Chimney
FIELD OF THE INVENTION 
     This invention relates to a chimney, and in particular to a chimney constructed from separate chimney units, and to the chimney units therefor. 
     BACKGROUND TO THE INVENTION 
     Chimneys are used in a variety of locations, and for a variety of applications. In particular, they may be used with a solar heat collector, the chimney containing one or more turbines to generate (electrical) power from the uprushing, solar heated, air or other gas. Alternatively, they may be used for other types of power generation, or with desalination plants and/or as emission and exhaust devices. 
     Traditionally, chimneys have been constucted of brick, concrete, steel or other reinforced or substantially rigid materials. Rigid construction methods are also used. These chimneys are expensive to construct and to maintain, and, due to the difficulty of supporting the weight of the chimney, are also limited in the height to which they can be built. Additionally, the problems of wind resistance and aerodynamic stability in the event of strong lateral winds limit the height of such chimneys. 
     DESCRIPTION OF THE PRIOR ART 
     In order to facilitate easier on-site construction, it has been proposed to construct chimneys from pre-fabricated chimney sections or units. One known design is that of French patent 2,079,479, which discloses a chimney made up of standard units mounted one upon another. The units are individually rigid. 
     As a means to reduce the weight of an erected chimney, U.S. Pat. No. 3,974,756 teaches a chimney constucted from individual chimney units, wherein each of the units is of flexible lightweight material. The assembled chimney is held erected by a balloon. 
     A lightweight chimney is disclosed in German patent 280,351, wherein the chimney is inflatable. The chimney disclosed in this patent has vertical partitions dividing the chimney into separate vertical sections. 
     However, whilst these known chimney arrangements seek to offer an easily constructed and/or lightweight chimney, so that in theory a very tall chimney could be constructed, these chimneys are substantially rigid, and suffer significant resistance to lateral impacting winds. This is a recognised disadvantage for those applications, such as solar collector chimneys, which would benefit from using a very tall chimney. The substantially rigid form of known chimneys leads directly to an upper limit on the useful height of such chimneys. 
     STATEMENT OF THE INVENTION 
     It is the object of the present invention to provide a chimney which avoids or reduces the above disadvantage, and which chimney is able to withstand a lateral wind of increased force, and which may usefully be constructed to a greater height. 
     Thus, we provide a chimney formed from separate units mounted one on top of another, each unit having an upstanding wall comprising separate segments, which segments are individually movable relative to the unit so as to flex resiliently inwardly under the action of a wind force. Having flexed one or more of the wall segments inwards, the wind can flow into an erected chimney to be deflected in an upward direction, towards the open mouth of the chimney. 
     Our proposal has the advantage that the chimney can be lightweight and inflatable, reducing the construction costs greatly. Additionally, because the segmented panels are flexed inwardly under the influence of wind forces, and deflect the air into the chimney and upwards towards its open end, the chimney can withstand high lateral wind forces, and, together with its lightness, this allows a chimney to be constructed up to heights of, for example, 10,000 meters, and perhaps more. 
     Because an impacting lateral wind is deflected into the chimney, and upwards towards the open end of the chimney, the performance of the chimney in strong wind conditions is enhanced. 
     The sectional construction of this chimney from separate units facilitates rapid construction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be further described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a side sectional view of a segmented floating chimney according to the invention; 
     FIG. 2 is a plan view of one of the chimney units; 
     FIG. 3 is a partial perspective view of one of the chimney units, with some of the wall segments removed; and 
     FIG. 4 is a side sectional view of one of the chimney units in the presence of an impacting lateral wind, with some of the wall segments in an inwardly flexed position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The chimney 1 of FIG. 1 comprises a solid chimney mount 2, of concrete or other solid material, constructed at ground level. Typically, the chimney mount 2 will be apertured (not shown) to permit the entry of air into the chimney e.g. heated air from a solar collector. Additionally, the chimney mount may carry a turbine, caused to rotate by the upflowing airy and connected to an electrical generating system. 
     Located upon chimney mount 2 are three segmented chimney units 3. Mounted to the topmost chimney unit 3c is a securing ring 4; guy ropes 5 anchor the securing ring 4 to the ground, and thus prevent substantial lateral movement of the top of the chimney. Additionally, guy ropes 6 anchor the lowermost unit 3a to the ground. The guy ropes retain the chimney substantially vertical, but permit some degree of movement against strong lateral wind forces. 
     In other embodiments all of the chimney units are supported by guy ropes. Typically, the guy ropes will be of steel wire or nylon cord, though other suitable materials may be used. 
     Each of the chimney units 3 is inflatable, and has an annular tubular base 10 with a continuous lip 11 at its periphery. In use, the annular base of each unit will rest upon the unit 3 directly beneath it, and the lip 11 will surround the upstanding side wall of the lower unit, resisting lateral movement therebetween. The base 10a of the lowermost unit 3a will rest upon the chimney mount 2, and the lip 11a will surround the side wall of the mount 2. 
     As better seen in FIGS. 2 and 3, the side wall of each chimney unit comprises wall segments 12 which are independently connected to the annular base 10. The segments 12 are independently movable relative to the base 10, i.e. the material from which the chimney units are constructed, and the compressibility of the gas therein, allows the segments 12 to individually &#34;pivot&#34; adjacent their connection to the base 10. Thus, in the presence of lateral wind forces of sufficient strength, one or more of the segments may be resiliently flexed towards the central axis of the unit (FIG. 4). 
     As shown in FIG. 2, in this embodiment each segment has rounded sides, to provide substantially line contact with its adjacent segments. Also, each segment may flex towards the central axis of the unit without affecting other segments. In an alternative embodiment, the segments are wedge-like, so that in the presence of a strong impacting lateral wind, a single segment will engage its neighbours, so that several segments are caused to flex together. 
     To construct a chimney according to the invention, the segmented chimney units are inflated with hot-air, helium or hydrogen, for example, and located so that the lip 11a of the lowermost unit 3a fits around the side wall 8 of the chimney mount 2. Further segmented units are inflated and placed in position so that each unit has its lip 11 fitted closely over the side walls of the unit directly below it. The number of units used will determine the height of the chimney. 
     In an alternative embodiment, the segmented units are connected to each other by expandable connections, e.g. spring wires or elasticated ropes, so that adjacent units can move to a limited degree relative to one another, but remain substantially in place to form a continuous funnel for the chimney. 
     To permit re-inflation of the units, preferably to a specified pressure, each unit has an inflation valve inlet (not shown). These valve inlets may be connected to inflation tubes running down to ground level so that they can be inflated with hot air or other gas, pumped up from ground level. The units can be constantly or regularly re-inflated in this way, or intermittently re-inflated as and when necessary. Alternatively, they may be regularly or intermittently re-inflated from inflation units carried by a helicopter or small aircraft. 
     In an alternative embodiment, two or more inflation inlet valves may be provided for each unit, and the unit will be partitioned so that a leak from one partitioned region does not cause deflation of the entire unit. For example, the annular base may be partitioned off from the segmented side walls, and the segmented side walls may be separately partitioned into two or more separate inflation regions. This embodiment Would also permit different inflation pressures to be used in the different regions, e.g. a higher pressure might be desired in the annular base than in the wall segments. 
     The inside diameter of the floating chimney will conform to that required in the circumstances of its application, but can have a dimension in the range of from 1 meter to 1800 meters. 
     As seen in FIG. 4, the segments facing the wind flowing in a direction indicated by arrows W flex inwardly, deflecting the wind inwardly and upwardly of the chimney, towards its open exit end. 
     To avoid or reduce the possibility of wear occurring at the tip of the flexing segment and the underpart of the annular base, these parts can be locally strengthened e.g. by local thickening of the base and segment material. Alternatively, it can be arranged that the flexing segments do not touch the underpart of the adjacent annular base, the separation between adjacent units for example being maintained by non-flexing struts, of reduced cross section and offering low wind resistance. 
     In an alternative arrangement the segmented panels are suspended from adjacent upright columns. In this embodiment some or all of the panels do not need to be inflatable and inflated, or floating.