Current conditions At the present time, a special attention is paid to environment-friendly technologies, so any uneconomical and imperfect fuel burning, resulting in high fuel consumption, low caloric usability and consequent extremely high air pollution means a significant problem. To eliminate or at least reduce the unfavourable state either chimney extensions with a roof or extended chimney tubes are used, ended with a rotary cover with a fixed helm. The extended chimney tube increases the draft, lengthening the chimney line. Air flow sets the rotary cover in such a position that prevents from air flow coming in the chimney from above, protects the chimney against direct sunshine, and partially protects the interior of the chimney against rainwater. There is an advantage, however: the rotary cover becomes sooted after some time, and then its easy rotation is not easy any more, and frequent maintenance is required. In case of conditions of low draft, the chimney extension is not able to increase the draft effectiveness; what is more, the extension erodes by the effect of flue gas. There are chimney extensions, e. g. those based on the Czech patent CZ 230019 and CZ 235490. They consist of an extended vertical chimney tube, connected with a horizontal or bevelled tube, provided with short vertical tubes at both ends. To provide good draft, only air ejection on the edges of the short vertical tubes is used, or the ends of the tubes are provided with an additional blade. This solution more effective, however, much more complicated. Lastly, there is also a modular chimney head based on the Czech patent CZ 163547. It is based on a set of several rotary rings situated one above another and curved upwards, and of ribs that divide the space between the rings in several channels of gradually narrowing cross section. The head suction effect follows from catching and directing the air flow in the narrow channels, formed by the curved-upwards rings and radial ribs. The basic disadvantage of this system is a constant distance between the individual rings, not taking into account the characteristics of the burning process of each particular combustion device and their specific need of flue gas venting.

The concept of the technical solution The above mentioned disadvantages may be eliminated if the chimney head is used of the above mentioned type, consisting of the ring and the chimney insert, which is a really favourable technical solution. The ring is made in the shape of a fixed spoiler A, on which another ring, shaped as a spoiler B, is hung by means of at least two staybolts, ended in bearing nuts; it is possible to modify the distance between the spoiler B and the fixed spoiler A.

It is good to install staybolts in the spoiler A, while the bearing nuts are placed in the spoiler B.

A hoop should be put between the A and B spoilers (by means of fixing consoles, installed on the staybolts. The distance between the hoop and the spoiler A should be limited by upper distance tubes and stabilized with a locking element.

It is advisable to provide the fixing consoles with a screen with a removable cover.

In order to construct a really well-working system, another fixed ring (spoiler C) should be placed between the hoop and the spoiler B; the spoiler C should be installed on staybolts as well, and its distance from the fixing consoles should be limited by lower distance tubes. Axial stabilization should be provided by means of a locking element.

It is advisable to align all three spoilers A, B, C. The ring spoilers A, B, C should be conical, narrowing upwards.

The spoiler B should be provided with struts.

The chimney insert should be connected to the spoiler B.

Another advantages of this technical solution are the simplicity of the construction, easy manufacture, top reliability based especially on increased efficiency of combustion devices, and the combustion process quality; in addition, elimination of influence by side wind is provided, in the scope of-75° through +75° of the wind starting blow by directing it to the chimney draft regulator, both emission volume and soot volume are reduced; reverse movement of flue gas is eliminated, chimney lifespan is longer, heat loss is lower, excessive cooling of combustion devices is eliminated, combustion temperature is higher, along with safe and easy operation.

Illustrations Fig. 1 shows a schematic half-section of a sample chimney head with two spoilers A, B. Fig. 2 shows a schematic half-section of a sample chimney head with three spoilers A, B, C.

Example of the technical solution The chimney head shown in Fig. 1 consists of a ring, spoiler A 1. The spoiler A 1 is provided with built-in staybolts 4, whose heads 41 stick out of the spoiler A 1 and are shaped as-for example-wings 411. The heads 41 and the staybolts 4 may also hexagonal or ended as a cylinder with hexagonal interior, etc. (not shown in the picture). The shanks 42, staybolts 4 are connected with fixing consoles 91 provided with a hoop 9. The fixing consoles 91 are provided with a screen 8 with a removable cover 81, which is put on staybolts 4 as well. The distance between the spoiler A 1 and the screen 8 is limited by upper distance tubes 6, put on shanks 42, staybolts 4. They are blocked against axial shift of the fixing consoles 91 with a locking element 5, e. g. with a cotter or a safety ring, situated on the shanks 42, staybolts 4, under the bottom side of the fixing consoles 91. The shanks 42, staybolts 4, are provided with another ring, spoiler B 2, which is put on the shanks 42, staybolts 4 and fixed by means of bearing nuts 21 (with outer and inner thread).

The bearing nuts 21 bear the shanks 42, staybolts 4, while the outside thread of the bearing nuts 21 is provided with a clamping nut 22, in order to stabilize not only the spoiler B 2, but the struts 101 and the chimney insert 10 (which may be conical or cylindrical or prismatic (not shown in the picture). The arrangement of the chimney in Fig. 2 is similar: the difference is one more (at least one) ring, spoiler C 3, situated between the fixing consoles 91 and the spoiler B 2. The spoiler C is put on shanks 42, staybolts 4, as well, while the distance between the bottom side of the fixing consoles 91 is limited by bottom distance tubes 7, directly leaned against the bottom side of the fixing consoles 91. In this case, the blockage by the locking element 5 is not required since the stabilization of the individual parts of the chimney head is provided by the upper distance tubes 6, bottom distance tubes 7 and the locking element 5', i. e. cotter or safety ring, etc. All three spoilers A, B and C are conical, narrowing upwards, and they are aligned. They are made of metal sheet, especially steel, better stainless.

The manipulation with the chimney head is shown in Fig. 2. The chimney head is inserted in the chimney (not shown in the picture) and anchored in such a way that the chimney insert 10, connected with the spoiler B 2, corresponds to the profile of the chimney intake at base, and the struts 101 are in touch with its surface. Regulation of the chimney draft and suction effect is made by turning (by hands or by a stepper motor (not shown in the picture), staybolts 4, using the wings 411. First, the distance between the spoiler B 2 and the spoiler C 3 is decreased to its minimum. Thus the volume of the air flow lowered, the combustion process is reduced, and the smoke starts leaving the heating device (not shown in the picture), spreading directly in the surrounding environment. After that, optimal combustion may be set, by reverse turn of the limit bolts 4, until the gap between the spoiler B 2 and the spoiler C 3 is big enough to increase the flow of the air in such a way that the smoke is drawn directly into the chimney and does not spread into the environment any more. If you need to clean the chimney intake at base, you only remove the cover 81, screen 8.

Serviceabilitv in industry The chimney head designed according to this technical solution may be perfectly used not only for better taking the flue gas away at burning process with heating systems using various fuels, but also to improve efficiency of ventilation systems.

LIST OF RELATIONAL SYMBOLS 1 Spoiler A 2 Spoiler B 21 Bearing nuts 22 clamping nut 3 Spoiler C 4 Staybolts 41 staybolt heads 411 wings 42 staybolt shanks 5, 5'locking element 6 Upper distance tube 7 Bottom distance tube 8 Screen 81 Removable cover 9 Hoop 91 Fixing consoles 10 Chimney insert 101 Strut