construction, vacuum levels of, for example, -50 (partial load) to -1,250 Pa (full load) are reached as suction pressure. This suction pressure acts on the gas valve and, together with the positive gas inlet pressure, determines the opening position of the valve body.

If the exhaust pipe is blocked, the suction pressure increases (negative pressure drops). The solution of the gas valve according to the invention uses this pressure increase by providing a second pneumatic pressure regulator, which is also in pneumatic operative connection with the valve body, but the control pressure of the second pressure regulator is significantly lower than that of the prior art and for adjusting the air ratio used the first pressure regulator. The control pressure (offset) of the second pressure regulator is set or fixed in such a way that its valve opens when the suction pressure rises and thus opens to the Diaphragm of the valve body acting pressure collapses, whereby the valve body is brought into the closed position via the associated spring. The second pressure regulator of the gas valve thus only serves as an air pressure switch.

In a favorable embodiment it is provided that the first and second control pressures can each be preset by a membrane-spring combination of the first and second pressure regulators. The membrane-spring combination enables only pneumatic control via the suction pressure of the combustion air and the gas pressure, whereby the control pressure (offset) can be set by a specific choice of spring and its preload. The first pressure regulator for setting the optimal air characteristic curve has a second spring, by means of which the corresponding offset value can be variably adjusted.

According to the invention, in a favorable embodiment, it is also provided that the second pressure regulator is also equipped with a corresponding second spring, so that the offset value can also be variably set here. In a more cost-effective and simplified embodiment, however, it can also be provided that the second pressure regulator is assigned a fixed control pressure value (offset value) which is not variable but less than the first control pressure. Then there is no need for a second spring.

In normal operation, the valve of the second pressure regulator is held in a closed position by the negative pressure of the combustion air acting on the gas valve, but opens when the negative pressure (suction pressure) drops below a predetermined value. In one embodiment of the invention it is provided that the gas valve has a channel which pneumatically connects a region of the maximum negative pressure of the combustion air to the second pressure regulator. As the area of maximum Vacuum of the combustion air usually uses the range of the maximum suction pressure, ie the range of the gas valve which is connected to the venturi.

The gas valve also has a main quantity throttle or a main orifice for controlling the amount of gas to be released or supplied to the combustion air, the pressure, as seen in the direction of flow of the gas, being different in front of (p2) or behind (p1) of the main quantity orifice or main orifice. The maximum negative pressure (suction pressure p1) of the combustion air acts in the flow direction after the main quantity throttle. Seen in the flow direction in front of the main flow restrictor, in addition to the suction pressure of the combustion air, the gas pressure provided by the gas line, which is provided as an excess pressure of approx. 20 mbar from the gas line, acts. Therefore, the pressure (p2) in the flow direction is higher upstream of the main flow restrictor or the main orifice (lower negative values). According to the invention, it is provided that the second pressure regulator is pneumatically connected to the area downstream of the main quantity throttle or the main orifice, as seen in the gas flow direction. For example, this can be done via the channel described above. This ensures that the suction pressure of the combustion air acts directly on the second pressure regulator and that a drop in the vacuum due to, for example, an exhaust pipe blockage acts directly on the second pressure regulator and leads to its valve opening, causing the valve body of the gas valve to move into a closed position.

In a favorable embodiment, it is also provided that both the first and the second pressure regulator are designed as modules and the modules are accommodated together in a gas valve housing. This can be guaranteed in a kind of modular principle, different components in summarize a housing. The costs are reduced.

The first and second pressure regulators are preferably designed as servo pressure regulators and each have an upper and lower pressure chamber separated by a membrane, it being known from the prior art to connect the upper pressure chamber of the first pressure regulator to a fixed reference pressure. According to the invention, it is provided in an advantageous embodiment to connect the upper pressure chambers of the first and second pressure regulators to one another in order to connect the two upper pressure chambers together with a fixed reference pressure.

In an advantageous further embodiment of the invention it is provided that the valve body is formed with an elastomer, so that the gas valve serves as a tight safety valve. This can ensure that a gas leakage value of the gas valve remains below a predetermined maximum value, for example below 40 milliliters per hour. It is particularly advantageous here that the main gas safety valve, which is always to be provided for safety reasons in addition to the valve controlling the gas quantity, only has to be designed as a simple safety valve, which is considerably cheaper than double-formed safety valves.

Fig. 1

eine Schnittansicht eines Gasventils mit doppeltem Sicherheitsventil gemäß dem Stand der Technik;

Fig. 2

das erfindungsgemäße Gasventil in einer ersten Ausführungsform;

Fig. 3

das Gasventil aus Fig. 2 in einer vergrößerten Ansicht;

Fig. 4

eine weitere Ausführung des erfindungsgemäßen Gasventils;

Fig. 5

eine weitere Ausführung des erfindungsgemäßen Gasventils als Sicherheitsventil, und

Fig. 6

das erfindungsgemäße Gasventil in einer Ausführungsform mit einfach wirkendem Sicherheitsventil.

Other advantageous developments of the invention are characterized in the subclaims or are shown below together with the description of the preferred embodiment of the invention with reference to the figures. Show it:

Fig. 1

a sectional view of a gas valve with double safety valve according to the prior art;

Fig. 2

the gas valve according to the invention in a first embodiment;

Fig. 3

the gas valve Fig. 2 in an enlarged view;

Fig. 4

a further embodiment of the gas valve according to the invention;

Fig. 5

a further embodiment of the gas valve according to the invention as a safety valve, and

Fig. 6

the gas valve according to the invention in an embodiment with a single-acting safety valve.

The figures are schematic by way of example, the same reference symbols denoting the same components in all the design variants.

Fig. 1 shows the combination of a gas valve 100 integrated in a gas valve housing 118, which has a valve body 103, the opening position of which determines a gas flow quantity. The quantity of gas can be adjusted via a main quantity throttle 117. A double-acting safety valve 101 is installed upstream to protect against gas leakage. A pressure regulator 4 is provided for setting the air ratio characteristic curve, the control pressure (offset pressure) of which can be set to a value from -20 to +20 Pa. The means for monitoring a possible pressure drop, which are usually provided in the prior art by an air pressure monitor on the main quantity throttle or the venturi, are not shown.

In Fig. 2 A solution according to the invention of an exemplary embodiment of the gas valve 1 is shown in a sectional view, the gas valve 1 having a valve seat 2 formed on a gas valve housing 18 and a valve body 3, the opening position of which pneumatically via a negative pressure of the combustion air (suction pressure p1), which is at most in the range 16 acts on the gas valve 1, and has a first pneumatic pressure regulator 4 and a second pneumatic pressure regulator 5, which are each in pneumatic operative connection with the valve body 3 with a first or second control pressure. The second control pressure of the second pressure regulator 5 is set to a lower value than the first pressure regulator 4, so that there is an action on the valve body 3 which is shown in FIG Fig. 3 is shown in more detail.

The detailed view from Fig. 3 shows that the gas valve is off Fig. 2 , with the gas valve housing being omitted for reasons of clarity. The valve body 3 is in a closed position and rests on the valve seat 2. The gas acts via the pressure provided by the supply line and flows through the gas valve in the direction of arrow G as well as in Fig. 2 shown. At the same time, the gas pressure acts through the valve body 3 on a membrane 12 which divides the membrane space 13 into an upper membrane space 14 and a lower membrane space 15. The gas pressure acting on the membrane 12 in the upper membrane space 16 counteracts the spring force of the spring 12 ′ which pushes the valve body 3 into a closed position. At the same time, the negative suction pressure of the combustion air p2 acts on the membrane 12 and pulls the valve body 3 into an open position. The first pressure regulator 4 has a valve 10 ', which has a predetermined opening position via a membrane-spring combination 6. In normal operation, the first pressure regulator 4 is set a first offset control pressure, which is used exclusively for the optimal setting of the air ratio. A flow connection is provided via the feedback channel 35, with which the set control pressure can be checked. The control pressure can be varied via an additional spring 8. An upper pressure chamber 21 and a lower pressure chamber 23 are determined by a membrane 19. The upper pressure chamber 21 is connected to ambient pressure or a predetermined reference pressure. The Connection can be ensured via a connector 45 to which a corresponding hose can be connected. The structure of the second pressure regulator 5 is identical to that of the first pressure regulator 4, the second control pressure (offset pressure) being lower than that of the first pressure regulator 4. A typical value of the second control pressure is, for example, -30 Pa. The second control pressure is set via the membrane-spring combination 7 and is variably adjustable via an additional second spring 9. A membrane 20 separates an upper pressure chamber 22 from a lower pressure camera 24. In normal operation, valve 10 is always closed due to the lower control pressure. In normal operation, the suction pressure p1 acts directly on the membrane 20 via the channel 15 and keeps the valve 10 closed. When the suction pressure p1 increases due to, for example, an exhaust pipe blockage, the negative pressure acting on the membrane 20 is reduced, so that the valve 10 opens. The pressure of the gas acting in the upper membrane chamber 14 collapses due to the abruptly increasing outflow through the channel 15, so that the spring 12 ′ presses the valve body 3 against the valve seat 2. The connection of the second pressure regulator 5 and its lower pressure chamber 24 directly to the suction pressure p1 via the channel 15 enables the gas valve 1 to be closed quickly and immediately, so that the second pressure regulator functions as an air pressure monitor for the suction pressure. As soon as the gas valve 1 is closed, a flame flow probe is used to determine that the necessary gas supply is missing and that the burner is switched off via an automatic burner control system.

In Fig. 4 is an alternative version to Fig. 3 shown, with all features being identical, except that the second pressure regulator 5 is designed without an additional second spring 9. The second pressure regulator 5 is set once via the diaphragm-spring combination 7 to a predetermined one Value (for example -30 Pa) that cannot be changed during operation. Otherwise, the function is identical to that of gas valve 1 Fig. 3 .

In Fig. 5 Another embodiment is shown, with all the features of those of the Fig. 3 correspond. In modification of the embodiment Fig. 3 the valve body 3 has an elastomer 25 which cooperates with the valve seat 2 in a closed position of the valve. The gas valve 1 thus becomes a safety valve with limited gas leakage and enables a single-acting safety valve to be replaced instead of a double-acting safety valve 30 Fig. 2 . Such an overall construction of the gas valve 1 Figure 5 with simple safety valve 30 'is in Figure 6 shown.

The embodiment of the invention is not limited to the preferred exemplary embodiments specified above. Rather, a number of variants are conceivable which make use of the solution shown even in the case of fundamentally different types. For example, instead of a modular design of the pressure regulator, a juxtaposition of conventional regulators can also be used.

Claims (12)

1. A gas valve (1) for interacting with a blower, which conveys combustion air to a burner, comprising:

   a valve seat (2) and a valve body (3), the opening position of which is exclusively pneumatically controlled by a partial vacuum of the combustion air acting on an outlet of the gas valve (1),

   a first pneumatic pressure regulator (4), which has a pneumatic operational connection to the valve body (3) using a first control pressure, and

   a second pneumatic pressure regulator (5), which has a pneumatic operational connection to the valve body (3) using a second control pressure, wherein

   the second control pressure is less than the first control pressure.
2. The gas valve as claimed in claim 1, characterized in that the first and second control pressure are each pre-settable by a membrane-spring combination (6, 7) of the first and second pressure regulator (4, 5).
3. The gas valve as claimed in any of the preceding claims, characterized in that the first and second control pressure are each variably settable by a membrane-spring combination (6, 7) in conjunction with a respective additional spring (8, 9) on the first and second pressure regulator (4, 5).
4. The gas valve as claimed in at least one of the preceding claims, characterized in that the first and second pressure regulator (4, 5) are each pneumatic servo valves.
5. The gas valve as claimed in at least one of the preceding claims, characterized in that the second pressure regulator (5) comprises a valve (10), which in normal operation is held in a closed position by the partial vacuum of the combustion air acting on the gas valve (1) and opens in the event of a drop of the partial vacuum below a predetermined value.
6. The gas valve as claimed in any of the preceding claims, characterized in that the open position of the valve body (3) is controllable via a membrane-spring combination (11) acting on the valve body (3) and the membrane (12) divides a membrane chamber (13) into an upper and a lower membrane chamber (14, 15), wherein the upper membrane chamber (14) is directly pneumatically operationally connected to the first and second pressure regulator (4, 5).
7. The gas valve as claimed in preceding claims 5 and 6, characterized in that an open position of the valve (10) of the second pressure regulator (5) establishes a pneumatic connection between the upper membrane chamber (14) and the combustion air acting with partial vacuum on the gas valve (1), which results in closing of the valve body (3).
8. The gas valve as claimed in at least one of preceding claims 1 to 7, characterized in that it comprises a duct (15), which pneumatically connects a region (16) of the maximum partial vacuum of the combustion air to the second pressure regulator (5).
9. The gas valve as claimed in at least one of preceding claims 1 to 7, characterized in that it comprises a main quantity throttle (17) or main aperture for controlling the gas quantity and a duct (15), which pneumatically connects a region downstream of the main quantity throttle (17) or main aperture to the second pressure regulator (5) viewed in the gas flow direction.
10. The gas valve as claimed in at least one of the preceding claims, characterized in that the first and second pressure regulators (4, 5) are formed as modules and are accommodated together in a gas valve housing (18).
11. The gas valve as claimed in at least one of the preceding claims, characterized in that the first and second pressure regulator (4, 5) each comprise an upper and lower pressure chamber (21, 22, 23, 24) separated by a membrane (19, 20) and the upper pressure chambers (21, 22) are connected.
12. The gas valve as claimed in at least one of the preceding claims, characterized in that the valve body is formed using an elastomer (25) and thus the gas valve (1) is formed as a safety valve.

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