Device for reduction of disturbing noise in a flow control device

Claim 2

In a casing having walls defining an air passage a flow control assembly of the type including a baffle or threshold projecting into the air passage from one wall of said casing toward an opposed wall of said casing, said threshold having an arcuate concave surface facing upstream, a plate or pressure plane disposed upstream of said threshold and mounted for rotation about an axis transverse to the axis of the casing such that its downstream end moves parallel to said arcuate face of said threshold, an arcuate valve blade carried at the downstream end of said pressure plane for forming an adjustable throttling gap between said threshold and said opposed wall of said casing, there being a fixed gap between said valve blade and said pressure plane, the improvement comprising air guiding means disposed upstream of said arcuate valve blade forming separate first and second channels leading to said adjustable throttling gap and to said fixed gap, respectively, said channels having cross sectional areas which decrease in the direction of air flow whereby air turbulence and associated noise in said gaps are reduced.

Claim 3

Apparatus as in claim 1 wherein said air guiding means includes two surfaces diverging in a downstream direction from a common edge which extends transversely of the air passage whereby the first channel is formed in part by one of said diverging surfaces and said one wall of said casing and whereby the second channel is formed in part by the other diverging surface and said opposed wall of said casing.

Claim 4

Apparatus as in claim 1 wherein said air guiding means includes a hollow body having an axis extending transversely to said air passage, said body comprising said arcuate valve blade as one of its walls and comprising two side surfaces diverging in a downstream direction from a common edge which extends transversely to said air passage.

Claim 5

Apparatus as in claim 3 wherein said hollow body is provided with two end surfaces extending upstream of said two side surfaces.

Claim 6

In a casing having walls defining an air passage a flow control assembly of the type including a baffle or threshold projecting into the air passage from a wall of said casing toward an opposed wall of said casing, said threshold having an arcuate surface facing upstream, a plate or pressure plane disposed upstream of said threshold and mounted for rotation such that its downstream end moves parallel to said arcuate face of said threshold, an arcuate valve blade carried at the downstream end of said pressure plane for forming an adjustable throttling gap between said threshold and said opposed wall of said casing, there being a fixed gap between said valve blade and said pressure plane, the improvement comprising air guiding means disposed upstream of said arcuate valve blade said air guiding means including a hollow body having an axis extending transversely to said air passage, said body comprising said arcuate valve blade as one of its walls and comprising two side surfaces diverging in a downstream direction from a common edge which extends transversely to said air passage, one side surface of said body facing said opposed wall of said casing and being concave and the other side surface of said body facing said pressure plane and being generally flat, said body forming separate channels leading to said adjustable throttling gap and to said fixed gap, respectively, said channels having cross sectional areas which decrease in the direction of air flow whereby air turbulence and associated noise in said gaps are reduced.

Claim 7

In a casing having walls defining an air passage a flow control assembly of the type including a baffle or threshold projecting into the air passage from a wall of said casing toward an opposed wall of said casing, said threshold having an arcuate surface facing upstream, a plate or pressure plane disposed upstream of said threshold and mounted for rotation such that its downstream end moves parallel to said arcuate face of said threshold, an arcuate valve blade carried at the downstream end of said pressure plane for forming an adjustable throttling gap between said threshold and said opposed wall of said casing, there being a fixed gap between said valve blade and said pressure plane, the improvement comprising air guiding means disposed upstream of said arcuate valve blade said air guiding means including a hollow body having an axis extending transversely to said air passage, said body comprising said arcuate valve blade as one of its walls and comprising two side surfaces diverging in a downstream direction from a common edge which extends transversely to said air passage, one side surface of said body facing said opposed wall of said casing and being concave and the other side surface of said body facing said pressure plane and being generally flat, said body forming separate channels leading to said adjustable throttling gap and to said fixed gap, respectively, said channels having cross sectional areas which decrease in the direction of air flow whereby air turbulence and associated noise in said gaps are reduced.

Claim 8

Apparatus as in claim 5 wherein said generally flat surface has a dimension along the air flow direction which is about 0.3 to 0.4 times the dimension between said walls of said casing, wherein said edge formed by said body is disposed a distance above the axis of rotation of said pressure plane which is about 0.1 to 0.2 times said dimension between casing walls and wherein said concave side wall of said body has a radius of curvature which is about 0.3 to 0.5 times said dimension between said casing walls.

Claim 9

Apparatus as in claim 5 wherein said opposed wall of said casing terminates in an edge which faces downstream and wherein said arcuate valve member has a free edge which engages said just mentioned edge in a closed position of said flow control assembly.