Patent GB-471431-A (GB)
Title: Improvements in and relating to silencers for gaseous currents
IPC: F16L55/033
Filed: 1936-03-03
Abstract: 471,431. Exhaust and like silencers ; filtering air. HEATHER, F. March 3, 1936, No. 6464. [Classes 7 (ii) and 7 (iii)] [Also in Group XXVIII] A silencer for gaseous currents, applicable to air compressors, the exhaust or intake of internal-combustion engines, the supply of cooling-air to electric motors or to air - conditioning apparatus, or the exhaust of pneumatic tools, comprises an outer casing with an interior passage for the flow of the gases formed by one or more helical elements having the coils spaced apart and sound-absorbing material fitting the interior of the casing. In one form, the silencer comprises a cylindrical casing with a central passage formed by the helical element and surrounded by soundabsorbing material such as felt, asbestos, rubber, or glass wool. Fig. 3 shows a casing a containing a sound-absorbing body d formed with passages g fitted with helical springs f. These springs project beyond plates h at each end of the body d into expansion chambers i, j, the projecting coils being closed up as shown. In another form, a central passage through the body d contains a helical spring and communicates with radial passages or pockets formed in the body and each fitted with springs. In Fig. 7, a series of helical springs m bent into annular form and filled with soundabsorbing material are arranged side-by-side to provide a central passage. Back-flow of gases may be prevented by a non-return flap valve fitted in the casing. In another form, a series of annular springs such as m, Fig. 7, are arranged in annular pockets formed in the sound-absorbing body surrounding a central helical spring. Again, several helical springs extending longitudinally within the casing are surrounded with sound-absorbing material, and a length of wire or hair brush material is inserted within each spring and may serve as an air filter in a carburetter intake. Fig. 19 shows another form in which annular spring members 2 are placed between discs x, z of sound-absorbing material which are alternatively formed with a central hole y or a ring of holes 1, all fitted with helical springs. In a modification of this form, the discs z are made of smaller diameter than the casing without the holes 1, and are surrounded by annular spring members. Again, the annular spring members 2 may be separated by rings formed by winding asbestos or glass-silk sheet, a helical spring being placed in the passage formed through the centre of the spring members and rings ; the casing may also be lined with the same sheet material. Fig. 23 shows a silencer and filter for the air intake of an engine, the body 14 of sound-absorbing material having a series of holes fitted with helical springs 16 filled with brush material 17, preferably moistened with oil to act as a filter for air entering under a hood 12 ; a hollow 21 in the body 14 communicates with a space 22 beneath it. In a similar construction, the body of sound-absorbing material is formed by coiling sheet material around a central helical spring, and interposing a number of other helical springs at various points between the coils, the brush material being placed within an annular spring member arranged above the body and under hood 12. A further form for the exhaust of pneumatic tools comprises two bodies 32, 33, Fig. 27, of sound-absorbing material formed with central pockets 34 and a number of smaller pockets 35, and having between them an annular spring member 37, the exhaust passing from the entry 35a to outlet apertures 38 in the casing. In another form adapted for the exhaust conduit of a Diesel engine or of an air-conditioning apparatus, the vertical conduit is lined with asbestos felt &c., radial holes or pockets in the lining being fitted with helical springs ; the radial holes at the top extend through the wall of the conduit to form outlets, and a helical spring extends through the conduit within the lining.