WO1995005565A1

WO1995005565A1 - Silent regulating valve

Info

Publication number: WO1995005565A1
Application number: PCT/SE1994/000739
Authority: WO
Inventors: Berit Persson
Original assignee: Bröderna Rasch Ab
Priority date: 1993-08-13
Filing date: 1994-08-12
Publication date: 1995-02-23
Also published as: SE9302637L; SE9302637D0; SE509014C2

Abstract

A control valve (2) for installation in ventilation duct systems (1), comprising first and second tubular sections (2a; 2b), and a body (2c) which can be moved axially therewithin. In order to achieve maximum sound absorption, the mutually facing surfaces of the second tubular section (2b) and the body (2c) define therebetween an acute angle (a), preferably an angle of about 15°. The body (2c) has a perforated downstream end (2c1), wherein the extent of the perforations corresponds to roughly 40 % of the area of said end. The cavity of the body (2c) is filled with sound-absorbent material (5), preferably mineral wool.

Description

SILENT REGULATING VALVE

TECHNICAL FIELD

The present invention relates to a control valve which is intended for incorporation in a ventilation duct system and which functions to generate conditions whereby essentially similar ventilation is achieved in the various branches of the duct system.

BACKGROUND ART

A ventilation system which lacks such a control valve would result in a low degree of ventilation with regard to those consumers that are most remote in the system, or the system would fail to provide any form of ventilation whatsoever. The extent of the ventilation desired, i.e. the distribution of ventilation air, is achieved conventionally with the use of butterfly valves or like valves.

One drawback with butterfly valves is that they generate turbulence and therewith unpleasant noise which propagates through the ventilation ducts. Acoustic silencers or sound traps have been mounted adjacent the butterfly valves in an attempt to minimize the occurrence of unpleasant noise. This has resulted in a considerable increase in the space required for installation.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a control valve of the kind defined in the introduction which will generate much less noise than would otherwise be generated at equal air quantities and pressure drops, and which has a relatively short inbuilt length. This object is achieved with a valve which includes a first tubular section which has a cross-sectional area that is larger than the cross-sectional area of the channel system in general, and which further includes a second tubular section which is located downstream of the first tubular section and whose cross-sectional area decreases successively from the cross-sectional area of the first tubular section to the cross-sectional area of said duct system, and the length of which is such as to form an acute angle between the second tubular section and a body which can be moved axially in the valve. In order to achieve optimal flow conditions, the acute angle between the second tubular section and the axially displaceable body has a value of about 15°. It is also beneficial to provide the axially movable body with a cross-sectional area which has in general the same size as the cross-sectional area of the duct system, and to give said body a length which is generally equal to the length of the second tubular section. The body is conveniently displaced in the valve by a transmission means that can be activated from outside the valve. The axially displaceable body is advantageously filled with a sound-absorbent material, for instance mineral wool, with the intention of further reducing the generation of sound in the valve. The valve will preferably have a circular cross-sectional shape and is preferably made of steel plate, wherein the downstream end of the axially movable body may consist in perforated metal sheet. The extent of the perforations may correspond to roughly 40% of the area of said plate.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will now be described in more detail with reference to a preferred exemplifying embodiment thereof and also with reference to the accompanying drawing, in which

Fig. 1 is a schematic longitudinal sectional view of a valve constructed in accordance with the present invention;

Fig. 2a is a cross-sectional view of the valve shown in

Fig. 1; and

Fig. 2b is an enlarged part view of transmission means shown in Fig. 2a and functioning to displace a body axially in the valve from outside the valve.

In Fig. 1, the reference numeral 1 identifies a short section of a ventilation duct system which includes an inventive control valve, generally referenced 2. The control valve includes two tubular sections 2a and 2b and a body 2c which can move axially in said sections. The cross-sectional area of the tubular section 2a is larger than the cross-sectional area of the duct system 1. The tubular section 2b connects with the tubular section 1 and the cross-sectional area of the downstream end of the section 2b matches the cross-sectional area of the duct system 1. The length 1 of the tubular section 2b is chosen with respect to the cross-section at its respective ends such as to form an acute angle a with the longitudinal axis of the valve. The angle a will preferably be about 15°. The reason for this will be described in more detail below.

The body 2 which is displaceable axially in the valve 2 is filled with a sound-absorbent material 5, such as mineral wool, and is connected operatively with a transmission means 3 through which the axial position of the body 2c in the valve 2 can be adjusted from outside the valve. The body 2c has generally the same cross-sectional area as the duct system 1 and its length is generally equal to the length 1 of the second tubular section 2b.

Located between the wall of the tubular section 2b and the body 2c is an annular gap 4 which has a decreasing throughflow area and which thus causes a decrease in the flow through the valve 2 when the body 2c is displaced axially towards the narrower end of the tubular section 2b, and conversely increases the flow when the body 2c is displaced in the opposite direction. The angle between the surfaces on the tubular section 2b and the body 2c will be as close as possible to 15°. This is because the air is forced to accelerate as it passes through the valve, therewith generating the minimum of turbulence. This also means that sound generation will be maintained at a low level. Any other angular value will result in higher sound generation. Fig. 2b illustrates a preferred embodiment in which the transmission means 3 includes a C-shaped profile bar 3a to which the body 2c is fixed and which is slidable along a profile bar 3b which fills essentially the internal space of the C-shaped profile bar 3a and is fixed to the wall of the tubular section 2a. A toothed wheel 3d, or pinion, is rotatably mounted on a shaft 3c which extends generally radially in relation to the valve 2. The pinion wheel is mounted in the profile bar 3b and engages notches or recesses 3al provided in one leg of the C-shaped profile bar 3a, such as to enable the body 2c to be moved axially by rotating the shaft 3c with the aid of a knob (not shown) and therewith throttle or increase the air flow through the valve 2.

The inventive control valve is preferably manufactured from an imperforate material, preferably steel plate. The two tubular sections 2a, 2b of the valve 2 will thus form a sheet metal casing in whose chamber the axially displaceable body 2c is mounted. The body 2c is also manufactured from the same material and will advantageously have a perforated end-wall 2c1 placed in the downstream direction. The extent to which the end-wall 2c1 is perforated will correspond approximately to 40% of the area of said wall. The interior of the body 2c is advantageously filled with mineral wool 5, with the intention of further decreasing sound generation.

Although the inventive valve has been described and illustrated with reference to an embodiment which is preferred at present, it will be understood that this embodiment can be modified in different ways without departing from the inventive concept. For instance, the angle a can be obtained by equivalent construction of the body 2c and the second tubular section 2b, wherein the body 2c will have the form of a truncated cone and the tubular section 2b will have the form of a collar which successively closes a gap 4. In this case, as the body 2c is moved, it will extend into the downstream part of the duct system 1 to a lesser or greater extent. The extent to which the body 2c is filled with sound-absorbent material and the type of material used can also vary. Naturally, other forms of transmission 3 can be applied with the inventive control valve 2. The present invention is therefore not restricted to the aforedescribed and illustrated embodiment thereof since modifications and changes can be made within the scope of the invention as defined in the following Claim 1.

Claims

1. A control valve (2) for installation in a ventilation duct system (1) in order to provide conditions for essentially equal ventilation in the various branches of the duct system, characterized by a first tubular section (2a) which has a cross-sectional area that is larger than the cross-sectional area of the duct system (1), a second tubular section (2b) which is located downstream of the first tubular section (2a) and the cross-sectional area of which transforms successively from the cross-sectional area of the first tubular section (2a) to the cross-sectional area of the duct system (1), and the length (1) of which is such as to form an acute angle (a) between the second tubular section (2b) and a body (2c) which can be moved axially in the valve (2).

2. A valve according to Claim 1, characterized in that the axially displaceable body (2c) has essentially the same crosssectional area as the cross-sectional area of the duct system (1) and a length (1) which is essentially equal to the length of the second tubular section (2b).

3. A valve according to Claim 1 or 2, characterized by transmission means (3) which can be activated from outside the valve (2) for moving the displaceable body (2c) axially in said valve.

4. A valve according to any one of the preceding Claims, characterized in that the acute angle (a) defined between the second tubular section (2b) and the displaceable body (2c) is about 15°.

5. A valve according to any one of the preceding Claims, characterized in that the displaceable body (2c) is comprised of a hollow cylinder whose interior is filled with soundabsorbent material (5), for instance mineral wool.

6. A valve according to Claim 5, characterized in that the downstream end of the displaceable body (2c) includes a perforated end plate (2cl).

7. A valve according to Claim 6, characterized in that the end plate (2cl) is perforated to an extent corresponding to approximately 40% of the plate area.

8. A valve according to any one of the preceding Claims, characterized in that the valve (2) has a generally circular cross-section and is made of sheet metal material.