IES950980A2 - Conversion oil burner - Google Patents

Abstract

A pressure jet oil burner for use in converting a solid fuel cooker/heater to oil consists of a housing made of die cast metal, and an arrangement in which the impeller motor is beneath the impeller and the blast tube is on the opposite face of the housing to the motor. The burner is preferably manufactured by starting with a commercially available burner intended for oil-fired central heating in which the components are mutually configured as described and modifying the burner so as to fit within the narrow confines of an ash pit.

Description

CONVERSION OIL BURNER Field of the Invention The present invention relates to a pressure jet conversion oil burner. By conversion oil burner is meant a burner used in the conversion of a cooker or stove from solid fuel to oil.

Prior Art Pressure jet oil burners for burning oil to generate heat have been known for many years and are used in a variety of situations including for oil-fired central heating. A pressure jet oil burner includes the following important components: (a) a housing; (b) a blast tube associated with the housing; (c) an impeller mounted in the housing blast tube; and for driving air out through the OPEN TO PU6UC INSPECTION UNDER SECTION 26 AND RULE 23 JNL. No.../.?.?#.....OF ^950980 - 2 (d) an electric motor which drives the impeller.

Pressure jet oil burners have been used when converting cookers or stoves from solid fuel to oil. By a cooker in this context is meant an apparatus which burns fuel so as to generate heat for domestic cooking, space heating and, usually, water heating purposes. Cookers are typically installed in the kitchen of a private dwelling and consist of a number of chambers including a combustion chamber, an ash pit below the combustion chamber and one or more oven chambers. In recent years it has been commonplace to convert such cookers from solid fuel to oil. The principal reason for such conversion is because of a change in the relative prices of solid fuels on the one hand and oil on the other hand. Also, oil is easier to use. Solid fuel must be transported to the home, stored, loaded into the cooker, and the ashes must be cleared out, whereas oil may be piped to the cooker from a storage tank. Furthermore, oil is generally cleaner. When using solid fuel it is necessary to carry the solid fuel through the kitchen and carry the ashes out of the kitchen, whereas incoming oil is piped and the combustion residues are exhausted to atmosphere. There is a widely used method of carrying out conversion using a pressure jet oil burner. This method includes the steps of installing the burner in the ash pit so as to direct the air and oil mixture from the ash pit into the combustion chamber directly above where combustion takes place.

The burner is usually surrounded by noise insulating material to reduce the noise associated with these devices.

The currently existing range of central heating pressure jet oil burners does not include any burner suitable for use across the range of typical conversion applications. In particular no burner has been found which together with noise insulation material is small enough to fit within the narrow confines of ash pits having widths across the range of typical ash pit widths such that after conversion the blast tube of the burner is approximately centrally located in relation to the width of the ash pit. By central heating burner or central heating pressure jet burner is meant a burner which is commercially available for use in an ordinary central heating system. If a sufficiently small central heating pressure jet oil burner in the usual geometric configurations could be found it probably would not have the requisite «509 8 I - 3 heat output. Accordingly, conversion of heating apparatus as described above has been carried out using pressure jet oil burners which have been custom designed for this purpose. A number of manufacturers have produced such custom designed pressure jet oil burners, sometimes called conversion burners. These are characterised by special geometric arrangements of their components to accommodate the ash pit dimensions. The width is usually the most problematic dimension. The blast tube directs the air and the oil mixture upwardly into the combustion chamber of the conversion cooker. The housing is a fabricated steel housing. The housing accommodates the impeller and also serves as a support framework for the main components including the motor and the blast tube.

A conversion burner of this type is disclosed in Irish Patent Specification No. 56250 (Morris et al.) filed on 3rd June, 1988. In the Morris et al. conversion burner the pump, motor and impeller are mounted in the usual co-axial configuration thus providing a convenient arrangement whereby the motor can drive the impeller and the pump. The axis of the pump motor and impeller extends horizontally from the front to the rear of the ash pit, thus making use of the greatest dimension of the ashpit, with the pump being mounted at the front, the motor in the middle and the impeller at the rear. A fabricated steel housing also extends horizontally from the front to the rear of the ashpit and is disposed directly above the pump and above the motor but with a downward extension at the rear thereof to enclose the impeller. The fan, comprising the impeller and housing, draws air into the housing through perforations in the rear wall of the downward extension, the air is then driven vertically up into the main part of the housing and then horizontally along the housing from the rear to the front and then undergoes a further change in flow direction of about 135° so as to exit through a blast tube mounted from the side of an upper extension of the housing and angled rearwardly and upwardly.

Object and Summary of the Invention A principal object of the present invention is to provide an improved conversion pressure jet oil burner.

L«50® - 4 The present invention provides a pressure jet oil burner which is narrow in width and suitable for use in a conversion cooker or stove and includes the following components: (a) a housing; (b) a blast tube associated with the housing; (c) an impeller mounted in the housing for driving air out through the blast tube; (d) an electric motor which drives the impeller; characterised in that (e) the housing comprises one or more metal die castings; (f) the motor is beneath or substantially beneath the impeller; and (g) the blast tube is on the opposite face of the housing to the motor.

The burner as described has several advantages over the conversion burners of the prior art, including the following. Firstly, it has a lower unit manufacturing cost because the relatively expensive fabricated steel housing is replaced by a die cast housing. Secondly, the die cast housing is of greater dimensional consistency than the fabricated type and will thus be less prone to problems with the operation of the fan and regulation of the air supply. Thirdly, the die cast type provides smoother transformations in the air passages than can be achieved with the fabricated type and this helps to minimise noise and turbulence.

Preferably the overall width does not exceed 175 mm and the diameter of the impeller does not exceed 100 mm.

Preferably the burner includes an air inlet passage including a slot section, and a damper assembly for regulating the flow of air through the inlet passage, the damper assembly comprising a plunger and - 5 950980 bush, whereby the plunger can be advanced into the slot section or retracted out of the slot section to thus regulate the flow.

The invention also provides a method of manufacturing a pressure jet oil burner comprising starting with a commercially available pressure jet oil burner of suitable rating intended for central heating purposes in which the housing comprises one or more metal die castings, the motor is beneath or substantially beneath the impeller when the blast tube faces vertically upwardly, and the blast tube is on the opposite face of the housing to the motor, the method being characterized by carrying out the step of cutting away or removing part of the metal die cast housing external to the impeller housing and air passage to the blast tube.

The manufacture of burners according to the invention by modifying existing suitable central heating burners is particularly advantageous. Production of die cast housings involves an initial high capital expenditure to produce the necessary dies but a low marginal cost for each additional unit produced. In the field of oil-fired central heating very large volumes of pressure jet oil burners are manufactured and sold and accordingly the commercially available burners are available at a relatively low price. Modification of burners intended for oil-fired central heating allows these economies of scale to be extended to conversion burners irrespective of the level of demand for conversion burners.

Brief Description of the Drawings The invention will now be described more particularly with reference to the accompanying drawings which show, by way of example only, one construction of burner according to the invention and a preferred method of manufacturing the boiler. In the drawings: Figure 1 is a simplified side view of the burner mounted on a support stand so that the blast tube fires vertically upwardly; Figure 2 is similar to Figure 1, but showing the burner arranged on the stand so that the blast tube fires angularly upwardly; 950980 - 6 Figure 3 is a simplified plan view of the burner with the support stand omitted; Figure 4 is similar to Figure 3, but with the damper cover plate and damper assembly removed; Figure 5 is similar to Figure 4, but with the blast tube and die cast housing cover also removed; and Figure 6 shows the manner in which a commercially available pressure jet oil burner for central heating purposes may be modified to produce a burner as shown in Figures 1 to 5.

Detailed Description of the Preferred Embodiment Referring now to Figure 1 to 5, the burner is shown in simplified form. The burner 1 comprises a two part metal die cast housing made up of a housing cover 2 and housing base 3 which provide an impeller housing, air passages and supports for many of the components. A blast tube 4 is mounted on the housing cover 2 and encloses a nozzle 5 through which pressurised oil is sprayed for combustion. A damper cover plate 6 is mounted above the housing cover 2 and forms an air inlet passage 16 to an air inlet hole 11 leading into the centre region of the fan impeller 14. The size of the air passage 16 can be regulated by a damper assembly 8 which comprises a damper plunger 7 and a damper bush 9, whereby the damper plunger 7 can be advanced into or retracted out of the slot formed between the upper impeller casing 10 and the damper cover plate 6 to thereby regulate the cross sectional area of the air inlet passage 16. The damper plunger 7 and damper bush 9 may be threaded or plain and may be locked by means such as a locking nut or screw which are not shown. The impeller casing is formed in two parts and comprises an upper impeller casing 10 and a lower impeller casing 13 which form integral parts of the housing cover 2 and housing base 3 respectively. The top of the upper impeller casing 10 is set below the level of the top of the housing cover 2 such that an air inlet passage 16 is formed above the impeller casing and communicates with it through the air inlet hole 11. Quiet and efficient air flow into the impeller centre is assisted by an air inlet guide 12 which • 50980 * - 7 forms an integral part of the housing cover 2. Air passes from the impeller casing to the blast tube 4 via an air outlet passage 15 to the blast tube. The impeller 14 is driven by an electric motor 17 which is mounted on the lower side of the housing base 3. The motor 17 also drives an oil pump 18 which delivers oil to the rear of the nozzle assembly 20 through an oil line 19. The housing is supported on a stand 21. For simplicity, various small components, including wiring; ignition electrodes; motor capacitor; control box; transformer and photoelectric sensor are not shown in the Figures.

The burner is of narrow width, the width being less than 175 mm. The impeller is of small diameter, the diameter being less than 100 mm.

The burner may be arranged on the support stand 21 as shown in Figure 1 with the blast tube firing directly upwards or as shown in Figure 2 with the blast tube firing upwards but angled towards the rear of the combustion chamber. The optimum firing angle will depend on the geometry of the combustion chamber and ash pit of the cooker.

The metal die cast housing of the burner is adapted from the housing of a specific type of burner used with a central heating boiler. Although the die cast housing may be purpose-made for the conversion burner, adaptation of existing die cast components has an advantage when production numbers are relatively small as it eliminates the cost of die cast tools. The specific type of central heating boiler burner suitable for adaptation must have the following characteristics. Firstly, it must comprise metal die castings to form the impeller housing and an air outlet to the blast tube. Secondly, the blast tube must be on the opposite face of the impeller housing to the motor. This feature is absent on most central heating boiler burners. Thirdly, the burner must comprise a fan impeller of relatively small diameter. This feature is also absent on most central heating boiler burners.

The housing of the specific type of central heating boiler burner consists of two complex complementary die castings which when assembled form various functional parts including the impeller and air passage cavities. The unadapted housing is unsuited for use in conversion - 8 L95¢9 go cookers because it does not fulfil the requirement for narrow width. However, the requirement can be met if the housing is trimmed to remove material which lies outside two vertical parallel planes. The two planes are selected so as to enclose between them the impeller housing and air passage outlet to the blast tube and so as to lie as close as possible to the outside of the walls of the impeller housing and lie approximately equidistant from the nozzle. Trimming may be carried out conveniently with a vertical bandsaw machine. The distance between these parallel planes determines the critical width of the resulting conversion burner and corresponds to the space available between the side walls of the cooker ash pit with due allowance being made for noise insulation material on each side of the burner.

The parallel planes are seen edge-on as lines x-x and y-y in Figure 6. The cut may be a straight cut co-incident with line x-x or may follow the contour of the casing as shown in Figures 3 to 5.

Figure 6 also shows a further parallel plane z-z which corresponds to a cut in the housing cover but not in the housing base. The purpose of this cut is to remove additional material to provide space for the damper assembly. The material removed by this cut is also external to the impeller casing and air passage to the blast tube.

The invention is not to be construed as limited to the specific embodiment(s) described herein which are given by way of example only, but instead encompasses all subject matter falling within the scope of the appended claims.

Claims (5)

1. A pressure jet oil burner which is narrow in width and suitable for use in a conversion cooker or stove comprising: (a) a housing; (b) a blast tube associated with the housing; (c) an impeller mounted in the housing for driving air out through the blast tube; (d) an electric motor which drives the impeller; characterised in that (e) the housing comprises one or more metal die castings; (f) the motor is beneath or substantially beneath the impeller; and (g) the blast tube is on the opposite face of the housing to the motor.

2. A burner according to claim 1 in which the overall width does not exceed 175 mm and the diameter of the impeller does not exceed 100 mm.

3. A burner according to claim 1 or claim 2 including an air inlet passage including a slot section, and a damper assembly for regulating the flow of air through the inlet passage, the damper assembly comprising a plunger and bush, whereby the plunger can be advanced into the slot section or retracted out of the slot section to thus regulate the flow.

4. A method of manufacturing a pressure jet oil burner according to any of the preceding claims comprising starting with a commercially available pressure jet oil burner of suitable rating intended for central heating purposes in which the housing comprises one or more metal die castings, the motor is beneath or substantially beneath the impeller when the blast tube faces vertically upwardly, and the blast §^0980 10 tube is on the opposite face of the housing to the motor, the method being characterized by carrying out the step of cutting away or removing part of the metal die cast housing external to the impeller housing and air passage to the blast tube.

5. A burner substantially as herein described with reference to and as shown in any of the accompanying drawings. η