Acoustics – Sound-modifying means – Muffler – fluid conducting type
Patent
1990-12-13
1992-11-10
Gellner, Michael L.
Acoustics
Sound-modifying means
Muffler, fluid conducting type
181248, 181252, 181282, F01N 708
Patent
active
051626225
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust silencer of the type comprising an inner, flexible pipe, an outer casing and possibly a noise-suppressing material such as mineral wool, steel wool or the like between the pipe and the outer casing.
The known technology, represented by Swedish Patents No. 73 11 076-9 and No. 85 00 785-4 and British Patent No. 1 191 124, for instance, proposes a flexible or bendable exhaust silencer. The problem with this is that attempts have been made to furnish the exhaust pipe with two properties which are in opposition to each other. On the one hand the exhaust pipe shall be flexible or bendable while retaining an unrestricted cross section, and on the other hand the shape obtained during the bending operation must be retained after the pipe is fitted, for instance on the lower side of a private car, where the exhaust pipe may be subjected to considerable inertial force resulting in unintentional bending. The alternative is a relatively large number of points for attaching the exhaust pipe to the vehicle.
SUMMARY OF THE INVENTION
An object of the invention is therefore to provide an exhaust pipe of the type described in the introduction, by means of which said drawbacks are eliminated.
An exhaust silencer according to the invention is thus of the type comprising an inner, flexible pipe, an outer casing and possibly a noise-suppressing material between the pipe and the outer casing, the exhaust pipe being characterised in that the casing comprises a strip wound helically with partial overlap, a curable adhesive being arranged between the turns in the overlap region. According to one embodiment a second strip may be wound helically on the casing, the direction of winding being opposite to that of the strip comprising the casing. The second strip may also be wound with partial overlap and a curable adhesive is arranged between the turns, at least in the overlap region. One or both strips may be coated on the inner side with the curable adhesive. The outer strip will then adhere to the outer side of the first helically wound inner strip. The curable adhesive may be a thermosetting adhesive, allowing stabilization of the casing due to the heat from the exhaust fumes, for instance, when the exhaust pipe is fitted in a motor vehicle. Alternatively the adhesive may be curable when subjected to a component of the environment such as air or moisture, in which case the exhaust pipe is provided immediately after manufacture with an air-tight wrapping intended to be removed immediately before the exhaust pipe is to be fitted, such as when the exhaust pipe is being bent.
The inner pipe may in principle be of any type. However, a pipe formed of relatively short pipe sections jointed by means of upset joints of ball-and-socket type is preferred so that the axial length remains constant even when bent. This reduces the risk of gaps appearing between the turns of the casing strip when the pipe is subjected to force such as axial stretching during bending operations.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention, defined in the appended claims will now be described with reference to an embodiment illustrated only schematically in the drawings, in which:
FIG. 1 shows schematically an axial section through a preferred inner pipe in the exhaust pipe according to the invention, and also suggests a method of manufacture.
FIG. 2 shows schematically an axial section through an exhaust pipe according to the invention.
DETAILED DESCRIPTION
It can be seen that the pipe 2 in FIG. 1 is formed of sheet-metal rings 10 consisting generally of cylindrical perforated elements with externally generally concave cross-sectional profile 5, the sections 6, 7 being of different lengths. The perforations 8 serve to facilitate noise suppression in the exhaust. As indicated in FIG. 1, the larger flange 6 of a ring 10 is fitted the smaller flange 7 onto an adjacent ring 10 in the direction of the arrow 11, a radially inwardly directed uppsetting force 12 being applied to the ring f
REFERENCES:
patent: 2718273 (1955-09-01), Dehaus
patent: 4793384 (1988-12-01), Lalikos et al.
patent: 4851298 (1989-07-01), Fukuda
patent: 4854416 (1989-08-01), Lalikos et al.
patent: 4867269 (1989-09-01), Lalikos et al.
Dang Khanh
Dorchester Enterprises Ltd.
Gellner Michael L.
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