AN EXHAUST SILENCER

Abstract: An exhaust silencer comprises an inner, flexible pipe (2), an outer casing (4) and a noise-suppressing material (3) between the pipe (2) and the outer casing (4). The casing comprises a strip (41) wound helically with partial overlap. A curable adhesive (43) is arranged between the turns in the overlap region (42) and is selected to be cured after the exhaust pipe has been bent to the desired shape and fitted.

Description: An exhaust silencer The present invention relates to an exhaust silencer of the type comprising an inner, flexible pipe, an outer /% casing and possibly a noise-suppressing m such as i* aterial mineral wool, steel wool or the like between the pipe and 5 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 10 have been made to furnish the exhaust pipe with two proper¬ ties 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 15 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 un¬ intentional bending. The alternative is a relatively large number of points for attaching the exhaust pipe to the 20 vehicle. An object of the invention is therefore to produce 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 25 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 30 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 thermo- setting 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. Alternativley 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 immedia¬ tely 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. The invention, defined in the appended claims, will now be described with reference to an embodiment illustrated only schematically. Figure 1 shows schematically an axial section through a preferred inner pipe in the exhaust pipe accor¬ ding to the invention, and also intimates a method of manufacture. Figure 2 shows schematically an axial section through an exhaust pipe according to the invention. It can be seen that the pipe 2 in Figure 1 is formed of sheet-metal rings 10 consisting generally of cylindrical 5 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 Figure 1, the larger flange 6 of a ring 10 is fitted the smaller 10 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 flange 6 so that it is shrunk over the flange 7, thus forming a joint 1 of ball-and- socket type. The upsetting may possibly be arranged to 15 offer predetermined friction between adjacent rings 10 so that they remain in the position obtained at the bending operation. Figure 2 shows that the pipe 2 may be provided externally with a noise-suppressing material 3, such as a layer of 20 mineral wool, steel wool or the like. The pipe 2, with the noise-suppressing material 3 if any, is then provided with a casing 4. The casing 4 comprises at least one strip 41 wound helically with partial overlap 42 between adjacent turns. A curable adhesive 43 is also 25 provided in the overlap region between the turns. The strip 41 is preferably coated with curable adhesive 43 over its entire inner side. ] The casing 4 may also include a second strip 141 which is i wound outside the strip 41, without overlap 142 between 30 adjacent turns, a curable adhesive 143 being provided at least in the overlap region in order to bind the winding turns together at curing. The adhesive 143 is preferably applied across the entire width of the strip 141, so that the strip 141 will adhere to the first helically wound strip 41. It will be understood that the inner pipe 2 shown in Figure 2 can easily be bent to the desired shape, while retaining an unrestricted cross section, and without noticeable resistance from the casing 4 or noise-suppressing material 3. The exhaust pipe can then be permanently fixed in the required shape by curing of the adhesive. To produce an exhaust system for a private car, for in¬ stance, an exhaust pipe according to Figure 2 can be cut to the desired length and then bent to a shape suitable for the make and model of the car. While the exhaust pipe is still in the moulding device, the curable adhesive 43 can be hardened and the pre-shaped exhaust pipe can then be fitted in conventional manner. Alternatively, the exhaust pipe shaped in a bending operation can be fitted without curing and the adhesive 43, 143 can then be cured by the hot exhaust fumes which will then flow through the exhaust system. However, it is evident that some other type of curable adhesive may also be used, such as one which hardens under the influence of a component from the environment, such as moisture from the atmosphere. In this case, the exhaust pipe should be provided with an air-tight wrapping after manufacture, which will prevent the adhesive from hardening until the wrapping is intentionally removed at the time the pipe is to be given the desired shape and fitted.

Claims: C l a i m s 1. An exhaust silencer comprising an inner, flexible pipe (2), an outer casing (4) and possibly a noise-suppressing material (3) between the pipe (2) and the outer casing (4) , w h e r e i n the casing (4) comprises a strip (41) wound 5 helically with partial overlap, a curable adhesive (43) being arranged between the turns in the overlap region (42). 2. An eshaust pipe as claimed in claim 1, w h e r e i n a second strip (141) is wound helically on the first strip (41), the direction of winding being opposite to that of 10 the first strip (41). 3. An exhaust pipe as claimed in claim 2, w h e r e i n the second strip (141) is wound with partial overlap and a curable adhesive (143) is arranged in the overlap region (142). 15 4. An exhaust pipe as claimed in any of claims 1 - 3, w h e r e i n the strip (141, 143) is coated with the curable adhesive over the entire width of its inner surface. 5. An exhaust pipe as claimed in any of claims 1 - 4, w h e r e i n the curable adhesive is a thermosetting 20 adhesive. 6. An exhaust pipe as claimed in claims 1 - 4, w h e r e i n the adhesive is curable when subjected to a component of the environment such as moisture from the atmosphere, and that the exhaust pipe is provided with an " ■ 25 air-tight wrapping intended to be removed immediately before the exhaust pipe is to be fitted.

Inventors: MALMSTEN SVEN-OLOF, MALMSTEN, SVEN-OLOF
Applicants: DORCHESTER ENTERPRISES LTD, MALMSTEN SVEN O, DORCHESTER ENTERPRISES LTD., MALMSTEN, SVEN-OLOF
Application year: 1989
Main classification: F01N7
IPC codes: F01N1, F01N7, F16L9