A baffel for sound absorbers

Abstract

 A baffle for sound absorbers intended for rectangular ventilation ducts. The baffle (10) has a rectangular shape when seen sideways on and also when seen in vertical cross-section transversely to the longitudinal direction and includes sound absorbing insulating material (20, 21) supported by a frame structure or casing (14, 15). The baffle is characterised in that it includes at least two juxtaposed, generally parallelepipedic baffle-parts (16) which are mutually spaced at least at one end thereof and which contain sound absorbing insulating material (20) and said insulation-material supporting frame structure or casing (14, 15). There is provided at each outer end of the baffle (10) a respective vertically extending edge-piece (12 and 13) which connect and hold together said baffle-parts (16). At least one edge-piece (12) at the outer end of the baffle (10) which meets the ventilation air has an air-flow deflecting shape. The baffle-parts (16) can be given a predetermined position in relation to one another, by appropriate selection of the edge-pieces (12), so as to form spaces (17) between two mutually adjacent baffle-parts (16). The baffle-parts (16) are conveniently disposed obliquely in relation to one another, so that the baffle (10) will be thickest at that end which is to be positioned to meet the air flow in the ventilation duct. At least one space (17) between the baffle-parts (16) shall be filled with an appropriate material (21).

Description

[0001] The present invention relates to a baffle for sound absorbers or sound attenuators that are intended for rectangular ventilation ducts. The baffle has a rectangular configuration, both when seen sideways on and when seen in vertical cross-section transversely to its longitudinal axis, and includes sound attenuating insulation material and a frame structure which supports said insulation material.

[0002] Sound absorbers intended for rectangular ventilation ducts are known to the art and are commercially available in several different forms. One such sound absorber is the so-called Multidämparen® described in our catalogue under designation PZGa. A common feature of these known sound absorbers is that they function to prevent sound generated by a fan or blower system from propagating into associated ventilation systems, to the greatest possible extent. The sound absorbers are therefore placed close to the fan system and connect with the rectangular duct of the ventilation system departing from the fans. These sound absorbers include a plurality of sound-attenuating baffles disposed in the longitudinal direction of the sound absorber, said longitudinal direction being the same as the longitudinal direction of the ventilation duct and therewith the same as the direction in which ventilation air flows, said ventilation air thus flowing transversely through the absorber in its longitudinal direction. Prior publications DE-A-2513946, DE-A-3317273, DE-A-3425450, DE-U-9406628, DE-U-29618736, EP-A-0511149 and US-A-3511336 describe different forms of sound absorbers and baffles of the aforesaid kind.

[0003] One requirement of sound absorbers of the aforedescribed kind is that they shall not cause an excessively large drop in pressure to occur in the flow direction. Consequently, the majority of known sound absorbers are designed to minimise such pressure drops. For instance, a low pressure drop will enable

• the space required for the absorber to be reduced, because a smaller absorber can be used;
• the pressure set-up in the fan system can be reduced with the same fan size;
• self-induced sound in the system to be reduced with lower air flow-rates and lower pressure set-ups; and
• the absorber can be adapted more readily to the adjacent duct system.

[0004] The pressure drop can be reduced by tapering the sound absorbing baffles in the longitudinal direction of the absorber, by which is meant that the baffles taper partially in the direction of air flow or at least have a smaller thickness at that end of the baffle which lies distal from the absorber air inlet. However, the manufacture of tapering baffles has been found both complicated and expensive in practice and consequently it has been preferred to manufacture the baffles in two parallelepipedic parts of mutually different thicknesses, these parts then being assembled so that the "distal" part will be narrower than the "proximal" part. This has naturally resulted in a greater pressure drop than that obtained with baffles that lack such discontinuities in thickness and cannot therefore be minimised to the extent desired.

[0005] Another problem with respect to the construction of such baffles is that in order to obtain an optimum sound attenuating function, their thicknesses will preferably be adapted to the width dimension of the sound absorber, the number of baffles included therein, the acoustic properties of the insulating material, and so on. This means that a wide assortment of baffle-types of mutually different widths and properties must be provided for the known sound absorbers, so as to meet all conceivable applications.

[0006] An object of the present invention is to provide a baffle for sound absorbers of the kind described in the introduction with which the aforesaid problems associated with known baffles have been eliminated at least essentially and which also provides a flexibility that, e.g., enables different baffle widths to be provided without adding to costs and enabling one and which can be readily adapted for current and/or local tapering requirements.

[0007] This object is achieved with an inventive baffle having the features apparent from the associated Claims. The baffle has a rectangular shape both when seen sideways on and when seen in a vertical cross-section transversely to the longitudinal direction, and includes sound-absorbing or sound-attenuating insulating material accommodated in a supporting frame structure. The baffle includes at least two juxtaposed baffle-parts which are mutually spaced apart at least at one end. Each such baffle-part has a generally parallelepipedic shape and includes sound-absorbing material, and a frame structure or casing that surrounds and supports this material. The baffle-parts are connected at each outer end of the baffle to vertical edge-pieces, which also function to hold the baffle-parts together. At least the edge-piece located at the baffle end that meets the ventilation air has an air deflecting shape, preferably a curved shape. The baffle-parts are given a predetermined position in relation to one another by virtue of the width of the edge-pieces, so that spaces are formed between two adjacent baffle-parts in the form of interspaces within the baffle. The width of the edge-pieces may be chosen to correspond to each predetermined baffle-width, in principle fully independent of the width of the separate baffle-parts.

[0008] According to the invention, baffle-parts may be disposed parallel with one another in the baffle if so desired. However, the baffle-parts are preferably arranged obliquely in relation to each other, so that the baffle will obtain a tapering, this form being favourable with respect to the pressure drop in the duct, as indicated in the introduction. In such cases, the baffle will thus be thickest at that end which shall be positioned to meet the air flow in the ventilation duct. Thus, there is formed between the baffle-parts a space or gap which may be of uniform width or which may narrow, depending on the angle defined by said parts with respect to each other. Although this space may be empty, it is preferred in the majority of cases to fill the space with an appropriate material and then preferably a sound absorbing material which may be of the same type as the material in the baffle-part although said material may, of course, be comprised of other material whether sound absorbing or not, so as to impart different, predetermined properties to the baffle. Thus, the baffle can be given a sound attenuating nature that varies greatly even with unchanged dimensions and configuration of the baffle-parts from which the baffle is constructed, and the baffle itself.

[0009] The edge-piece located at the forward end of the baffle, by which is meant the end that meets the air flow, hereinafter referred to as the front end-piece, is preferably curved and given a spring function with respect to the baffle-parts. The edge-piece may form a part of the frame structure or casing of said baffle-parts. Alternatively, the edge-piece may be a separate component and joined to said baffle-parts in some suitable way. The baffle can thus be given a varying taper and therewith cause a reduction in pressure drop, since the baffle-parts and their sound absorbing material can be arranged at different angles to one another right up to the point at which they engage one another at the distal end of the baffle, this being made possible by virtue of the resilient or springy end-piece. The rear edge-piece is suitably a replaceable U-shaped beam element whose width determines the rear thickness of the baffle. Thus, each baffle can be comprised of baffle-parts of standard thickness if so desired, while still obtaining a given width determined by the width of the edge-pieces.

[0010] Each baffle-part thus comprises a sound absorbing material in parallelepipedic shape and has a frame structure or casing that supports and/or holds said material together. A baffle can be constructed in many different known ways, and that type of baffle taught by the aforesaid prior documents can, of course, also be used in the construction of the baffle-parts of the inventive baffle, provided that they can be connected by the uniting end-pieces in accordance with the invention. It is preferred, however, to use U-shaped beam elements at the top and bottom of each baffle-part with a sheet of sound absorbing material placed vertically between said beams. In order to provide stability to respective baffle-parts, the top and bottom beam elements can be connected at one or both ends, this connection being achieved with the edge-pieces as indicated above.

[0011] The sound absorbing material in the baffle-parts is preferably mineral wool, and is suitably covered with glass-fibre cloth at least on those sides which face towards the air flow.

[0012] The baffle may either have a height that is adapted to the duct-dimensions concerned, or may have a smaller height which will enable several baffles to be superimposed in the duct in question. In this regard, said baffle-height may be an even multiple of the duct-height.

[0013] The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 illustrates in perspective an inventive baffle according to a preferred embodiment; Figure 2 is a perspective view of the same baffle, although the insulating sheets have been excluded for the sake of illustration; Figure 3 shows a baffle from above; and Figure 4 is a sectioned view of the baffle taken through the line A-A in Figure 3.

[0014] Figure 1 shows a baffle 10 that includes two baffle-parts 16 which each comprise a frame structure 11, a front edge-piece 12 having a curved, air-deflecting surface arranged in the front part of the baffle, and a rear edge-piece 13 having a flat surface arranged in the rear part of the baffle. The frame structure 11 includes two upper beam elements 14 and two lower beam elements 15 of U-shaped cross-section. The top and bottom beam elements belong in pairs. The baffle 10 thus has two baffle-parts 16, of which respective side surfaces that face towards the air flow can be seen in Figure 3. The side surfaces 23 of respective outer baffle-parts 16 of the baffle 10 are at least partially permeable to air. The baffle 10 is placed with its longitudinal axis along the path of the air flow in a ventilation duct, and in the majority of cases a plurality of such baffles are placed in mutually parallel and spaced relationship in the duct, so as to form ventilation air ducts between two adjacent baffles 10 or between a duct wall and an adjacent baffle. In its assembled state in a sound absorber for a ventilation duct, the baffle 10 is placed so that its front end-piece 12 will meet and deflect the air flowing in the ventilation duct. A space or gap 17 is provided inside the baffle 10 between the two baffle-parts 16.

[0015] Although the illustrated interspace has an essentially uniform cross-dimension, it will normally taper towards the far end of the baffle 10.

[0016] Figure 2 is a perspective view of the same baffle 10 as that shown in Figure 1, with the exception that the insulating material has been omitted so that the whole of the frame structure 11 can be seen. The frame structure 11 includes two mutually spaced upper U-shaped beam elements 14a,b and corresponding bottom U-shaped beam elements 15a,b. The front end-piece 12 will conveniently be resilient or springy such as to enable the respective beam-element pairs 14, 15a and 14, 15b of each baffle-part 16 to be turned towards each other so as to obtain a predetermined distance between the distal ends of the element pairs and so that said element pairs will also define a given angle therebetween. The frame structure may include at both the front and the distal end of the baffle, vertical posts 18 that are connected with and bind together said beam-element pairs 14, 15a and 14, 15b respectively, although, in accordance with the invention, this frame-structure holding function of the posts can be taken over by the edge-pieces 12 and 13 which, in such cases, are firmly connected to the beam-elements 14, 15. When the frame structure 11 is held together by posts 18, the edge-pieces 12, 13 can be given some other suitable design for holding the beam-element pairs at a predetermined distance apart at the front and the rear part of the baffle respectively. The end-pieces may also be designed for a snap-fastening action.

[0017] Figure 3 shows a baffle 10 from above. The lower part of said Figure shows the front end-piece 12 fastened to the upper beam-elements 14a and 14b of the baffle-parts 16a,b by means of fasteners 19, for instance rivets. These fastener devices may, however, be replaced by spot welds or other, similar simple fastener systems. The rear edge-piece 13 can also be fastened with fasteners 19 in a similar manner. The space 17 between the baffle-parts 16a and 16b narrows towards the far end, or distal end, of the baffle 10 in this illustration. It will be apparent from this view that the baffle-parts 16a and 16b can be disposed at varying angles to one another, by appropriate selection of the width of the rear edge-piece 13, wherewith the baffle 10 obtains a varying degree of taper. As before mentioned, the side surfaces 23 of the baffle-parts 16 in the assembled state of the sound absorber will face towards adjacent air ducts in said absorber.

[0018] Figure 4 is a cross-sectional view of the baffle shown in Figure 3, taken on the line A-A in said Figure. The illustrated baffle-part 16a is comprised of the upper beam-element 14a, the associated lower beam-element 15a, a sheet 20 of sound-insulating material between said elements, and glass-fibre cloth 22 that covers the surface of the sound-insulating material at least at its outer parts that will border on the air flow. Filling material 21 is placed in the space 17 between the baffle-parts 16a and 16b, this material being either a sound-insulating material or a material that has some other main function in the baffle 10.

[0019] The inventive baffle has several advantages over known, similar baffles. The most important of these advantages is that

• the baffle is easy to produce and install;
• significant savings in material are obtained;
• the baffle is variable and flexible;
• external insulation material can be chosen independently of remaining baffle-contents;
• the width and taper of the baffle can be readily adapted by corresponding selection of the edge-pieces;
• a standard module can be used for each baffle-part, regardless of baffle width; and
• the baffle can be made lighter than earlier known baffles.

Claims

1. A baffle for sound absorbers intended for rectangular ventilation ducts, wherein said baffle (10) has a rectangular shape when seen sideways on and also when seen in vertical cross-section transversely to its longitudinal axis, and wherein said baffle includes sound absorbing insulating material (20, 21) and a frame structure or casing (14, 15) that supports said insulating material, characterised in that the baffle includes at least two juxtaposed baffle-parts (16) of generally parallelepipedic shape and mutually spaced at least at one end thereof and contains sound absorbing insulating material (20) and said insulating-material supporting frame structure or casing (14, 15); in that said baffle also includes vertical edge-pieces (12, 13) which hold said baffle-parts (16) together at the outer ends of the baffle (10), wherein at least one edge-piece (12) at the outer baffle end which meets the ventilation air has an air-flow deflecting shape; in that said baffle-parts (16) are given a predetermined position in relation to one another by corresponding selection of the edge-pieces (12), such as to form spaces (17) between two mutually adjacent baffle-parts (16).

2. A baffle according to Claim 1, characterised in that the baffle-parts (16) are disposed obliquely in relation to one another such that the baffle (10) will be thickest at that end which shall be positioned to meet the air flow in the ventilation duct.

3. A baffle according to Claims 1 and 2, characterised in that at least one space (17) between said baffle-parts (16) is filled with an appropriate material (21).

4. A baffle according to Claim 3, characterised in that said material is a sound absorbing material.

5. A baffle according to Claims 1-4, characterised in that the front edge-piece (12) is curved and has a resilient or spring function with respect to said baffle-parts (16).

6. A baffle according to Claims 1-5, characterised in that each baffle-part (16) includes a frame structure (14) that has two upper and two lower horizontal U-shaped beam-elements (14, 15) which accommodate and support a sheet (20) of sound absorbing material.

7. A baffle according to Claim 6, characterised in that the sheet (20) of sound absorbing material in each baffle-part (16) is comprised of mineral wool covered with glass-fibre cloth (22) on both sides.

8. A baffle according to Claims 1-7, characterised in that the height of the baffle is adapted to the duct dimensions in question.

9. A baffle according to Claims 1-7, characterised in that the height of the baffle corresponds to an even multiple of the height of the duct in question.

Drawing