EP0888517A2

EP0888517A2 - Nozzle unit for oil burner

Info

Publication number: EP0888517A2
Application number: EP97914171A
Authority: EP
Inventors: Soren Bruun; Leif Bonnerup
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1996-03-19
Filing date: 1997-03-18
Publication date: 1999-01-07
Anticipated expiration: 2017-03-18
Also published as: EP0888517B1; DE69719491D1; AU2152397A; DE69719491T2; DK32196A; WO1997035148A1

Abstract

The invention concerns a nozzle unit for an oil burner consisting of a fan, a pump and a nozzle. The nozzle unit consists of a nozzle (2) and a pressure dependent valve (8). A cylinder (27) is arranged in the nozzle holder, in which cylinder the pressure dependent valve is mounted displaceably, so that the pressure dependent valve is pressed to rest against the nozzle by oil pressure.

Description

Nozzle unit for oil burner

The invention concerns a nozzle unit for an oil burner, where the oil burner consists of a fan, a pump and a nozzle, and where the nozzle unit consists of a nozzle and a pressure dependent valve.

DE 38 14 530 Cl describes an oil burner with a pressure dependent valve between oil preheater and nozzle. The purpose of the valve is to prevent dripping from the nozzle in the standstill periods of the burner.

DE 39 01 032 Cl describes a nozzle with a built-in pressure dependent valve. When the pump starts, the valve opens, but only when the pump has obtained sufficient pressure for a ball to compress a spring. Correspondingly, the spring presses the ball against the seat as soon as the pump speed reduces.

The pressure dependent valve is efficiently preventing dripping from the nozzle, both when the burner stops and heat radiation heats up the nozzle holder, and during start-up, while the oil preheater heats the oil. However, the valve must be replaced simultaneously with the nozzle, which is normally replaced once a year. The life of the pressure dependent valve is much longer, but it is scrapped together with the nozzle.

From DE 32 26 023 it is also known to place a valve between preheater and nozzle. Further, there is a bypass connection from the oil preheater to the low pressure side of the pump. The bypass connection also comprises a manually controllable flow restriction, enabling the setting of the amount of oil flowing through the bypass connection at a value at which the pump can maintain an optimum nozzle pressure.

Thus the problem with heating of oil in the preheater is solved in that the bypass connection diverts pressure when the pump is without pressure, and in the pressureless state the valve between preheater and nozzle is closed by a spring pressing the valve closing element against the valve seat. However, the valve is fixed in the nozzle holder, and cannot adapt to different nozzle lengths. In front of the valve a volume will be exposed to heat radiation when the burner stops, and the volume expansion can lead to oil dripping in the burning chamber. A large volume before the oil preheater leads to bad combustion at the start, as the oil is cold.

It is the purpose of the invention to describe a different placing of the pressure dependent valve, to enable the use of standard nozzles and to prevent unnecessary replacement of the pressure dependent valve, leaving the oil volume between valve and nozzle approximately unchanged.

This task can be solved in that a cylinder is arranged in a nozzle holder, in which cylinder the pressure dependent valve is mounted displaceably, by which the pressure dependent valve is pressed to rest against the nozzle by oil pressure.

This enables replacement of the nozzle without requiring simultaneous replacement of the pressure dependent valve.

At the same time, the pressure dependent valve will prevent leakage of oil at nozzle replacement. Also, the pressure dependent valve can be pressed against the nozzle by the oil pressure. Thus, the valve will automatically reduce the volume between nozzle and valve, independently of the total length of the nozzle. The pressure dependent valve could be a ball valve, in which the ball is pressed against a seat by a pressure spring, while the pump pressure acts in the opposite direction. This will result in a rigid valve, opening fast, when the pressure force on the ball exceeds the spring force.

The pressure dependent valve can be made with a valve seat co-operating with a closing member in the shape of a diaphragm, where the medium pressure influences the diaphragm in the opening direction, and a piston exerts pressure on the diaphragm against the valve seat by means of a resilient element. This will result in a valve, in which a predetermined opening pressure is required to open the valve, and the valve causes a minimum pressure drop when open. Thus, the nozzle mounted after the valve can utilise almost all the pressure supplied by a pump.

In the closed valve state, medium pressure can influence the diaphragm in the opening direction in a ringshaped chamber extending around the valve seat, where the diaphragm is influenced by medium with low pressure inside the valve seat in the closed valve state, whereas the whole diaphragm surface is influenced and presses against the piston in the open valve state. Thus, in the closed state, the medium pressure can influence a limited area, thus securing that the valve does not open until a predetermined pressure value is exceeded. When this pressure value is exceeded, and the valve opens, the nozzle will act as flow limitation, and the pressure increases. The increasing pressure influences the whole diaphragm surface, and the diaphragm presses the counter pressure piston back against stop. Thus the pressure drop across the valve decreases to a very low value. The valve can be made of a cylinder-shaped housing with radial channels connecting the outside of the cylinder with the ringshaped channel and the valve seat opening, by which the cylinder surface is provided with tracks connecting at least one radial channel with the medium inlet, and by which a hollow cylinder is fixed to the cylinder-shaped housing, which hollow cylinder contains a spring and a piston, and the diaphragm is fixed between the cylinder- shaped housing and the hollow cylinder. This causes that the valve can be made as one unit, which is easy to replace or clean during service, if faults should occur. Also, the tracks in the cylinder surface will form a filter stopping large particles, which might otherwise disturb the valve function.

The valve can be made of a cylinder-shaped housing with an external diameter permitting oil passage between valve housing and surrounding cylinder, where a ringshaped channel is arranged on the cylinder-shaped housing, said channel being connected with at least one radial channel, which is connected to the ringshaped chamber of the valve, by which the valve housing is sealed towards the surrounding cylinder by means of an O-ring arranged in a groove in the valve housing, and a hollow cylinder is fixed to the valve housing, said cylinder comprising a spring and a piston, and the diaphragm is fixed between the cylinder- shaped housing and the hollow cylinder. In this way it can be obtained that the passage between valve housing and surrounding cylinder acts as a filter retaining all large particles, so that the valve function is not influenced. As there is a ringshaped passage extending around the cylinder-shaped housing, an offset resting against the surrounding cylinder cannot act as a blocking, as this will cause an increased clearance on the opposite side. The pressure dependent valve can be mounted in a narrowing in a preheater, immediately after the heating elements. This gives a compact design in an existing preheater.

Advantageously, the pressure dependent valve can be mounted in a nozzle holder mounted in the normal oil preheater outlet. This will enable mounting of the pressure controlled valve in an existing oil preheater.

Advantageously, an oil filter can be arranged between the preheater and the pressure dependent valve. Thus the oil will be filtered, preventing foreign bodies and particles from reaching the valve.

The nozzle can be sealed towards the nozzle holder by means of a sealing ring fixed on the nozzle before mounting, by which the sealing ring seals against a breast in the nozzle holder. This moves the sealing to the front edge of the nozzle thread, and air in the thread between nozzle and nozzle holder will cause no trouble, and means for air relief will not be required. If, at the same time, the nozzle holder comprises the present breast for sealing, standard nozzles can be used, however without the sealing ring and the advantages it offers.

In stead, the nozzle sealing ring can seal against a sleeve on the nozzle, and the nozzle holder sealing surface can be inclined, by which the inclined surface presses the sealing ring radially towards the centre. This causes that one edge of the sealing ring is pressed firmly against the filter, so that the sealing ring is automatically removed at nozzle replacement.

In the following the invention is explained on the basis of drawings, showing: Fig. 1 A section through a first possible embodiment of the invention

Fig . 2 A section through a second possible embodiment

Fig . 3 A section through a third possible embodiment

Fig . 4 A section through a fourth possible embodiment

Fig . 5 An enlarged section of the displaceable cylinder from fig. 4 at closed valve

Fig. 6 Same section as fig. 5, however at open valve

Fig. 1 shows a nozzle unit 1 for an oil burner, comprising a nozzle 2 and an oil preheater 3. The oil preheater 3 is only shown schematically by a section line through a possible oil preheater, which is assumed to be commonly known. The oil preheater 3 is mounted in a housing 4, into which the nozzle 2 with its filter 5 is screwed by means of a thread 6. The nozzle 2 has a sealing surface 7 fixed against a plane surface on the housing 4 by means of the thread 6. This gives a sealing for the oil. Between oil preheater 3 and nozzle filter 5 there is a valve unit 8, consisting of a ball 9 co-operating with a seat 10. The ball 9 is influenced in the closing direction by a spring 11, controlled by a spring guide 12, by which the spring 11 will rest against a spring stop 13. The valve unit 8 is fixed in the housing 4 by a thread 14, and the sealing between housing 4 and valve unit 8 is made by an O-ring 15, sealing against a surface on housing 4. A pre-filter 16 is mounted before valve seat 10, and 17 is an O-ring sealing between the inner components of the oil preheater and the housing 4.

When starting a burner, a pump (not shown) will build up a pressure, and after a certain preheating time a solenoid valve in the oil pump will release pressure to the nozzle string. However, the ball valve 9 requires a high pressure before opening, as the active pressure area of the ball is very restricted. The valve opens suddenly, and the active pressure area increases suddenly, when a flow occurs around the ball. Thus oil under high pressure is suddenly released to the oil nozzle 2, in which atomising takes place by means of a swirl chamber. When the burner is turned off, the pressure supply is disconnected in that a solenoid valve in the pump is closed, and as soon as the pressure reduces, the spring 11 presses the ball 9 against the valve seat 10, and the valve closes.

Fig. 2 shows an alternative embodiment of the invention, in which the valve 8 is arranged in a nozzle holder 18 mounted in the outlet of the oil preheater 3. Here, the valve 8 is fixed in the nozzle holder in a thread 21, together with a pre-filter 19. The pressure dependent valve 8 seals against the nozzle holder 18 by means of an O-ring 22.

Sealing between nozzle 2 and nozzle holder 18 is here made by a clamping ring 23. The clamping ring is fixed around the nozzle filter 5 before mounting the nozzle. Before the thread is screwed home, there will be contact on surface 24 between the nozzle and the clamping ring 23 and on surface 25 between the clamping ring 23 and the nozzle holder. Clamping between the surfaces will prevent oil from reaching the thread 6. The sealing surface 7 of the nozzle 2 is now unused, and the drawing shows that there is a distance to the normal sealing surface of the nozzle holder. This causes that oil has no access to the thread 6, and air bubbles cannot arise in the thread, so means for air relief of this thread is not required.

Fig. 3 shows a section through a third alternative embodiment. Like fig. 1 and 2, fig. 3 shows a nozzle 2 and an oil preheater 3, between which a pressure dependent valve 8 is arranged, the design of which is described above. The invention in fig. 3 differs from fig. 1 in that the pressure dependent valve 8 is arranged in a cylinder

27, and the valve 8 itself is mounted in a piston-shaped unit 28, which is displaceable in the cylinder 27. The sealing between the piston-shaped unit 28 and cylinder 27 is made by an O-ring 34. The valve 8 is mounted in the piston unit 18, in which it is sealed by means of an O-ring

33. A flanged sleeve 31 fixes the valve 8 together with a pre-filter 30 and a socket 32 for fixing. Fig. 3 also shows the sealing ring 23 mentioned under fig. 2.

As the piston 28 is displaceable in the cylinder 27, the first pressurising of the system will cause the oil pressure to push the piston 28 to rest against the nozzle filter 5. This rest remains until the nozzle is replaced. If then a nozzle is mounted, which has a longer filter 5 than the previous nozzle, the whole piston unit 28 will be displaced backwards towards the oil preheater 3. If a nozzle with a shorter filter 5 is mounted, the oil pressure will displace the piston 28 forward to secure rest against the filter 5. Thus, there is always a minimum of oil between valve unit 8 and nozzle 2. The displaceable mounting of the piston 8 also facilitates replacement of the whole pressure valve unit during service, which may be preferred at certain, long intervals, as the pre-filter 30 also requires replacement.

Compared with fig. 3, fig. 4 shows an alternative embodiment, as here a diaphragm valve is used in stead of the previously shown ball valve. The fig. shows a nozzle holder 26, in which is mounted a nozzle 2 with a nozzle filter 5. The nozzle is fixed in a thread 6, and a ringshaped sealing element 23 is fixed against the nozzle by means of a sleeve 24 and with rest against the nozzle holder on a surface 25. This gives direct sealing against the nozzle filter 5, so that oil is prevented from reaching the thread 6. Thus an air pocket cannot occur in the thread, which is compressed under pressure, and which re- expands when the burner is stopped and oil is pressed out through the nozzle. The nozzle holder comprises a valve housing 35 arranged displaceably in the valve housing cylinder 27. The valve housing 35 is connected with a hollow cylinder 36, and between valve housing 35 and cylinder 36 a diaphragm 37 is fixed, which rests against a valve seat 38. A piston 39, pressed by a resilient element 40, presses the diaphragm 37 to rest against the valve seat 38. The diaphragm 37 is influenced in the opening direction by the medium pressure applied through a channel (not shown) along the outside of the cylinder 36. This channel is m connection with a radial channel 42, which again is in connection with a ring chamber 41, in which the medium pressure presses against the diaphragm. The valve seat 38 has a central opening which is connected with the nozzle filter 5 in its central area, and with the outside of the nozzle filter 5 through at least one radial channel 43. The assembling of the displaceable valve, comprising a valve housing 35 and a hollow cylinder 36 takes place by means of an edge 44 on the valve body 35, which is flanged around an edge on the hollow cylinder 36. Leakage along the cylinder-shaped valve housing is prevented by an O-ring 45 arranged m a ring in the cylinder-shaped housing.

Fig. 4a shows an enlarged section of fig. 4, in which an oil channel 45 is connected with a ringshaped channel 46, which again is connected with the radial channel 42. The channel 45 can be made as one or more tracks, either in the valve housing 35 or internally in the cylinder 27. An alternative solution could be to make the valve housing 35 with a smaller diameter than the cylinder 27. This would give an oil passage, which is independent of a possible offset placing of the valve housing 35. There will always be an open passage. Channel or passage 45 will act as an oil filter, as all large impurities in the oil will be stopped before having any influence on the valve function,

Fig. 5 and fig. 6 show an enlarged section of the valve housing 35 and 36. Fig. 5 shows the valve in the closed state, and in fig. 6 the valve is shown in the opened state. In the closed state in fig. 5 the diaphragm 37 is pressed against the valve seat 38 by the piston 39, which is again pressed by a spring 40 to rest against the valve seat 38. The opening pressure for the opening of the valve can only influence the ringshaped area of the channel 41. This means that a relatively high pressure is required for the diaphragm 37 to exert sufficient pressure against the piston 39 to compress the spring 40. When, however, the opening starts, i.e. a small oil flow runs from the radial track 42 to the ring channel 41 across the valve seat 38 to one of the two outlets, channel 43 or the direct way to the nozzle filter, the nozzle will act as a flow restriction, and the pressure behind the valve seat will start increasing. From fig. 6 it can be seen, how, in the open state of the valve, the whole diaphragm surface is exposed to medium pressure, as the flow restriction taking place over the valve seat 38 is very small compared with the opening are of the nozzle. This gives a valve with a very small pressure drop when the valve is open.

The invention can be used with a large number of different oil burners. A possible embodiment of an oil burner has separate pump and fan. Thus pre-ventilation of a burning chamber can take place when the pump is not rotating. Thus the solenoid valve in the pump or in front of the nozzle is not required. At pump standstill oil can be pressed back through the pump, and thus an oil preheater can be used without requiring any valves other than the one mentioned in the invention. Advantageously, the pump can also be used in oil heating plant with oil preheater, where a solenoid valve is available in the pump and where a bypass is provided for pressure release of the nozzle string.

Claims

Patent Claims

1. Nozzle unit for an oil burner where the oil burner consists of a fan, a pump and a nozzle, and where the nozzle unit consists of a nozzle and a pressure dependent valve, characterised in that a cylinder is arranged in a nozzle holder, in which cylinder the pressure dependent valve is mounted displaceably, by which the pressure dependent valve is pressed to rest against the nozzle by oil pressure.

2. Nozzle unit according to claim 1, characterised in that the pressure dependent valve is a ball valve, in which the ball is pressed against a seat by a pressure spring, while the pump pressure acts in the opposite direction.

3. Nozzle unit according to claim 1, characterised in that the pressure dependent valve is made with a valve seat co-operating with a closing member in the shape of a diaphragm, where the medium pressure influences the diaphragm in the opening direction, and a piston exerts pressure on the diaphragm against the valve seat by means of a resilient element.

4. Nozzle unit according to claim 4, characterised in that in the closed valve state, medium pressure influences the diaphragm in the opening direction in a ringshaped chamber extending around the valve seat, where the diaphragm is influenced by medium with low pressure inside the valve seat in the closed valve state, whereas the whole diaphragm surface is influenced and presses against the piston in the open valve state.

5. Nozzle unit according to claim 4 or 5, characterised in that the valve is made of a cylinder-shaped housing with radial channels connecting the outside of the cylinder with the ringshaped channel and the valve seat opening, by which the cylinder surface is provided with tracks connecting at least one radial channel with the medium inlet, and by which a hollow cylinder is fixed to the cylinder-shaped housing, which hollow cylinder contains a spring and a piston, and the diaphragm is fixed between the cylinder-shaped housing and the hollow cylinder.

6. Nozzle unit according to claim 4 or 5, characterised in that the valve is made of a cylinder-shaped housing with an external diameter permitting oil passage between valve housing and surrounding cylinder, where a ringshaped channel is arranged on the cylinder-shaped housing, said channel being connected with at least one radial channel, which is connected to the ringshaped chamber of the valve, by which the valve housing is sealed towards the surrounding cylinder by means of an O-ring arranged in a groove in the valve housing, and a hollow cylinder is fixed to the valve housing, said cylinder comprising a spring and a piston, and the diaphragm is fixed between the cylinder-shaped housing and the hollow cylinder.

7. Nozzle unit according to one of the claims 1 to 6, characterised in that the pressure dependent valve is mounted in a nozzle holder mounted in a normal oil preheater outlet.

8. Nozzle unit according to claim 7, characterised in that an oil filter is arranged between the preheater and the pressure dependent valve.

9. Nozzle unit according to one of the claims 1 to 8, characterised in that the nozzle is sealed towards the nozzle holder by means of a sealing ring fixed on the nozzle before mounting, by which the sealing ring seals against a breast in the nozzle holder.

10. Nozzle unit according to one of the claims 1 to 9, characterised in that the nozzle sealing ring seals against a sleeve on the nozzle, and the nozzle holder sealing surface is inclined, by which the inclined surface presses the sealing ring radially towards the centre.