The subject of the invention is a duct fan with a gravity-mechanical system and protection against reverse thrust. The device is applicable to various ventilation systems in rooms of any size.

The solution concerns the flow of fluids, especially the air.

Various types of fans are known.

The fresh air supply ducts consist of a set of parallel tubes extending from the inlet openings in the cap plate of the outer panel, through the transverse partition in the wall outlet and the casing, towards the ends with the outlet openings in the bottom of the casing. The disadvantage of the known solutions lies in the unidirectional airflow. The solution, according to the invention, overcomes the disadvantages resulting from the prior state of the art. The fan according to the invention works both when the fan is in the on and off mode. The fan according to the invention protects against counterflow to a significant degree. The fan according to the invention protects against undesirable backflow ("backflow") better than the solutions known from the prior state of the art. Moreover, the solution according to the invention is more effective in use, more efficient and more economical.

The essence of a duct fan with a gravity-mechanical system and protection against reverse thrust lies in the system of ducts that narrow in opposite directions, sharing the partition between the ducts, the central duct having a narrow stream inlet and a wide outlet; at the outlet, a mechanically-driven fan is placed, while the central duct is provided with a check valve, preferably located at its inlet; around the central ducts, satellite ducts are located, with a wide medium inlet and a narrow outlet; the ducts share side walls.

In this solution, the mechanically-driven fan forces the streams to flow in the central duct in the desired direction. Around the central duct, satellite ducts are placed. They are adjacent, shaped in the opposite way to the central duct. If more than one duct narrowed at the inlet is used, all the ducts narrowed at the inlet have check valves to prevent the flow of the medium in the opposite direction. The central duct is located in the flow axis. Adjacent ducts are based on mechanically unforced flow and act as flow accelerators.

The solution according to the invention is presented in the attached figures 1-12, where:

Fig. 1 shows the fan module model - a flat-shaped module in a horizontal layout, with a closed check valve,

Fig. 2 shows a diagram of a fan module - a concave spherically-shape module in a horizontal layout, with an open check valve,

Fig. 3 shows a diagram of the fan module - the module in a vertical layout,

Fig. 4 shows the front view of the fan,

Fig. 5 shows the fan in a round-shaped casing in a horizontal, non-spherical layout - front view,

Fig. 6 shows the fan in a round-shaped casing in a horizontal, non-spherical layout - side view,

Fig. 7 shows the fan in a round-shaped casing in a horizontal, non-spherical layout - rear view,

Fig. 8 shows a section through a fan in a round-shaped casing in a horizontal, non-spherical layout

Fig. 9 shows a fan in a square-shaped casing in a horizontal, non-spherical layout - front view,

Fig. 10 shows a fan in a square-shaped casing in a horizontal, non-spherical layout - side view,

Fig. 11 shows a fan in a square-shaped casing in a horizontal, non-spherical layout - rear view,

Figure 12 shows a cross-section through a fan in a square-shaped casing in a horizontal, non- spherical layout

The fan with a built-in gravity and mechanical system has a casing in the shape of a circle, tetrahedron, or polyhedron. Inside the casing, in its central part, a central duct (1) is placed. This duct has a narrow stream inlet and a wide outlet. Around the central duct (1), adjacent (satellite) ducts (2) are placed, which are shaped in the opposite way, i.e., with a wide stream inlet and a narrow outlet. The central duct (1) and adjacent ducts (2) share side walls. A check valve (4) is located in the central duct (1), preferably at its narrowest point. This valve is known in the prior state of the art and preferably comes in the form of a pivoting flap fitted at the inlet to the central duct (1). On the opposite side of the central duct (1), i.e., at its widest point, at the outlet, a mechanically-driven fan (3) known from the prior state of the art is placed. In the closed position, the check valve (4) tightly fills the narrowest point of the central duct (1), i.e., the medium inlet. While changing the device's operating mode, when the check valve (4) goes into the open mode, the pivoting valve flap (4) falls into the central duct (1), i.e., towards the medium outlet, that is towards the widening duct. The flap is attached in a manner known from the prior state of the art, preferably at one point, enabling it to close the central duct (1) or open it - depending on the fan's operating mode.

The fan shaped in this way operates in two variants - with the mechanical drive on and off. When the mechanical drive is on, the stream that enters the fan through the narrow medium inflow inlet gains increasing velocity as it approaches the working fan. The ejection of the airstream behind the fan blades in the central duct accelerates the flow, also in adjacent (satellite) ducts.

When the mechanical drive is off, the fan can work in three variants: when the gravity duct generates correct pressure, when the gravity duct generates excessive pressure, and when the gravity duct generates counter pressure (overpressure), i.e., backflow. In a situation in which the duct generates correct negative pressure, the design of the central duct, due to its narrowing at the inlet, generates a non- significant airflow. The streams flowing into the fan are mainly taken over by the adjacent (satellite) ducts, which widen at the inlet. The streams flowing through these ducts, which narrow towards the outlet, gain velocity. The streams from adjacent (satellite) ducts, which are arranged distally around the central ducts, generate a negative pressure at the outlet of the central ducts, which increases the velocity (draft) of the medium flow in the central duct (even though the mechanical drive is off).

In the solutions known from the prior state of the art, when the gravity duct generates excessive negative pressure, the stream flow is too intense, which leads to an uncontrolled loss of energy. The use of the solution according to the invention in this system, i.e., alternately narrowing and widening ducts, will reduce and limit the negative pressure force in the entire device.

If the gravity duct generates counter pressure (overpressure), known as backflow, the most intense stream flow in the undesirable direction would occur in the central duct due to its longitudinal section narrowing, preferably for the receding streams. This flow, however, will be blocked by a check valve situated in the central duct. The medium flow in adjacent (satellite) ducts will be hindered by the narrowed steam inlet surface to these ducts in relation to the opposite surface.

The solution according to the invention is presented in the implementation example, which does not limit the invention:

Example 1:

The fan with a built-in gravity-mechanical system has a casing in the shape of a circle. Inside the casing, in its central part, a central duct (1) is placed. This duct has a narrow airstream inlet and a wide outlet. Around the central duct (1), adjacent ducts are arranged (2), shaped in the opposite way, i.e., with a wide air inlet and a narrow outlet. The central duct (1) and adjacent ducts (2) share side walls. In the central duct (1), at its narrowest point, a check valve (4) is placed. On the opposite side of the central duct (1), i.e., at its widest point, at the outlet, a mechanically-driven fan (3) is placed. In the closed mode, the check valve (4) tightly fills the narrowest place of the central duct (1), i.e., the air inlet. In this position of the check valve (4), air streams (5) in the central duct (1) flow in the undesirable direction, i.e., from the mechanical drive (3), which is in the off mode, to the check valve (4) where it faces resistance. In the adjacent ducts (2), air streams (5) flow in the opposite direction than in the central duct (1).

Example 2:

The fan with the built-in gravity-mechanical system is equipped with a casing in a tetrahedronshaped cross-section. Inside the casing, in its central part, a central duct is placed (1). This duct has a narrow medium inlet and a wide outlet. Around the central duct (1), adjacent ducts are placed (2) shaped in the opposite way, i.e., with a wide air inlet and a narrow outlet. The central duct (1) and adjacent ducts (2) share side walls. In the central duct (1), at its narrowest point, a pivoting flap which serves as a check valve (4), is placed. On the opposite side of the central duct (1), i.e., at its widest point, at the outlet, a mechanically-driven fan (3) is placed. The pivoting valve flap (4) falls into the central duct (1), i.e., towards the medium outlet; then, the check valve (4) works in open mode.

In this position of the check valve (4), both in the central duct (1) and in the adjacent ducts (2), the medium (5) flows in the desired direction, i.e., from the open inlet of the central duct (1) to the mechanical drive (3) which is activated. Example 3:

The fan with the built-in gravity-mechanical system is provided with a casing in the shape of a polyhedron. Inside the casing, in its central part, a central duct is located (1). The duct has a narrow stream inlet and a wide outlet. Around the central duct (1), adjacent (satellite) ducts are arranged (2), which are shaped in the opposite way, i.e., with a wide medium inlet and a narrow outlet. The central duct (1) and adjacent ducts (2) share side walls. A check valve (4) is placed in the central duct (1), next to the fan blades. This valve is known in the prior state of the art. At the widest point of the central duct (1), at the outlet, a mechanically driven fan (3), known from the prior state of the art, is located.