GB2145212A - Chimney structures - Google Patents

Abstract

A chimney structure having a plurality of pre-cast inner sections (12) stacked one above another to form a flue pipe, a plurality of pre-cast outer sections (10) also stacked one above another and surrounding the inner sections (12) and means, such as an infill material (13), retaining the inner and outer sections against relative lateral movement and serving as an insulating medium. The inner sections (12) are suitably joined together by a mechanical clamp (29) encircling the inner sections across their join. The chimney structure may incorporate a fixing system which ensures that the chimney structure is securely fastened to an adjoining wall. The chimney structure may also include access for cleaning or ancillary flue pipes. <IMAGE>

Description

SPECIFICATION Improvements in chimney structures This invention relates to a chimney structure formed from precast units.

The increasing use of domestic heating systems, especially those using solid fuel, has shown the need for better quality chimneys and in particular for chimneys that may be erected more quickly and with less margin for error than present chimneys.

Accordingly, the present invention provides a chimney structure comprising a plurality of pre-cast inner sections stacked one above another to form a flue pipe, a plurality of pre-cast outer sections also stacked one above another and surrounding the inner sections, and means retaining the inner and outer sections against relative lateral movement.

Solid fuel burning appliances are almost all dependent on natural draught, i.e., the force of convection, for their operation. This force may be impaired, thereby impairing the performance of the appliance, if the chimney loses heat too rapidly, due to poor insulation, or if there are air leaks or undue frictional resistance due to poor construction.

The embodiment of the present invention results in a chimney structure that provides a high degree of insulation while a novel concrete mixture provides a better resistance to high internal temperatures and a better resistance to the ingress of damp than has previously been possible with precast concrete chimneys. The embodiment of the invention also incorporates novel and improved techniques for fixing to an external wall, forming the chimney as an integral part of a wall structure, joining of chimney components, internal reinforcement, and access for cleaning orforancilliaryflue pipes.

Embodiments of the invention will now be de scribed, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a part of a chimney structure according to an embodiment of the present invention, Figures 2 and 3 show alternate components which may be used in a chimney structure according to the invention, Figure 4 is a perspective view of a bracket used for securing the chimney structure against a wall, Figure 5 is a cross-sectional view showing the bracket of Figure 4 in use, Figures 6and 7are plan and cross-sectional side views respectively of a re-inforcement technique for a free-standing part of the chimney structure, Figures 8 and 9 are plan and side views respective ly of a clamp for securing together adjacent chimney components, and Figure 8A shows the clamp closed, sections forming an access aperture to the flue pipe, Figures 11 and 12 are front andcross-sectional side views respectively of a frame which may be fitted in the access aperture of Figure 10, Figures 13 and 14 respectively illustrate a cleaning door and flue pipe connector which may be fitted to the frame of Figures 11 and 12, and Figures 15 and 16 respectively illustrate perspective views of alternate components which may be used in a chimney structure according to the invention and a front view of a wall structure incorporating the components.

Referring to Figure 1, the chimney structure comprises a plurality of outer sections 10 stacked one above another and joined by cement or other suitable means. The sections 10 have a square cross-section and a rebate 11 along one outer edge.

Within the sections 10 there are centraly located a plurality of similarly stacked sectins 12 shown here as circular in cross-section although other shapes might be used. The inner sections 12 are joined together by clamps 29 to be described later, and form a flue pipe for the chimney structure. The space between the inner and outer sections is occupied by an infill material 13 to provide stability and prevent relative lateral movement of the inner and outer sections. In addition, the infill material 13 serves as an excellent insulation medium intermediate the inner and outer sections of the chimney structure. If desired, for plural chimneys each outer section 10 can comprise multiple apertures 14, Figure 2, each for accommodating a respective flue pipe 12.Furthermore, the outer and inner sections 10 and 12 respectively may be made of equal length with each inner section 12 being integrally joined to a respective section 10 by spacing webs 15, Figure 3, thereby avoiding the need for infill material 13. In this embodiment insulation is provided by an air gap intermediate the inner and outer sections.

For convenience of erection, a prefabricated chimney is often built immediately alongside an existing wall. It is essential that a chimney so located should be securely fastened to the adjoining wall and earlier chimney structures have generally lacked an adequate fastening system. The present structure incorporates a fixing system that locates both of a pair of vertically adjacent outer sections 10 while remaining unseen on the finished work. Reference is made to Figure 4 showing a fixing attachment 16 fabricated or pressed from a single piece of stainless steel or other material with similar qualities of strength and durability.

Two upward-facing members 17 are for securement to the surface of the wall 18, FigureS, and for this purpose are provided with holes 19 to accommodate proprietary masonry fixing bolts 20. A horizontal member 21 extends between the upper and lower sections 10 and a further upward-facing member 22 engages behind the inner surface of the upper section 10 and is perforated in a similar way to the members 17. Downward-facing members 23 similarly engage behind the inner surface of the lower section 10. The attachment 16 may be reversed so as to use one centrally-located fixing instead of two, using member 22 as the wall fixing point.

The rebate 11 provided in the lower edge of the upper section 10 accommodates the head of the fixing bolt or bolts 20; this rebate 11 extends over the whole of one side of the outer section 10 thus providing tolerance for the fixing in the horizontal plane.

Some part of any chimney is usually free-standing, i.e., it rises clear of the roof or adjoining walls. If this unsupported height exceeds a certain critical figure then internal reinforcement must be provided. It is essential that this reinforcement should be properly placed and supported and previous chimney structures have not included any adequate system for locating and supporting the reinforcing material.

The optimum arrangement for reinforcement in the present case consists of four vertical rods 24 located close to the corners f the outer sections 10 within the space between the inner and outer sections, Figures 6 and 7. The rods 24 are retained by bars 25 of stainless steel or equivalent material provided with holes to accept the vertical reinforcing rods 24. Two of these bars 25 are laid across the top end face 26 of any section 10 where a location point is desired and vertical support is provided by the provision of a threaded nut 27 at the upper end of each vertical reinforcing rod 24. The lower ends of the rods 24 may be retained in a similar manner two that shown for the uper ends (i.e., by bars 25 extending between vertically adjacent outer sections 10) so that the rods 24 can be placed under tension by the nuts 27.The bent portion 28 of each bar 25 is accommodated and located within the rebate 11 of the outer section 10.

The present structure incorporates a mechanical clamp 29, Figure 1, for joining the inner sections 12 which lends itself to rapid and accurate assembly.

The clamp comprises a collar 30, Figures 8 and 9, of stainless steel or similar material, and a cleat 31 of the same material. The collar 30 has an opening with out-turned ends 32 at one side for placement of the collar around the inner sections 12 across their join, and the cleat 31 is adapted to embrace the outturned ends 32. An angled bend 33 in each of the two lower corners of the ends 32 ensures that when the cleat 31 is placed in position it cannot slip downwards prior to the tightening process. The clamp 29 is tightened around the inner sections by outwardiy flattening the cleat 31 and ends 32 against the inner sections 12 with a hammer, Figure 8A. The clamp 29 is retained in position permanently by the surrounding infill 13.

It is essential for every chimney that there should be ready access for cleaning and a cleaning door needs to be provided in many cases. It is also frequently the case that a connection needs to be made between a flue pipe and the main chimney.

Previously, connections to masonry chimneys have involved laborious and wasteful cutting with a chisei. The present structure includes an assembly which includes a metal frame which will accommodate either a cleaning door or a flue pipe connection.

Referring to Figure 10, two identical precast sections 34 of the complete chimney structure fit together to provide a rectangular opening 35 from the exterior of the chimney to the interior of the flue pipe. A metal frame 36, Figures 11 and 12, is held within this opening 35 by grub screws 37 which, when tightened, bear on the side walls of the opening with surrounding gap being filled with mortar. The frame 36 is adapted to receive either a cleaning door 38, Figure 13, with internal baffle 39, Figure 12, or a flue pipe connection 40, Figure 14. It will be appreciated that the access opening to the flue pipe may also be of an elliptical or other suitable shape.

Part of a chimney is frequently formed as an integral art of a wall structure. It is important when constructing a chimney in this way to avoid the use of a continuous series of vertical joints. Masonry walls are normally built using bricks or blocks (hereinafter referred to as blocks) to an established size module and with the vertical joints staggered or bonded for increased strength.

Figures 15 shows a pair of alternately shaped outer sections 41 of a chimney structure according to the invention which can be readily incorporated in a conventional block wall 42 (Figure 16) by bonding and such that the vertical joints 43 formed with wall blocks 44 are staggered for increased strength. The outer sections 41 have a projecting portion 45 which is incorporated as an integral component of the wall 42. The outer sections 41 do not have a rebate corresponding to the rebate 11 of the chimney structure depicted in Figure 1 in this application of the invention.

A great deal of the benefit of the resent structure derives from the materials used and the proportins in which they are used. Previousiy chimneys have been constructed with the exclusive use of Portland cement which imparts good structural strength but which will not well withstand very high internal temperatures which might arise in the case of a chimney fire. Similarly, materials have been used which, in an effort to improve temperature resistance have been of a spongy nature with poor resistance to the penetration of water. The new material used in the present structure has proved on test to have a permeability factor several times less than a standard type of precast chimney.

The materials and proportions (in parts by volume except where otherwise stated) for the present structure are as follows:- Inner Section 12: 1 part high-alumina cement to BS 915 2 parts screened fines furnace or other chemicallyinert ash.

3 parts lightweight expanded clay aggregate graded to 100 per cent pass of 14mm mesh.

From 2 per cent to 3 per cent by weight of iron oxide based pigment.

In fill 13: 8 parts lightweight expanded clay aggregate as above.

1 part Portland cement.

Outer Section 10: 6 parts graded pumice.

1 part Portland cement.

From 2 per cent to 3 per cent by weight of iron oxide based pigment.

Claims (17)

1. A chimney structure comprising a plurality of pre-cast inner sections stacked one above another to form a flue pipe, a plurality of pre-cast outer sections also stacked one above another and surrounding the inner sections, and means retaining the inner and outer sections against relative lateral movement.

2. A chimney structure according to claim 1, wherein the retaining means comprises an infill material occupying the space between the inner and outer sections.

3. A chimney structure according to claim 2, wherein vertically adjacent inner sectins are joined together by a mechanical clamp encircling the inner sections across their join.

4. A chimney structure according to claim 3, wherein the clamp is formed from a collar having an oening with out-turned ends at one side for placement of the collar around the inner sections and a cleat adapted to embrace the out-turned ends, the clamp having been tightened around the inner sections by outwardly flattening the cleat and the out-turned ends of the collar against the inner sections.

5. A chimney structure according to claim 1, wherein the retaining means comprises spacing means integrally joining each inner section to a respective outer section.

6. A chimney structure according to any preceding claim, wherein the structure is erected against a wall and is secured thereto buy a bracket which extends between a pair of vertically adjacent outer sections and engages behind the inner surface of at least one of the outer sections, the bracket being secured to the wall by mechanical fixing means which project from the wall into a recessed portion of the outer surface of one of the outer sections.

7. A chimney structure according to claim 6, wherein the outer sections have a rectilinear crosssection with a rebate along one straight edge thereof, the mechanical fixing means projecting into the rebate.

8. A chimney structure according to any preceding claim, wherein a part of the structure is freestanding and is reinforced by a plurality of rods which extend substantially vertically within the space between the inner and outer sections, each rod being placed under tension by mechanical securement at its upper end to a horizontal bar which extends across the top end face of an outer section.

9. A chimney structure according to any preceding claim, wherein two vertically adjacent sections fit together to form an opening from the exterior of the structure to the interior of the flue pipe, the opening being fitted with a cleaning door or flue pipe connection.

10. A chimney structure according to claim 2, wherein the material of the inner sections comprises, in increasing proportions by volume, a high alumina cement, a chemically inert ash, and a lightweight expanded clay aggregate.

11. A chimney structure according to claim 10, wherein the material of the outer sections comprises, in increasing proportions by volume, Portland cement and graded pumice.

12. A chimney structure according to claim 10 or 11, wherein the infill material comprises, in increasing proportions by volume, Portland cement and a lightweight expanded clay aggregate.

13. A chimney structure according to any one of claims 1-5 and 8-12 when dependent on any one of claims 1-5, wherein the outer sections have a projecting portion for incorporation as an integral component of a wall and can be arranged relative to each other such that vertical joints with adjacent blocks of the wall are in staggered relationship for increased strength.

14. A chimney structure substantially as hereinbefore described with reference to Figure 1 and Figures 4 to 14 inclusive.

15. A chimney structure substantially as hereinbefore described with reference to Figure 1 and Figures 4 to 14 inclusive as modified by Figure 2 or Figure 3.

16. A chimney structure substantially as hereinbefore described with reference to Figure 1 and Figures 6 to 16 inclusive.

17. A chimney structure substantially as hereinbefore described with reference to Figure 1 and Figures 6 to 16 inclusive as modified by Figure 2 or Figure 3.