GB2284473A

GB2284473A - Fan-assisted burner

Info

Publication number: GB2284473A
Application number: GB9422488A
Authority: GB
Inventors: Reinhold Kehl
Original assignee: Joh Vaillant GmbH and Co
Current assignee: Vaillant GmbH
Priority date: 1993-11-08
Filing date: 1994-11-08
Publication date: 1995-06-07
Anticipated expiration: 2014-11-08
Also published as: DE4439741C2; NL9401854A; DE4439741A1; GB2284473B; ATA225393A; AT400356B; GB9422488D0

Description

2284473 Fan-assisted burner The present invention relates to a

fan-assisted burner comprising a fan, which is disposed in a vacuum chamber, and a mixture-forming tube provided with a gas inlet and an air inlet and protruding into a tubular suction port of the fan, in which a first measuring passage, to which the mixture pressure PK is applied, a second measuring passage, to which the pressure p, in the vacuum chamber is applied, and the gas inlet extend through a connector bracket, which defines the vacuum chamber, and the said passages open into a flange surface of the connector bracket, which flange surface is substantially planar and serves for connection to a gas control fitting.

is A fan-assisted burner having that design has been disclosed in German Utility Model G 91 12 281.3. A connector bracket is provided, which establishes a mechanical connection between the f an space and the gas control f itting and provides the measuring passages and the gas supply line. The measuring passages transmit the pressure conditions in the vacuum chamber p, and the mixture chamber PK to corresponding control means of the gas control fitting. The pressures p, and PK ref lect also the influences of different geographic or meteorological conditions on the air pressure. For that purpose the two pressures PL and PK are applied to diaphragm chambers of a differential pressure sensor, which generally comprises a continuous pressure cell. The resultingdifferential pressure signal may be a mechanical or electrical signal and is delivered virtually as a correcting quantity to the gas pressure regulator of the gas control fitting. Such an arrangement has been disclosed in Published German Application 39 11 268. In that connection a problem and disadvantage resides particularly in the long path for transmitting the pressures PL and p,,- Because the space is confined and the pressure cell is remote the measuring passages must consist of flexible capillaries. This results in risks particularly as regards the reliability in operation and the tightness.

It is an aim of the present invention to obviate the disadvantages and to simplify a fan-assisted burner of the construction set out in the opening paragraph of the present specification as regards its means for transmitting the measuring pressure.

Accordingly, in a burner according to the present invention, the flange surface has recess-forming groovelike portions, which connect the first and second measuring passages to ports, which are disposed laterally of the flange surface and serve for connection to a pressure cell, which serves to generate a continuous differential pressure signal /PK - PL/ and is closely adjacent to a lateral surface of the connector bracket, which lateral surface is substantially at right angles to the flange surface, and in which the differential pressure signal /p, - pJ is delivered to control means of the gas control fitting.

Such a burner may thus have short measuring passages, which branch off virtually within the f lange surface of the bracket. The pressure cell can be arranged on a lateral surf ace of the bracket without a problem particularly if a pressure cell of the latest construction is used, which is distinguished by a small space requirement and by the generation of an electrical differential pressure signal. Because the pressure cell is directly mounted on a lateral surface of the connector bracket there is no need for connecting flexible tubes or connecting capillaries.

The features of claim 2 permit a simple mounting of the pressure cell on the connector bracket. The spring is claw joint permits the pressure cell to be clipped in for a convenient assembling. A demounting which may be necessary is just as simple. There is no need for a disconnecting of connecting elements, such as screws and the like.

The geometric design of the connector bracket according to claim 3 permits the same to be manufactured without a problem. The planar mounting surf aces permit the use of f lat sealing disks. Specifically, the connector bracket can reliably be sealed from the gas control fitting in that a single gasket, which has a plurality of apertures, is interposed.

The connector bracket is preferably designed in accordance with claim 4 as a compact aluminium diecasting.

All shaped portions, e.g., also the recess-forming groove like portions of the flange surface, are thus moulded by the diecasting mould.

Relevant parts of an example of a burner made in accordance with the present invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a diagram of a connector bracket and serves to illustrate the functional relationships to parts connected thereto; Figure 2 is a top plan view showing a flange surface of the connector bracket shown in Figure 1; Figure 3 is a sectional view of the bracket taken on the line III-III shown in Figure 2; Figure 4 is an elevational view of the bracket as viewed in the direction of the arrow IV shown in Figure 2; and Figure 5 is an elevational view of the bracket, partly in section, as viewed in the direction of the arrow V shown in Figure 2.

Figure 1 illustrates the relative spatial arran gement of a vacuum chamber 1, a connector bracket 2 and a gas control fitting 3. The vacuum chamber 1 contains a fan, not shown. The connector bracket 2 has a flange sur face 4, which registers with a mating surface 6 of the gas control fitting 3 with a large-surface gasket 5 interposed between the flange surface 4 and the mating surface 6. The connector bracket 2 has a surface 7, which is at right angles to the flange surface 4 and shields the connector bracket 2 from the vacuum chamber 1. The passages extending through the connector bracket 2 substantially comprise three angle bores, which open at one end in the flange surface 4 and at the other end in the surface 7. A first angle bore is constituted by a gas pipe 8. The two other angle bores define measuring passages 9 and 10. A first measuring passage 9 serves to transmit a mixture pressure p, which prevails within a mixture-forming tube 11. The mixture-forming tube 11 is provided with a gas inlet 12 and an air inlet 13. The gas inlet 12 is a separate tubular piece, which protrudes into and is sealed to the gas pipe 8 of the connector bracket 2. A capillary 14 or a further tubular piece, which concentrically surrounds the gas inlet 12, transmits the mixture pressure PK first from the mixture-forming tube 11 to the connector bracket 2. Inside the connector bracket 2 the mixture pressure pK is transmitted by the angled first measuring passage 9 as far as to the flange surface 4.

The connector bracket 2 contains a gas inlet pipe 15, through which the gas is supplied to the gas control fitting 3, by which the gas flow is adapted to the actual demand by two solenoid gas valves 16 and 161 and a gas pressure regulator 17. The gas which has been released then f lows through the angled gas pipe 8 into the gas inlet 12.

It is emphasized that the foregoing description of the region containing the f an and of the gas control fitting 3 is mainly directed to the function and arrangement of the connecting passages 9, 10, 12 and 15.

Specifically, means for controlling the supply of air adjacent to the fan and a gas pressure -responsive switch and other parts of the gas control fitting 3 have not been described because they are not part of the subject matter of the present invention.

The modification of the flange plate 4 is shown in greater detail in Figure 2. It is apparent that the measuring passages 9 and 10 open into cavities 18 and 19, which are enlarged in box shape. Said cavities 18 and 19 communicate through corresponding apertures in the gasket is 5 with continuing lines in the gas control fitting 3, as is schematically shown in Figure 1. Further recess-forming groovelike portions 20 and 21 branch from the cavities 18 and 19, which are emphasized by crosses and dots, respectively. Said groovelike portions 20 and 21 serve to transmit the measuring pressures p. and PL to ports 22 and 23, which are disposed laterally of the flange surface 4 and serve for connection to a pressure cell 24. Those passage portions which directly communicate with the ports 22 and 23 consist of angle bores 25 and 26, which extend from the groovelike portions 20 and 21. The angle bore 26 for transmitting the negative pressure PL and the region adjacent to the port for connection to the pressure box 24 are shown in detail in Figure 5. The pressure cell 24 essentially comprises two diaphragm chambers, to which the pressure PK of the measuring passage line 14 - 9 - 18 - 20 - 25 and the pressure p, of the measuring passage line 10 19 - 21 - 26 are applied. The diaphragm transmits the pres sure difference /PK - PL/ to an electronic transducer, which generates an electric output signal, which can be taken from the terminal 27 of the pressure cell 24. The pressure cell 24 is directly mounted on the bracket 2 on a lateral surface 28 of the latter, which is at right angles to the flange surface 4. In addition to the tubular ports 22 and 23, the means for making that connection comprise a spring claw joint 29 and a rigid hook joint 30, which is partly visible in Figure 3. The passage lines and the arrangement is of the pressure cell 24 permit the pressures PK and PL to be transmitted over the shortest possible paths and eliminate the need for flexible pressure tubes and connecting elements which can be sealed only with difficulty. The parts which are not incorporated in the highly compact diecast connector bracket 2 comprise only the pressure cell 24 and a gas nozzle, which is inserted in the gas pipe 8.

The diecasting mould moulds also the stiffening ribs 32a, 32b and connecting bores, one of which is designated 33 by way of example.

Figure 3 shows the angled shape of the second measuring passage for forwarding the negative pressure p,, and for the forwarding of that pressure over the groovelike portion 21. 32c is a further stiffening rib, which extends substantially in the plane of the axis of the second measuring passage 10, as is apparent from Figure 5. Parts 8, 19, 26 and 31 are provided with dash lead lines because only the outer contours are actually visible in the view of Figure 3. The direction of view can be compared to that of Figure 1.

Figure 4 is a top plan view on the surf ace 7, which is adjacent to the vacuum chamber 1 and is at right angles to the flange surface 4 and at right angles to the lateral surface 28. The mouths of the angle bores for the gas pipe 8, the first measuring passage 9 for the mixture pressure PK and the second measuring passage 10 for the negative pressure p,, are apparent. That leg of the first is measuring passage 9 which is apparent from Figure 4 comprises an annular passage, which concentrically surrounds the gas pipe 8. The second leg of the angle branches as a radial bore from that annular passage.

Figure 5 shows in elevation the connector bracket 2 viewed in a direction which is opposite to the direction of view in Figure 4. The view is virtually directed to the rear side of the surface 7. That region which is shown in section contains the portion in which the angle bore 25 is connected, which extends from the groovelike portion 20, i.e., from the cavity 18 which is formed in the flange surface 4 and communicates with the first measuring passage 9. It is apparent that the pressure cell 24 comprises a conical port 34, which is fitted in a tubular seal 35 in the angle bore 25. A further stiffening rib 32d, which is associated with the tubular gas inlet 15, is also visible. 5 The invention is not restricted to the embodiment which has been described hereinbefore by way of example. Various modifications may be contemplated, in which the features of the invention may be embodied even if the design is basically different.

Claims

1. A fan-assisted burner comprising a fan, which is disposed in a vacuum chamber, and a mixture-forming tube provided with a gas inlet and an air inlet and protruding into a tubular suction port of the fan, in which a first measuring passage, to which the mixture pressure PK 'S applied, a second measuring passage, to which the pressure PL in the vacuum chamber is applied, and the gas inlet extend through a connector bracket, which defines the vacuum chamber, and the said passages open into a flange surface of the connector bracket, which flange surface is substantially planar and serves for connection to a gas control fitting, in which the flange surface has is recess-forming groovelike portions, which connect the first and second measuring passages to ports, which are disposed laterally of the flange surface and serve for connection to a pressure cell, which serves to generate a continuous differential pressure signal /PK - PL/ and is closely adjacent to a lateral surface of the connector bracket, which lateral surface is substantially at right angles to the flange surface, and in which the differential pressure signal /PK - pJ is delivered to control means of the gas control fitting.

2. A fan-assisted burner according to claim 1, in which the pressure cell is connected to the connector bracket by the two ports and at least one spring claw joint.

3. A fan-assisted burner according to claim 1 or claim 2, in which the connector bracket comprises substantially three substantially planar mounting surfaces, which are substantially at right angles to each other and are constituted by the f lange surf ace f or connection to the gas control fitting, the surface which defines the vacuum chamber and the lateral surface for connection to the pressure cell.

4. A fan-assisted burner according to any preceding claim, in which the connector bracket comprises an aluminium diecasting.

5. A fan-assisted gas burner substantially as described herein with reference to and as illustrated in the drawings.