The present invention refers to a throttling device for flow rate control of a fluid, and of the kind that comprises a flow channel having an essentially circular cross-section and a reducible throttle means arranged at its flow through section by means of an actuation means, whose flow through section by means of an adjustment means can be reduced and increased respectively, and which throttle means consist of a surface element arranged in the flow channel and attached to it, which by means of the adjustment means is formable from essentially cylindric to semi-conical form.

BACKGROUND OF THE INVENTION

The most common throttling of an air flow in a ventilation channel is by means of a throttle, which from the outside of the channel can be adjusted to a right throttle position. The drawback of this type of throttling is that a turbulence is produced and the sound level is practically unacceptable. There are also throttling devices on the market now, which functionally are constructed as iris diaphragm with a plan, radially provided iris plates, n which some sound level has been reduced compared with a turnable throttle, but these are much more expensive to manufacture. A further improvement has been achieved through an iris diaphragm variant, where the iris plates form a variable, frustum of a cone. Structural design of this embodiment is more complicated and thereby it has higher costs of production. Further, it is common for all these throttling devices that they considerably complicate the cleaning of the channels.

Through EP 0334 519 A2 and GB 2 095 793 A are throttle ventils known, whose throttle means consists of a flexible cylindric sleeve, whose ends are attached to channel portions or rings which are turnable relative each other. By turning these, the middle or end sections of the sleeve are wired together and a larger or smaller opening is provided. The sleeve can be made of

a needled product up to the half having closed meshes and half a synthetic plastic material.

These throttle ventils are difficult or impossible to clean and do not endure mechanical cleaning apparatus. The strength of the flexible sleeve against the flowing medium is poor, especially, if it contains solid particles. Another drawback is appearance of unwanted sound phenomenon and creation of turbulence through the folds of the constricted sockets.

THE OBJECT AND THE MOST IMPORTANT FEATURES

The object of the invention is to provide a throttling device, which has simple structural design and thereby cheap to manufacture, which do not throttle the laminar air flow, i.e. do not produce turbulence around the throttle means, has lower sound level than any other throttling device on the market, which with a simple operation can be mounted in existing channels, alternatively, it can be sold preassembled as short connection pipes and do not prevent the cleaning of the channel.

These tasks, according to the invention, have been solved by the surface element consisting of a rigid, flexible, preferably essentially square thin material, e.g. a thin sheet metal, plastic plate or the like, which is formable to a cylinder opening in longitudinal direction, whose first end portion is attached to or movably pivoted in the flow channel or similar, and whose opposite free end portion through overlapping of the cylinder walls is reducibly forming a cornet with both ends open.

DESCRIPTION OF THE DRAWINGS

The invention will be described closer through some embodiments with reference to the enclosed drawings.

Fig. 1 shows a cross-section along line I-I in fig. 2, through the throttling device according to the invention, substantially,

in its unthrottled position.

Fig. 2 shows a bottom view of the throttling device according to fig. 1 seen from the inlet opening.

Fig. 3 shows a view of the throttling device analogous to fig. 1, with the throttle means in throttled position.

Fig. 4 shows a bottom view of the throttling device according to fig. 3 seen from the inlet opening.

Fig. 5 shows a bottom view of the throttling device according to fig. 3 seen from the outlet opening. Fig. 6 shows the throttle means as a sheet material, in a frontal view.

Fig. 7 shows, in an enlarged scale, a cut through the end portion of the throttling device according to fig. 1, completed with a guide sleeve. Figs. 8 and 9 show lateral views of the throttling device with adjustment means in two different designs.

DESCRIPTION OF THE EMBODIMENT

The throttling device, on the drawings designated with 10, according to figs 1 - 5 consists of a tubular flow channel 11, preferably at both ends provided with a joining means 12, for connection to a ventilation channel or the like. Inside the flow channel 11 a throttle means 13 is provided, which consist of a surface element 14, which in its extended, original state, is in form of an essentially rectangular, thin material, e.g. a thin sheet metall, a plastic sheet, flexible plastic plate or the like which from the rectangular shape has obtained the form illustrated in fig. 6. As the throttle means, the surface element has substantially the cylindric shape as shown in fig. 1 and bears on the inside of the flow channels. On the surface of the channel an adjustment means 15 is attached, which by means of a flexible device 16, e.g. a cord, wire, thread or similar is connected to the throttle means 13 in such a way that it can be formed from its cylindrical shape, according to fig. 1, to a corr -, open at both ends, substantially forming a frustum of a con- according to fig. 3. The "rectangular" surface element 14

is at the long side, which forms the base of the cone, i.e. the admitting end of the throttling device, at the corner sections 17 and 18 provided with the hole 19. In the shaped form of the surface element as a throttle means in the flow channel, the corner sections overlap each other, so that the holes 19 are arranged in front of each other and positioned by means of a support shaft 20 to the flow channel 11. At the opposite end of the surface element, i.e. the discharge end of the throttling device, at a corner section 21 a third hole 22 is arranged as a holder for said flexible organ 16.

To facilitate the formation of the throttle means 13 from the cylindric form to cornet form and vice versa, the corner section 17 is provided with a lug 23 connected to one short side 24 of the surface element. Further, the corner sections 17 and 18 blend smoothly to a arch 25 in one long side 26 of the surface element, whereby a good, almost a tight connection of the base end of the cone to the inside of the channel is provided. Further, the second short side 27, in the direction of the second corner section 18 to the forth corner section 30 is cut obliquely, to facilitate the adjustment of the throttle means in the throttled position. The third corner section 21 of the surface element is equipped with a bias 28, which partly transit into the second long side 29 of the surface element and partly in the short side 24. The object of this bias is to reduce the friction against the channel, but also to prevent the corner jamming on the channel wall.

The adjustment means 15, shown in connection with the embodiment according to the figures 1 - 5, besides the flexible means 16 includes an adjustment device 35 arranged on the surface of the flow channel, consisting of a lever 33 mounted about a screw 32 on an angel support 31, at one short arm of which one end of the flexible means 16 is attached. The longer arm of the lever 33 can manually be swung and locked in different angel positions by means of a wing nut 34 or the like screwed onto the screw 32. A dial on the angel support 31 allows a precise adjustment of the

throttle degree of the throttle means.

To obtain disturbance free flowing through, from flow point of view, through the channel it may be preferred that in the transition between the channel 10 and the throttle means 13 to arrange a guide sleeve 36, fitting to the inside of the flow channel and at the inlet side equipped with a bevel 37. At the opposite end portion, the guide sleeve 36 is arranged with an outer peripheral, conically slightly tapering shelf 37, which between the channel and the sleeve forms an annular space 38, in which the base portion of the cylindrical and conical throttle means 13 respectively together with support shaft 20 may be accommodated. Since, in the embodiment shown in figs 1 - 7 changing the form of the cornet from the cylindrical to conical form occurs eccentrically, i.e. the forming occurs with starting point from the fixed support shaft in the direction towards the opposite channel inner wall, along which the cornet is essentially parallel, in the guide sleeves outlet end busy a parabola shaped cutting 39 is arranged, whose highest point on the parabola is in alignment with the support shaft 20. If the surface element is formed with a great precision, according to the topic of fig. 6 and concerning the inner diameter of the flow pipe, such a reliable bearing of the base portion of the throttle means and its end edge respectively on the inside of the channel will be obtained that the guide sleeve will be unnecessary.

Fig. 8 shows an embodiment of the adjustment means 15, in which the flexible means has been replaced by a locking screw 41 connected to a corner section 21 of the throttle means 13 and extending through a slit 40 in the channel, which by means of a nut 42 can by positioned in the slit.

A third embodiment of the adjustment means 15 is shown in figure 9, which is a combination of a flexible means 16 and at least one adjustment screw 43, which partly, with its free end, may be brought to press on the outlet portion of the throttle means and partly wire round its screw shaft the flexible means, so that a

reduction of the outlet end of the cornet is obtained. By loosening the screw and at the same time wiring up the flexible means from the screw shaft the cornet is opened. In this embodiment the throttle means 13 can be placed in the centre of the flow channel, by arranging several, e.g. three, adjusting screws 43 distributed along the periphery of the channel.

The invention is not limited to the shown and the described embodiments, but can be varied within the scoop of the claims. Consequently, the throttling device can be used for other applications than the ones described and the medium to be throttled can be gaseous fluids, just as well as floating or a mixture of these.

Designation numeral

10 throttling device

11 flow channel 12 joining means

13 throttle means

14 surface element

15 adjustment means

16 flexible organ 17 first corner section

18 second corner section

19 support hole

20 support shaft

21 third corner section 22 hole

23 lug

24 first short side

25 soft arch

26 first long side 27 second short side

28 bias

29 second long side

30 forth corner section

31 angel support 32 screw

33 lever

34 wing nut

35 adjustment device

36 guide sleeve 37 shelf

38 annular space

39 cutting

40 slit

41 locking screw 42 nut

43 adjustment screw