Sound-damping ventilating device

Abstract: A sound-damping ventilating device comprising a block-shaped housing (6), substantially elongated in the direction of its width, having an air inlet (2) and an air outlet (3) extending substantially throughout the entire width of the housing (6) and being connected via a channel (15) having at least one of its walls partly formed by sound-damping material (11) accommodated in a substantially U-shaped metal casing (12), the free ends of the legs of the U-shape being bent towards each other and these bent ends also being part of the channel wall, while the channel (15), over at least a part of its length between the inlet and the outlet, is divided into at least two parts by a plate-shaped member (16), arranged in the channel (15), made from an acoustically hard material and disposed above the open part of the U-shape.

Description: This invention relates to a sound-damping ventilating device comprising a block-shaped housing, substantially elongated in the direction of its width, having an air inlet and an air outlet extending substantially throughout the entire width of the housing and being mutually connected within the housing via a channel having at least one of its walls partly formed by sound-damping material accommodated in a substantially U-shaped metal casing, the free ends of the legs of the U-shape being bent towards each other and these bent ends also being part of the channel wall, while the channel, over at least a part of its length between the inlet and the outlet, is divided into at least two parts by at least one element arranged in the channel. Such a sound-damping ventilating device is disclosed in non-prepublished Netherlands patent application 89.03189. The element that divides the channel into two parts is a layer of sound-damping material having its longitudinal edges encased in two metal U-sections. By dividing the channel, while maintaining an equal rate of air flow, improved sound-damping is obtained, inter alia as a result of the additional amount of sound-damping material accommodated in the element arranged in the channel. The object of the present invention is to improve a sound-damping ventilating device of the type described in the opening paragraph hereof, in such a manner that the impedance of the channel is favourably influenced to a still further degree, i.e., the sound-damping action is still further enhanced. This is accomplished in accordance with the invention in that the element is a plate-shaped member made from an acoustically hard material, such as a metal, which plate-shaped member is disposed above the open part of the U-shape. Through these features, a considerable improvement of the sound-damping properties of the ventilating device is obtained, along with a decrease of the outside dimensions of the ventilating device inasmuch as a body has been replaced with a plate made from an acoustically hard material. This achievement is realized by making use of the fact that the U-shaped casing of the sound-damping material is in fact a resonator and the element made from acoustically hard material immediately reflects the sound waves coming from the resonator, so that the efficiency of the resonator is increased. Sounds of low frequencies in particular can thus be damped considerably more effectively. In order to maximize the reflective action, it is preferred, in accordance with a further embodiment of the invention, that the plate-shaped member overlaps the free edges of the bent ends of the U-shape. The plate-shaped member has a double effect when, in accordance with a further embodiment of the invention, both channel walls are each partly formed by sound-damping material accommodated in a substantially U-shaped metal casing, the free ends of the legs of the U-shape being bent towards each other and these bent ends also being part of the channel wall, while the open parts of the U-shape are directed towards each other and the plate-shaped member overlaps the free edges of the bent ends of the two U-shapes. An extension of the channel, resulting in further improved sound-damping, can be obtained when, in accordance with a further embodiment of the invention, viewed in cross-section, one U-shape projects relative to the other U-shape, while on the projecting side the leg of the projecting U-shape is extended to a point in front of the other U-shape, so that an L-shaped channel is obtained which, at least over a part of its length, is divided into two parts by a correspondingly L-shaped plate-shaped member. At the same time, this provides in a simple manner an effective shield preventing rain from entering the device. In certain conditions, within a sound spectrum to be damped, a particular predominant frequency can be so disturbing as to make additional provisions necessary. In that case, it is possible, and in accordance with a further embodiment of the invention, to arrange a Helmholtz resonator below the recessed U-shape, while the extended leg of the projecting U-shape and the L-shaped plate-shaped member extend to a point in front of the resonator opening, for instance formed as a stub or a slot. It is known per se to use a Helmholtz resonator for such a purpose, but in this case, too, using the teaching of the present invention, the action of that Helmholtz resonator is improved by arranging for the plate of acoustically hard material to extend beyond the opening of the Helmholtz resonator. Naturally, Helmholtz resonators can also be arranged at other points within the ventilating device. As long as the opening of such a resonator is covered, at a short distance therefrom, by the plate, the improved sound-damping action according to the invention is obtained. With reference to the embodiments schematically shown in the drawings, the sound-damping ventilating device according to the invention will now be further discussed and explained. In these drawings: Fig. 1 is a cross-sectional view of a first embodiment; Fig. 2 is a cross-sectional view of a second embodiment; and Fig. 3 is a cross-sectional view of a third embodiment. The sound-damping ventilating device shown in Fig. 1 comprises an elongated, tubular housing 1 having an air inlet 2 and an air outlet 3. The air inlet 2 can be shut off by means of a schematically shown valve 4, which can be controlled for instance by means of a knob 5. The valve 4 can be of a generally used type, for instance a slide comprising an outer plate provided with a plurality of ventilating apertures and, cooperating therewith, an inner plate having similar ventilating apertures, the arrangement being such that the plates can be positioned relative to each other by means of the control knob 5, in such a manner that in a first extreme, open position, the ventilating apertures in the inner plate align with the ventilating apertures in the outer plate and in a second extreme, closed position, the ventilating apertures in the outer plate are entirely covered by inner plate portions located between the ventilating apertures of the inner plate. Further, by means of the control knob 5 any position intermediate the entirely open and the entirely closed position can be obtained by a corresponding mutual adjustment of the two plates. Optionally, a second pair of plates, likewise provided with ventilating apertures and spaced from the first pair of plates, can be controlled simultaneously by means of the control knob 5, so that a valve with an effective double seal can be obtained. The housing 1 comprises a top wall 6, a bottom wall 7 and two end walls 8. Between these end walls, two section parts extend in downward direction from the top wall 6. A section part 9, which is J-shaped in cross-section, extends adjacent the air inlet 2 and an L-shaped section part 10 extends adjacent the air outlet 3. Together with the top wall, section parts 9 and 10 form a U-shaped casing for a block 11 made from sound-damping material. Two section parts extend upwards from the bottom wall 7. Adjacent the air inlet 2 extends a section part 12 which is J-shaped in cross-section and adjacent the air outlet 3 extends an L-shaped section part 13. Section parts 12 and 13 extend from one end wall 8 to the other end wall 8 and, together with the bottom wall, form a U-shaped casing for a block 14 made from sound-damping material. The free ends of the section parts 9 and 10 are in line and extend parallel to the section parts 12 and 13 which in turn are in line with each other. The free ends referred to form a part of the wall of a channel 15 extending between the inlet 2 and the outlet 3. Between the free ends of the section parts 9 and 10, and 12 and 13, respectively, the channel 15 is bounded by one side of blocks 11 and 14 respectively. The channel 15, throughout the greater part of its length between the inlet 2 and the outlet 3, is divided into two parts by a plate 16 made from an acoustically hard material, for instance metal. The plate 16 is longer than the portion of the channel wall formed by block 11 or block 14 and extends beyond the two ends of those channel wall portions. The plate 16, like the section parts 9, 10, 12 and 13, extends from one end wall 8 to the other end wall 8 and can be connected to these end walls 8 to be retained in position. The plate 16 can further be retained in position by local supports (not shown) which are connected for instance to the section parts 9, 10, 12 and 13. The U-shaped casing 10, 6, 9 of block 11 and the U-shaped casing 13, 7, 12 of block 14 each form a resonator body. Plate 16 provides that the sound waves are reflected into the resonators as fast as possible and, upon their leaving the resonators, are reflected back into the resonator again as much and as fast as possible. Thus, by arranging the plate 16, the action of the sound-damping means provided is rendered considerably more effective. Fig. 2 shows a ventilating device 20 accommodating an upper block 21 made from sound-damping material surrounded by a casing 22 which is open in downward direction, and a lower block 23 made from sound-damping material surrounded by a casing 24 which is open in upward direction. Between the two blocks 21 and 23 extends a channel 26 from an inlet 25 to an outlet 27. Arranged adjacent the inlet 25 is a shut-off valve 4 fitted with a control knob 5 of the type discussed with reference to the embodiment shown in Fig. 1. Relative to this embodiment, the channel between the two blocks has been extended by arranging for the upper block 21 to project relative to the lower block 23 and by extending the front wall of the casing 22 in downward direction, so that an L-shaped channel is obtained, which is divided into two parts by means of a correspondingly L-shaped plate 28 made from an acoustically hard material, such as a metal. It is observed that block 11, and hence the casing thereof, has different cross-sectional dimensions than block 14 and hence the casing thereof. Thus, as to their dimensions, the two casings are tuned to damping mutually different frequencies, for instance, in particular low frequencies in the spectrum of frequencies to be damped. By filling up the casings with sound-damping material, on the one hand an effective damping of high-frequent sound is obtained, while, on the other, this results in a broadening of the range which the resonator is tuned to, although this entails a leveling down of the damping efficiency of the design frequency. If this leveling down of a particular frequency is considered undesirable, a ventilating device 30 according to Fig. 3 can be opted for. In Fig. 3 similar parts to those in Fig. 2 are indicated by the same reference numerals. In order to optimally damp a specific frequency, in the embodiment according to Fig. 3 a part of the block 23 shown in Fig. 2 has been replaced with a Helmholtz resonator 31 which is tuned to the frequency referred to. The Helmholtz resonator 31 has an access opening or slot 32 which, at a short distance therefrom, is covered by the plate 28, so that the damping action of this resonator is improved. The same resonator can also be used in the embodiment according to Fig. 1. In order to obtain the enhancing effect of the plate 16, the access slot may be situated as indicated by broken lines 32a in Fig. 3. It goes without saying that the embodiments described above and shown in the figures only serve to illustrate the invention and do not limit the invention to the embodiments shown. Within the framework of the invention as defined in the appended claims, many modifications and variants are possible. For instance, it is possible to use one instead of two blocks of sound-damping material or replace a block with one or more Helmholtz resonators of which the access openings are preferably located opposite the plate at a short distance therefrom. Further, the slide 4 can be replaced with any other suitable shut-off means, which may be arranged at any desired point in or on the housing. For instance, swiveling valves may be provided at the outlet or outlets, and such swiveling valves can also be used in combination with a slide 4, so that the inlet and outlet can be shut off. In principle, it is also possible not to use any shut-off means at all.

Claims: A sound-damping ventilating device comprising a block-shaped housing (6), substantially elongated in the direction of its width, having an air inlet (2) and an air outlet (3) extending substantially throughout the entire width of the housing (6) and being mutually connected within the housing via a channel (15) having at least one of its walls partly formed by sound-damping material (11) accommodated in a substantially U-shaped metal casing (12), the free ends of the legs of the U-shape being bent towards each other and these bent ends also being part of the channel wall, while the channel (15), over at least a part of its length between the inlet and the outlet, is divided into at least two parts by at least one element arranged in the channel, characterized in that the element is a plate-shaped member (16) made from an acoustically hard material, which plate-shaped member is disposed above the open part of the U-shape. A sound-damping ventilating device according to claim 1, characterized in that the plate-shaped member (16) is made from metal. A sound-damping ventilating device according to claim 1 or 2, characterized in that the plate-shaped member (16) overlaps the free edges of the bent ends of the U-shape. A sound-damping ventilating device according to any one of the preceding claims, characterized in that both channel walls are each partly formed by sound-damping material (11) accommodated in a substantially U-shaped metal casing (12), the free ends of the legs of the U-shape being bent towards each other and these bent ends also being part of the channel wall, while the open parts of the U-shape are directed towards each other and the plate-shaped member (16) overlaps the free edges of the bent ends of the two U-shapes. A sound-damping ventilating device according to claim 4, characterized in that, viewed in cross-section, one U-shape (21) projects relative to the other U-shape (23), while on the projecting side the leg of the projecting U-shape is extended to a point in front of the other U-shape, whereby an L-shaped channel (26) is obtained which, at least over a part of its length, is divided into two parts by a correspondingly L-shaped plate-shaped member (28). A sound-damping ventilating device according to claim 5, characterized in that a Helmholtz resonator (31) is arranged below the recessed U-shape, while the extended leg of the projecting U-shape (21) and the L-shaped plate-shaped member (28) extend to a point in front of the opening of the resonator.

Inventors: ZWAAN ADRIANUS JACOBUS, ZWAAN, ADRIANUS JACOBUS
Applicants: ZWAAN ADRIANUS J, ZWAAN, ADRIANUS JACOBUS
Application year: 1992
Main classification: E06B7
IPC codes: F24F13, E06B7