The invention relates to an oil-fired apparatus and is particularly concerned with an improvement in a burner known as shell-type burner made by us so that the burner will be capable of burning diesel oil.

The existing shell-type burner produced by us comprises a well which receives oil from the supply, a wick extending around the well and via which the oil is burned and an upwardly extending cylindrical shell around the wick and which is formed with a multiplicity of perforations to permit passage of air therethrough. Hitherto, two concentric wicks have been provided each of which is positioned between two concentric upwardly extending perforated shells. Whilst such a shell-type burner works perfectly well with conventional heating oil, diesel oil does not burn particularly well in the burner and an object of the present invention is to provide an improved apparatus which will enable diesel oil to be burned. The apparatus will then be particularly useful in markets where diesel oil is widely used.

According to a first aspect of the present invention there is provided an oil-fired apparatus comprising a

well which receives oil from a supply, a wick in fluid communication with the well and via which the oil is burned, an upwardly extending shell adjacent the wick and which is formed with a multiplicity of perforations to permit passage of air therethrough and a shroud adjacent the perforated shell to reduce heat loss from the apparatus, the shroud being spaced from the shell so as to define an air passageway leading to the perforations in the shell.

By providing the shroud, the apparatus operates at a higher temperature than our prior burner and improves flow of air through the perforations in the shell thereby enabling diesel oil to be burned readily.

According to a second aspect of the present invention there is provided an oil-fired apparatus comprising a well which receives oil from a supply, a wick extending around the well and via which the oil is burned, an upwardly extending shell adjacent the wick and which is formed with a multiplicity of perforations to permit passage of air therethrough, and a shroud adjacent the perforated shell to reduce heat loss from the apparatus, the shroud being spaced from the shell so as to define an air passageway leading to the perforations in the shell. Preferably, two upwardly extending perforated shells are provided with the wick therebetween.

In one embodiment, at least two wicks are provided each of which is preferably positioned between two upwardly extending perforated shells. In another embodiment a single wick is provided and is preferably positioned between two upwardly extending perforated shells.

Preferably, the wicks and the associated shells are concentric.

The shroud is preferably concentric with its adjacent perforated shell and is preferably arranged around the outermost perforated shell.

The shroud may be supported by the shell or by a plurality of the shells.

An air inlet to the air passageway is preferably defined between the lower end of the shroud and an adjacent part of the apparatus.

For maximum heat retention we prefer the shroud to be unperforated.

In one embodiment a second shroud is positioned within the innermost shell.

According to a third aspect of the invention there is provided an oil-fired apparatus comprising a well

which receives oil from a supply, a wick in fluid communication with the well and via which oil is burned, two upwardly extending shells with the wick therebetween, each shell being formed with a multiplicity of perforations, an outer shroud around the outer shell and an inner shroud within the inner shell, each shroud being spaced from its associated shell so as to define an air passageway leading to the perforations in the associated shell.

Closure means may be provided for inhibiting the escape of air between the upper end of the perforated shell or one of the perforated shells and the adjacent shroud. The closure means may comprise a member which has the shroud extending therefrom.

Where each wick is positioned between two perforated shells, each pair of shells may define an opening between upper ends of the shells and closure means may be provided between a shell associated with one wick and an adjacent shell associated with the other wick to prevent the escape of air through the opening.

Where perforated shells are provided, further closure means may be provided so as to close the upper end of the innermost perforated shell to prevent air escaping therethrough.

The shell or shells may be supported by a base member which is formed with air inlet means for admitting air through the perforations.

The aforesaid well is preferably formed in the base member. In one embodiment the well is positioned substantially centrally of the base and the base member may define passageways through which oil can flow from the well to the or each wick. In another embodiment, the well may be arranged at an off-centre position and may have an opening at its upper end for receiving part of a said wick whereby that part will be in direct contact with oil in the well when the apparatus is in use.

Oil-fired apparatuses in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which:

Fig. 1 is a vertical cross-section through one form of the apparatus in the form of a burner in accordance with the invention on the line X-X in Fig.

2;

Fig. 2 is a broken away plan view of part of the burner of Fig. 1;

Fig. 3 is a vertical cross-section through another form of the apparatus in the form of another burner, in accordance with the invention on the line Y-Y in

Fig. 4 and

Fig. 4 is a plan view of the burner of Fig. 3.

In Figs 1 and 2 an annular base member 10 is made from a material such as cast iron and is formed with a central well 12 having an inlet port 11 for diesel oil. The base member 10 is formed with a plurality of concentric cylindrical walls 13,14,15, 16 which extend upwardly. A further upwardly extending wall 17 is provided adjacent the well 12 and supports a removable cover 18 above the well. Three radial members 19 extend between the walls 13 and 17 and three similar radial members 20 extend between the walls 14 and 15. The members 19 and 20 are formed with radial passageways 19a and 20a respectively, the passageways 19a, 20a communicating with annular spaces 22,23 defined between the walls 13,14 and 15,16 respectively. The passageways 19a, 20a also communicate with a space 24 immediately above the well 12. Three arcuate air inlets 25 are defined between the walls 13,17 and the members 19. Three further arcuate air inlets 26 are defined between the walls 14,15 and the members 20.

The walls 13,14,15,16 are formed at their upper ends with respective shoulders 13a, 14a, 15a, 16a. The shoulder 13a locates a cylindrical inner shell 27 formed throughout with a multiplicity of small

perforations 28, eg of approximately 2 mm diameter. The shoulders 14a, 15a, 16a support second, third and outer shells 29,30,31 respectively. The shells 29,30,31 are perforated in the same way as the inner shell 27.

An unperforated cylindrical shroud 32 is mounted on the outer shell 31 by means of an annular mounting flange 33 secured to the upper end of the shroud 32 as viewed in Fig. 1. The mounting flange 33 has an upwardly extending and in-turned section 34 at its inner end which rests on the upper edge of the outer shell 31. The shroud 32 is spaced from the outer shell 31 so as to define a passageway 35 for air, an inlet 36 to the passageway 35 being defined between the lower end of the shroud 32 and the wall 16. The flange 33 acts as a closure member for the passageway 35.

Two cylindrical wicks 37,38 are positioned in the annular spaces 22,23 respectively, and thereby extend around the well 12.

The base member 10 is formed with three fixing lugs 39 two only of which are shown.

In use, the burner is mounted in an appliance such as a boiler B so as to be disposed in the position shown

in Fig. 1. Diesel fuel F is fed from a supply (not shown) to the inlet 11 so as to fill the well 12 and rise to a level indicated at L. It will be noted that the oil passes through the passageways 19a, 20a to be absorbed by the wicks 37,38. The supply maintains the oil level L at all times. Fuel F on the wicks 37,38 is suitably ignited, air entering the burner as indicated by arrows A via the various inlet passageways 25,26, perforations 28 and the inlet 36 thereby providing a constant air supply.

The shells 27 to 31 are heated by the burning oil and the shroud 32 minimises heat loss from the shells so that the working temperature of the burner remains sufficiently high to burn diesel oil effectively. Also, the shroud 32 encourages a good flow of air through passageway 35 to the perforations 28 of the outer shell 31.

It will be noted that an annular outlet 40 for combustion gases is defined between the upper ends of the shells 27,29 and a similar annular outlet 42 is defined between the upper ends of the shell 30 and the outer shell 31. However, the upper end of the inner shell 27 is closed by a circular closure member 43 and an annular space defined between the upper ends of the shells 29,30 is closed by a closure member 44.

Preferably, the closure members 43,44 and the mounting flange 33 could comprise a single sheet-metal pressing which defines a plurality of vent apertures in alignment with the respective outlets 40,42. The shroud would then be suitably secured, e.g. by brazing, to the outer peripheral edge of the pressing. In that way, after placing the shells 27 to 31 in position, the metal-pressing having the shroud 32 thereon would be placed in position on the shells.

In certain cases, a baffle 45 may be mounted above the burner as shown in Fig. 1. The baffle 45 acts as a heat retainer which aids combustion of any unburned fuel in the combustion gases.

The burner of Fig. 3 is a burner in accordance with the first and third aspects of the invention. Parts corresponding to parts in Figs, l and 2 carry the same reference numerals.

In Fig. 3 an annular base member 46 has walls 47, 49 defining an annular channel 48. The base member 46 has a well 12 arranged off centre of the base member towards an edge thereof. The well 12 has an inlet port 11 for diesel oil and an outlet port 50 in an upper part thereof allowing fluid communication between the well 12 and the annular channel 48.

The walls 47, 49 have respective shoulders 47a, 49a at their upper ends. The shoulders 47a, 49a support inner and outer shells 27, 29 respectively. The shells 27, 29 are formed with a multiplicity of perforations 28 (as shown in Fig. 1) .

The inner shell 27 has an unperforated cylindrical inner shroud located therewithin and mounted thereto by means of an annular mounting flange 33a secured to the upper end of the shroud 32a as viewed in Fig. 3. The flange 33a has an upwardly extending out-turned section 34a which rests on the upper edge of the inner shell 27. The inner shroud 32a is spaced inwardly of the inner shell 27 so as to define a passageway 35a for air A. The flange 33a closes the upper end of the passageway 35a. An inlet 36a to the passageway 35a is defined between the lower edge of the shroud 32a and the wall 47.

An unperforated cylindrical outer shroud 32b is arranged around the outer shell 29. The shroud 32b is mounted on the outer shell 29 in similar manner to the way in which the inner shroud 32a is mounted on the inner shell 27. The outer shroud 32b is spaced from the outer shell 29 so as to define a passageway 35b for air. The flange 33b closes the upper end of passageway 35b. An inlet 36b for the passageway 35b is defined between the lower edge of the shroud 32b

and the wall 49.

A cylindrical wick 37 is located in the annular channel 48, so as to extend around the well 12.

A circular base restrictor 52 extends from a top wall of the well 12 across the space defined by the annular base member 46.

An annular top restrictor 54 on legs 54a is located above the opening 40 defined between the shells 27, 29. The legs 54a rest on the flange 33a.

The restrictors 52, 54 restrict flow of air through the burner. The top restrictor 54 also acts in a similar manner to the baffle 45 of Fig. 1, aiding combustion of unburned fuel in the combustion gases.

In use, the burner of Fig. 3 is mounted in an appliance such as a boiler. Diesel fuel F is fed to the well 12 from a supply (not shown) . The fuel fills the well 12 and rises within the annular channel 48 to the level indicated at L. The oil is absorbed by the wick 37 and during operation of the burner is maintained at level L.

Fuel F on the wick 37 is ignited, air entering the burner via openings 36a, 36b, up the passageways 35a,

35b and through the perforations 28 in shells 27, 29. The shells 27, 29 are heated by the burning oil and the shrouds 32a, 32b minimise the heat loss from the shells 27, 29. The burner is thus maintained at a sufficient temperature to burn diesel oil effectively.

As in the Fig. 1 embodiment an annular outlet 40 is provided between the shells 27, 29 at an upper end thereof to allow escape of combustion gases. The Fig. 3 arrangement provides a burner with better controllability at low outputs. The burner of Fig. 3 also produces a flame which burns until almost the top of the shells 27, 29 which reduces problems of carbonization.

The shells 27,29,30,31 and the shrouds 32,32a,32b are made from sheet metal such as stainless steel.

With our previous burner, we could maintain a temperature in a range of typically 500 to 570 degrees centigrade which is not sufficiently high to burn diesel fuel effectively. We have found that a burner in accordance with the invention maintains a temperature in the range 600 to 670 degrees centigrade. Such temperatures are sufficiently high to burn diesel fuel efficiently making the burners suitable for use in situations where diesel fuel is readily available.