GB2308432A - Flue blocks - Google Patents

Abstract

A flue block has an inlet in the bottom face (10), and an outlet in the top face (12) which is the same size as the inlet but in plan is offset from the inlet, and a flue passage (22) which connects the inlet and the outlet. In order that the cross section of the passage at all points along its axis and at right angles to the axis should not be less than a prescribed minimum, the flue passage is shaped to have a central portion of constant cross section inclined relative to the ends, and end portions leading to the outlet and inlet respectively, which are enlarged and shaped at one side to enable the passage to meet the adjacent end at right angles. The advantage is that the block can be of similar overall dimensions to a conventional block but can have a larger cross sectional area flue to meet the said prescribed minimum.

Description

IMPROVEMENTS RELATING TO FLUE BLOCKS This invention relates to gas flue blocks, which are blocks used one on top of another to create a gas flue through which the gaseous products of combustion from a domestic gas burning appliance can pass.

The blocks to which the present invention relates are rectilinear in nature, and are sized to meet certain standards, as laid down by British Standards, in particular, BS 1289 1986. The said British Standard specifies that the flue passage which passes through each block, must be of a cross-sectional area of a minimum of 16,500 mm2 and this has been followed by manufacturers for some years, but in relation to some types of blocks, a problem has been identified in that a new European Standard is being prepared which specifies that the cross-sectional area still has to be a minimum of 16,500 mm2 but the area in question has to be measured in a direction at right angles to the centre line of the passage through the block.

The particular blocks are those known as the offset blocks as in these blocks, the passage lies at an angle (which is limited to a maximum of 30 degrees to the vertical under the British Standard) relative to the height direction of the block. To explain further, each block has a top face. a bottom face, a front face, a back face, and two end faces. The height is less than the width, but is selected to fit in with the course size of the bricks or other components which are used for the walls of the building in which the flue is to be constructed. The depth of the block again is less than the width and again is selected to match the thickness of the walls of the building.

In all of the blocks to which the invention relates, the passage through the block extends from an inlet in the bottom face to an outlet in the top face, the area of the inlet being equal to that of the outlet.

A first type of offset block is known as a lateral offset block, in which the passage, of rectangular configuration and defined by straight comers, lies at an angle (which must be no greater than a predetermined angle) to the sides of the block, so that looking at the block in plan view, the passage outlet in the top face is "offset" in relation to the passage inlet in the bottom face, by an amount dictated by the height of the block and the angle of the passage. In such arrangement, the centre line of the passage is a straight line extending from the centre of the passage inlet to the centre of the passage outlet.If, as is required by the British Standard the area of the inlet and outlet is 16,500 mm2 or slightly greater as some manufacturers prefer, then if the angle of inclination of the passage is 30 degrees or something close thereto, then the cross-sectional area of the passage, measured at right angles to the axis of the passage significantly smaller than the required amount (specifically 16,500 mm2) and these blocks will not therefore meet the new proposed revised European Standard.

By the same reasoning, it can be shown that the blocks known as "backset" blocks also will not meet the new proposed revised European Standard. In backset blocks, the passage inclines from the front face to the back face of the block.

In order to over come this problem, the obvious choice would be to increase the size of the passage, but that brings its own problems in that there is another requirement that these blocks must have a minimum thickness which is currently 25 mm, and to increase the passage size would mean increasing the overall size of the block. This throws up further disadvantages. In particular, the amount of material for the block is increased, and secondly, the increase in size of the block could make it unusable in the brickwork of the building in which the flue is to be installed.

The present invention provides a solution in a simple and effective way, without increasing the size of the block, and without contravening the requirements for maintaining a minimum thickness.

According to the invention there is provided a gas flue block wherein the passage is angled from the bottom face to the top face, and wherein, in order to maintain the cross-section of the passage constant or substantially so, the passage comprises a central parallel sided portion at the respective ends of which are similar, opposite handed segmental portions including curved or angled surfaces of the passage which curve tangentially or approximately so from the parallel sided portion to meet the top face and bottom face respectively at right angles.

By this means, the passage cross section, at any point along the central axis of the passage, and measured at right angles thereto, is constant or substantially so. Furthermore, there is no need to increase the overall size of the block, and there is no need to deviate from the minimum thickness requirement.

The invention is further explained with reference to the accompanying drawings, which are to scale and wherein; Fig. 1 is an isometric view of a lateral offset block according to the invention; Fig. 2 is plan of the block shown in Fig. 1; Fig. 3 is a sectional side view of the block shown in Fig. 1; Fig. 4 is a sectional front view of the block shown in Fig. 1; Fig. 4A is a view similar to Fig. 4, but shows a modified arrangement; Figs. 5, 6, and 7, respectively are a front, top and sectional side views of a backset block according to the invention; and Figs. 8, 9 and 10 are views similar to Figs. 5 to 7, but showing an alternative form of backset block according to the invention.

Referring to the drawings and firstly to Figs. 1 to 4, the block illustrated is constructed from the conventionally used material for these gas flue blocks and the dimensions indicated in the drawings have been included as they are ones which are typically employed. However, it is not intended that the invention should be limited either it terms of material used or dimensions employed.

As shown in Fig. 1, the block is rectangular, and, having regard to the manner in which these blocks are used, the block has a bottom face 10, a top face 12, a front face 14, a rear face 16, a left side face 18 and a light side face 20. If the block is required to cause the flue to divert to the left instead of to the right as shown in the Figs., the left side face 18 becomes the right side face 20 and vice versa. The flue passage 22 extends from an inlet 24 in the bottom face 10 through the block to an outlet 26 in the top face 12, and the passage 22 is rectangular in crosssection, as shown clearly in Fig. 2. This Figure also shows that the outlet 26 is offset in relation to the inlet 24 when viewed in plan, and this in use is to enable the flue to follow a path which can deviate from a straight vertical path, in order to accommodate, for example, the building's construction.

Surrounding the outlet on the top face is a spigot rim 28, which is for engaging a socket recess 30 in the bottom face of the block to be superimposed thereon when the blocks are used to form a flue. This prevents relative lateral slipping of the blocks when being stacked and thereafter.

In the conventional blocks of this type the passage is formed by simply connecting the corners of the inlet 24 to the corners of the outlet 26 by straight lines, but as explained herein, this construction does not meet the new proposed revised European Standard. In the block according to the invention, however, the passage is inventively shaped so that the block can meet this Standard, without increasing its overall size.

Therefore, referring to Fig. 4, the passage is made up of a central parallel sided portion 32, flanked on the ends by segmental portions 34 and 36 respectively at the bottom and top of the block. These portions 34 and 36 face in opposite directions and the curved surfaces 38 and 40 thereof are tangential to the adjacent surfaces 42, 44 of the parallel sided portion 32, and then curve to meet the bottom and top faces 10, 12 at right angles. By this arrangement it will be understood that the cross-section of the passage 22 at any point along its central axis 46, and measured in a direction at right angles to the said axis, of which examples are given at positions A, B mid C, will be constant. This enables the block to give a smooth flow characteristic, and to meet the new Standard, without the size of the block having to be increased.

In the arrangement in Fig.4A, which is almost identical to that in Fig. 4, and the same reference numerals have been used, but instead of the surfaces corresponding to 38 and 40 being curved, they are defined by angled portions 38A; 38B, and 40A; 40B as shown. Adopting this geometry means that the cross-section of the passage increases at the regions 39 and 41, but the increase is minimal and in any case a slight increase can be tolerated, as long as the cross-section of the passage, measured as above, does not fall below the specified minimum.

The principle can be applied to other blocks which have an offset in the flue passage, and two examples are given in Figs. 5 to 7 on the one hand, and Figs. 8 to 10 on the other hand. These blocks are of the "backset" type and the flue passage is offset from front to rear, or vice versa, -rather than from side to side in the case of the block shown in Figs. 1 to 4. It is felt that no further specific description is needed for the reader to understand the construction of the blocks in Figs 5 to 10, but to assist, the reference numerals which have been used in these Figures are the same as those which have been used in the previous Figures to indicate the parts which serve the same function as the corresponding parts in Figs 1 to 4.

The only significant feature of the block of Figs 5 to 7 which should be mentioned is that the rear face 16 is sloped rearwardly in a direction from top to bottom, and this indicates that the invention can be applied to blocks which are not exactly rectangular, but rather are based on this shape.

In the block of Figs. 8 to 10, the top face 12 has a rebate 50 at the front thereof to save material.

The invention provides a particularly effective method of arranging for gas flue blocks to meet new standards without requiring any increase in block size, and avoiding the difficulties precipitated by increasing block size, as discussed herein.

Claims (2)

1. A gas flue block wherein the passage is angled from the bottom face to the top face, and wherein, in order to maintain the cross-section of the passage constant or substantially so, the passage comprises a central parallel sided portion at the respective ends of which are similar, opposite handed segmental portions including curved or angled surfaces of the passage which curve tangentially or approximately so from the parallel sided portion to meet the top face and bottom face respectively at right angles.

2. A gas flue block substantially as hereinbefore described with reference to the accompanying drawings.