GB2541452B - An oven - Google Patents

Description

An oven

The present invention relates generally to an oven and finds particular, although not exclusive, utility as a portable, domestic garden oven.

Rocket ovens typically burn solid fuel, such as wood, and include a flue to enable resulting gases to completely burn before reaching a cooking area.

Such ovens tend to be relatively simple and it is desirable to have a more sophisticated oven which includes several features which cumulatively promote efficiency and environmental benefits, and provide an improved cooking facility.

In one aspect, the present invention provides an oven including a fuel chamber, a cooking chamber located within a heat transfer chamber, and a flue for directing gases from the fuel chamber to the heat transfer chamber, wherein the fuel chamber has an inlet, for accepting fuel, which has a cross-sectional area which is substantially greater than the cross-sectional area of the flue, and wherein a heat spreader plate is arranged in the heat transfer chamber between the end of the flue and the cooking chamber, the oven being arranged such that the flue extends from the fuel chamber towards the heat transfer chamber in a first direction which is inclined between vertical and horizontal axes.

In use, fuel such as wood may be placed in the fuel chamber and burnt therein. Due to the nature of such ovens plenty of air needs to be able to enter the fuel chamber during burning. In the prior art such fuel chambers tend to have an inlet which has the same cross-sectional area as the outlet (into the flue) such that with fuel in the fuel chamber the cross-sectional area of free space is reduced thus reducing the amount of air which can enter. The present invention, however, due to its conical nature allows for sufficient air to enter the fuel chamber, even with fuel present, to allow complete combustion of the gases created from the burning of the fuel within the oven before they exit via the chimney. This complete combustion is also permitted by the relatively long flue.

This complete burning, together with other features described herein, creates a relatively high temperature and the presence of the heat spreader plate is therefore required to spread the heat across the floor of the cooking chamber to avoid the generation of hot spots in it.

The oven is arranged such the cooking chamber is isolated from the heat transfer chamber so that none of the combustion gases reach inside the cooking chamber. This feature allows for food to be cooked but not tainted by any of the gases.

The flue is arranged to be long enough to ensure the gases fully combust on their way from the fuel chamber to the heat transfer chamber. However, to keep the overall size of the oven to a minimum the flue is arranged to be inclined between the horizontal and vertical axes. This may be at approximately 45 degrees above a horizontal plane, such a plane coinciding with the base of the oven.

In this regard, the oven may be portable and may include handles either side for moving it. The overall dimensions of the oven may be approximately 730mm high by 430 mm deep by 570mm wide.

The oven may comprise an outer housing within which the heat transfer chamber and fuel chamber are arranged, the outer housing being configured such that a void is maintained substantially around the heat transfer chamber at the front, back, sides, top and bottom, for receiving insulation.

As mentioned above, it was found that the temperature of the gases exiting the flue into the heat transfer chamber created a hot spot in the floor of the cooking chamber and so die spreader plate has been included. This spreads die heat more evenly across the door of the cooking chamber. The spreader plate may comprise a mild steel plate suspended in the void between the heat transfer chamber and cooking chamber. In this respect, the heat transfer chamber may be defined by a walled enclosure connected at one end to the due from the fuel chamber and including an oudet for the gases to disperse to the atmosphere.

The oven may comprise insulation within the housing in the said void. The insulation may be in the form of a blanket around the top, sides, front and back of the heat transfer chamber in the said void. Underneath the heat transfer chamber loose particulate insulation may be provided. For instance, vermiculite may be inserted into the void between the outer housing and the underside of the heat transfer chamber such that it fills the space around the flue and fuel chamber. The fuel chamber connects to the outer housing and an aperture is provided in the outer housing at this point to provide the fuel chamber inlet for positioning fuel, in use.

The oven may include a food aperture in the cooking chamber, a coincident door aperture in the outer housing and a door for covering the door aperture in the outer housing. In this way the door may be kept closed while the cooking chamber reaches the correct temperature, the door then being opened, food being placed within, and the door being closed thereafter. Food may be withdrawn via the door aperture with the door opened. A flange may extend between the cooking chamber and the outer housing to prevent any insulation present in the void from escaping, in the vicinity of the oven aperture. This is necessary due to the void maintained between the outer housing and the cooking chamber at the front of the oven. Without such a flange insulation could escape and/or food detritus would collect in the void, both of which are undesirable.

The oven may include a chimney arranged above, and connected to, the heat transfer chamber and including a baffle at its upper outlet. The baffle may be designed and/or arranged to control the flow of gases exiting from the channel, for instance to throttle the volume flow-rate. It may also act as a wind shield to prevent drafts from affecting the gas flow out of the chimney, and/or to prevent blow-back, and/or prevent foreign matter ingress. A flange may extend between the heat transfer chamber and the chimney to prevent gases from the fuel chamber entering the void. It will also prevent any insulation present in die void blocking die chimney.

The heat transfer chamber and cooking chamber may both have an arch shape. In this respect, the door aperture and fuel chamber inlet may be arranged under the arch.

The oven may include ribs at a base of the cooking chamber. These may act to strengthen the floor of the cooking chamber and prevent buckling thereof, due to the heat.

The oven may include fire bricks arranged within the ribs. These may form the surface on which food may be cooked. The bricks may be removably insertable allowing replacement as necessary.

The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

Figure 1 is a perspective view of an oven;

Figure 2 is cross-sectional schematic side view through the oven;

Figure 3 is a cross-sectional schematic plan view of the fuel chamber;

Figure 4 is cross-sectional schematic elevational view of the upper part of the oven;

Figure 5 is a cross-sectional schematic elevational view of part of the base of the cooking chamber; and

Figure 6 is a plan view of part of the base of the cooking chamber.

The present invention will be described with respect to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. Each drawing may not include all of the features of the invention and therefore should not necessarily be considered to be an embodiment of the invention. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

The principles of the invention will now be described by a detailed description of at least one drawing relating to exemplary features of the invention. It is clear that other arrangements can be configured according to the knowledge of persons skilled in the art without departing from the underlying concept or technical teaching of the invention, the invention being limited only by the terms of the appended claims.

In Figure 1, an oven 10 is depicted having a substantially planar front surface 20, a substantially planar rear surface 30 (not shown). Either side 40 of the oven extends upwardly from the base of the oven 10 towards the top of the oven in a vertical plane. The base of the oven is approximately rectangular.

The two opposing sides 40 arch inwardly and meet at the top 50 of the oven. A chimney 60 projects vertically upwardly from the top 50 of the oven 10.

In the front planar surface 20 two apertures are provided. The first, located towards the base of the oven 10, is for accessing the fuel chamber 70. The fuel chamber 70 is four sided with a constant height but a width which narrows as its depth increases into the oven 10. At the far end of the fuel chamber 70 a flue is arranged as will be described in more detail below.

The second aperture 82, located towards the top 50 of the oven 10 is for accessing the cooking chamber 80. The aperture 82 is arch shape and has a door (90 in

Figure 2), hung on a side hinge, which opens outwardly and in a closed position seals the aperture 82.

Inside the cooking chamber 80 fire bricks 100 are arranged in a grid in between ribs which extend across the floor of the cooking chamber 80. A cross-sectional schematic view of the oven 10 is shown in Figure 2. The front 20 of the oven is depicted on the right hand side including the aperture for the fuel chamber 70 towards the lower end and the aperture 82 for the cooking chamber 80 towards the upper end. The upper aperture 82 is shown covered by a closed door 90. The arrangement of the flue is visible in that a section 72 of it extends away from the back 71 of the fuel chamber in an inclined upward direction reaching a short section 73 which heads vertically upwards to the base of the heat transfer chamber 130.

The flue 72, 73 has a rectangular cross-section (perpendicular to its bore).

The cooking chamber 80 is surrounded by the heat transfer chamber 130 such that a gap therebetween of approximately 10 to 40mm, preferably 25mm, is maintained around its arched sides, top and bottom but not its front or rear surfaces. The top of the flue 73 meets the heat transfer chamber 130 at the base thereof and directly underneath the cooking chamber 80. A heat spreader plate 132 is provided in the gap 129 between die base of die cooking chamber 80 and the base 86 of the heat transfer chamber 130. It is arranged between the oudet of the due 73 and the underside of the cooking chamber 80. The heat spreader plate is a rectangular sheet of mild steel having an approximate thickness of 3mm. The heat spreader plate may also be described as a gas distribution plate.

The fire bricks 100 and ribs 110 are visible at the base of the cooking chamber 80.

The chimney 60 at the top of the oven 10 connects to the heat transfer chamber 130 above the top of the cooking chamber 80. The chimney 60 includes a baffle 65 to mitigate against downdraughts and the like. A flange 85 is visible connecting the cooking chamber’s aperture 82 with the front 20 of the outer housing of the oven 10. In this way any insulation located be tween the heat transfer chamber and the outer housing cannot fall out, and food cannot enter the void. The base 86 of the heat transfer chamber 130 extends from the front 20 to the rear 30 of the outer housing and extends from side 40 to side 40. This acts to separate the upper part of the oven 10 from the lower part of the oven. A void 135 is maintained between the heat transfer chamber 130 and the inside of the oven’s outer housing 20, 30, 40 around its top, front, rear and sides. In this void 135 insulation, such as a blanket-type insulation called Superwool (RTM), may be placed to insulate the heat transfer chamber and improve the oven’s efficiency. The blanket may have a thickness of approximately 20mm to match the width of the gap between the inside of the outer housing 40, 50 and the outside of the heat transfer chamber 130.

The heat transfer chamber 130 is defined by a base 86, underneath the cooking chamber 80, an arched upper part which extends from the base 86 on one side of the cooking chamber 80 to the other side, and a front 22 and rear panel 32 each of which extends from the base 86 to the limits of the arched upper part. In this way it creates a sealed void 130 with only one inlet 73 and outlet 60.

In the lower half of the oven (defined by the portion beneath the heat transfer chamber 130) another void 75 is maintained defined by the base, front 20, rear 30 and sides 40 of the oven and the base 86 of the heat transfer chamber 130.

This void 75 may be filled with loose particulate insulation such as vermiculite so as to insulate the flue and heat transfer chamber and thus improve the oven’s efficiency.

The particulate insulation material is unable to escape via the fuel chamber because the mouth of the fuel chamber is sealed against the inside of the front surface 20 of the oven 10.

Figure 3 shows a plan view of the fuel chamber 70. At the lower end of the Figure the mouth 71a can be seen sealed against the inside of the front surface 20 of the oven 10. The mouth 71a has a first dimension of approximately 180mm by 120mm. As the fuel chamber extends inwardly (upwardly in the Figure) its width decreases until it reaches a width 71b having a cross-sectional area of approximately 45% of the cross-sectional area of the mouth 71a.

Figure 4 is a cross-sectional schematic view looking from the front to the back of the upper portion of the oven 10 (being defined by the portion from the base 86 of the heat transfer chamber 130 upwards). The chimney 60 is not shown.

The arched top 50 of the oven 10 is shown extending downwardly to each side 40. A portion of the chimney 60 is shown in broken lines. The heat transfer chamber 130 is shown around the cooking chamber 80 with a gap therebetween to allow the circulation of gases. The void 135 is shown between the inside of the top 50 of the oven and the top of the heat transfer chamber 130 for insulation to be placed (not shown).

Also visible is the mouth 82 of the cooking chamber 80, shown in broken lines, the top 73 of the flue 72 as it meets the bottom of the heat transfer chamber 130 and the heat spreader plate 132.

In Figure 5 a rib 110 is shown together with a portion of two fire bricks 100. The rib is an upside-down “T” shape providing support for, and separation of, the two bricks 100. Each rib has a vertical portion 110a and a horizontal portion 110b. The vertical portions 110a help to maintain the horizontal position of the fire bricks in the floor and the horizontal portions 110a act to support the bricks 100.

The ribs 110 help to prevent the floor of the cooking chamber 80 buckling due to the intense heat and are therefore, in one sense, reinforcing ribs. In one embodiment, the cooking chamber may have a steel floor underneath these bricks 100 but without the ribs 110. In another embodiment, the ribs 100 may be present as well as the steel floor, however, the ribs 110 may only include the vertical portions 110a, or may include both vertical 110a and horizontal 110b portions. In one embodiment, the floor may only have the ribs and bricks without the steel floor. A plan view of a portion of the ribs 110 and bricks 100 is shown in Figure 6 where it can be seen that the ribs 110 may extend in a grid-like pattern to provide support to each brick 100 about their entire circumference so as to act as a seal and prevent gases from reaching the cooking chamber 80 in a version of the oven 10 which does not include a steel floor. There may be more than one brick in each cell of the grid. These bricks may lie adjacent one another. They may have overlapping edges to assist in sealing the floor to prevent the ingress of gases, necessary if there is no separate steel floor underneath the cooking chamber. Other alternative means for interlocking adjacent bricks are contemplated such as tongue and groove connections along their sides.

With reference to the above Figures, in use, fuel (such as wood) is placed in the fuel chamber 70 and burnt therein. Due to the relatively wide mouth 71a air can easily enter the fuel chamber 70 to allow the combustion to take place. The fuel itself does not completely block the entrance to the flue 71 due to the fuel chamber having a greater cross-sectional area than flue 71, 72. Adequate air supply is important to allow the gases produced by the burning fuel to completely burn as they pass up the flue 71, 72. In this way, substantially complete combustion takes place such that very little smoke or environmentally harmful compounds (such as nitrous oxides, sulfur dioxides and CO) is emitted from the top of the chimney.

The hot gases flow up through the oven 10 to the chimney by virtue of their heat and the stack effect. The gases pass through the heat transfer chamber 130 around the cooking chamber 80 (in the directions shown by the arrows referenced “A” in Figures 2 and 4) and thus heat the latter. The heat spreader plate 132 above the top of the flue 73 ensures that an intense hot spot is not generated in the centre of the floor of the cooking chamber 80.

The fire bricks 100 further help to spread the heat within the base of the cooking chamber 80. They also act to store heat and release it more slowly than the metal of the oven 10.

The gases pass out via the chimney 60 after passing through the heat transfer chamber 130.

The insulation in the voids 75, 135 acts to improve the efficiency of the oven 10 and allow for temperatures of 400C to be generated in the oven with only a small amount of wood kindling type fuel.

Food placed in die cooking chamber 80 may be cooked dierein. Food such as pizzas, meat, stews, pies, and the like may be cooked with ease using the oven 10. The oven 10 may also be used as a simple outside heat source without producing unpleasant smoke such as other outside wood burning heat sources produce.

Claims (10)

1. An oven including a fuel chamber, a cooking chamber located within a heat transfer chamber, and a flue for directing gases from the fuel chamber to the heat transfer chamber, wherein the fuel chamber has an inlet, for accepting fuel, which has a cross-sectional area which is substantially greater than the cross-sectional area of the flue, and wherein a heat spreader plate is arranged in the heat transfer chamber between the end of the flue and the cooking chamber, the oven being arranged such that the flue extends from the fuel chamber towards the heat transfer chamber in a first direction which is inclined between vertical and horizontal axes.

2. The oven of claim 1, comprising an outer housing within which the heat transfer chamber and fuel chamber are arranged, the outer housing being configured such that a void is maintained substantially around the heat transfer chamber at the front, back, sides, top and bottom, for receiving insulation.

3. The oven of claim 2, comprising insulation within the housing in the said void.

4. The oven of either one of claim 2 and claim 3, including a food aperture in the cooking chamber, a coincident door aperture in the outer housing and a door for covering the door aperture in the outer housing.

5. The oven of claim 4, wherein a flange extends between the cooking chamber and the outer housing to prevent any insulation present in the void from escaping, in the vicinity of the oven aperture.

6. The oven of any preceding claim including a chimney arranged above, and connected to, the heat transfer chamber and including a baffle at its upper outlet.

7. The oven of claim 6, dependent directly or indirectly on claim 2, wherein the heat transfer chamber is a sealed void with only one inlet and outlet, wherein the inlet is the flue and the outlet is the chimney, such that gases from the fuel chamber are prevented from entering the void between the heat transfer chamber and the outer housing.

8. The oven of any preceding claim, wherein the heat transfer chamber and cooking chamber both have an arch shape.

9. The oven of any preceding claim including ribs at a base of the cooking chamber.

10. The oven according to claim 9, including fire bricks arranged within the ribs.