GB403651A - Silencer for gaseous currents - Google Patents

Abstract

403,651. Silencers for gaseous currents. BURGESS LABORATORIES, Inc., C. F., Madison, Wisconsin, U.S.A.-(Assignees of Jack, W. A. ; Madison, Wisconsin, U.S.A.) June 20, 1932, No. 17411. Convention date, June 20, 1931. [Class 7 (ii).] A silencer for gaseous currents comprises a conduit which permits of a substantially unobstructed gas flow and has a wall of soundabsorbing material, and a side branch chamber in communication with said conduit. The branch chamber acts as an acoustic filter and is effective in removing low frequencies, the high frequencies being removed by the absorbing material. A casing 10, Fig. 1, has end openings 11, 12 either of which may be used as inlet and the other as outlet. A duct 13 extends from one of the openings and has a perforated wall surrounded by filling material of the kind mentioned in Specification 312,937, [Class 7 (ii), Internal-combustion engines, Arrangement &c. of], to act as an absorbing medium. Between the filling material and casing is the side branch chamber 17 connected with duct 13 by a passage 19. The diameter of duct 13 may vary with respect to opening 11. In a modification, the duct 13 is extended across the passage 19 to opening 11. In a further modification, Fig. 3, (not shown), the passage 19 is near the centre of the duct 13 thus giving branch chambers of unequal length. In Fig. 4, the duct 13 and its absorbing covering are longer than the casing 10, and one end projects into an extension 50 of the casing. In a modification, Fig. 5, (not shown), the duct 13 and wall 14 terminate short of the casing and an imperforate portion of duct 13 extends into an enlarged inlet pipe 11. In Fig. 6 the absorbing material 23 is arranged around the branch chamber 17. In Fig. 7, (not shown), an annular baffle is arranged around the entrance of passage 19 into chamber 17. In Fig. 8, a silencer as described in Specification 312,937 is modified by the insertion of a branch chamber 28 communicating with duct 13 by a passage 29 provided with a baffle 30. The walls of chamber 28 may be of foraminous material. In a modification, Fig. 9, (not shown) the branch chamber is situated at the end of the casing 10 adjacent the inlet 11. In Fig. 10, (not shown), applicable as an intake silencer wherein the gas flow and sound travel are in opposite directions, and a change of direction of gas flow is necessary, the branch chamber is of T-form surrounded by the absorbing material. The order in which the two types of silencing means are arranged with respect to the gas flow depends upon the characteristics of the sound to be silenced.