AN EXHAUST SILENCER AND A METHOD OF MANUFACTURING IT

Abstract: The exhaust pipe comprises an inner pipe, permeable to gas in radial direction, which is provided with a casing (4) and possibly with a noise-suppressing material (3) such as mineral wool inside the casing. The pipe (2) is produced by utilizing prefabricated perforated, generally cylindrical rings of strip material, said rings when considered in axial section having outwardly concave cross section (5), with cross-sectional legs (6, 7) of different lengths. The rings (10) are placed axially beside each other and are flexibly jointed to each other by the longer flange (6) of one ring (10) being upset over the shorter flange on an adjacent ring (10) to form a joint (1) of ball-and-socket type. The pipe (2) can be quickly and rationally manufactured with automatic equipment to the desired length and can be bent to the desired shape without noticeably altering the axial length of the pipe.

Description: An exhaust silencer and a method of manufacturing it The invention relates to an exhaust silencer of the type comprising an inner pipe, permeable to gas in radial di¬ rection, an outer casing and possibly a noise-suppressing material arranged between the pipe and the outer casing, in the form of mineral wool or metal wool such a steel wool or the like. The invention also relates to a method of manufacturing such an exhaust pipe, particulary the inner pipe therefor. The known technology is represented by Swedish Patents No. 73 11 076-9 and No. 85 00 785-4 and British Patent No. 1 191 125. According to the known technology the basic idea is to produce a bendable exhaust silencer, but the previous designs have several drawbacks both as regards manufacture and also as regards forming the exhaust pipe to the desired shape to fit a particular model of vehicle. It should be mentioned at this stage that although the exhaust pipe is particulary suitable for use in motor vehicles, other applications are perfectly feasible, e.g. ventilation systems or other fluid channel systems. One object of the invention is to provide a new exhaust silencer and a new method of manufacturing it, and also to offer a method for quickly and easily manufacturing an exhaust pipe which as well as being bendable to the desired shape, is also able to substantially maintain its axial length when bent, and even maintain its cross section. Further aims and advantages of the invention are revealed in the following description or will be obvious to one skilled in the art who studies the description. According to the invention, therefore, an exhaust silencer is proposed of the type comprising an inner pipe, permeable to gas in radial direction, an outer casing and possibly a noise-suppressing material arranged between pipe and casing, and according to the invention the exhaust pipe is charac¬ terised in that the inner pipe is formed from perforated rings of strip material, joined together axially, said rings when considered in axial section having outwardly concave cross section, with cross-sectional legs of diffe- rent lengths, the rings being flexibly jointed to each other, the longer flange of one ring being upset over the shorter flange of an adjacent ring. The pipe sections of the inner pipe preferably have an axial length which is less than their diameter. The pipe sections of the inner pipe are preferably connected together by means of upsetting, to form a joint of ball- and-socket type. The casing preferably consists of a curable material and is deformable prior to curing. It may comprise at least one layer produced from a strip material wound helically with partial overlap, e.g. metal strip material, with a curable adhesive between the turns in the overlap region. The casing may be arranged to be cured by the heat from the exhaust fumes after assembly in a motor vehicle. Alternatively the curable material may be arranged to be cured by air moisture or the like, in which case the exhaust pipe is provided immediately after manufacture with an air-tight wrapping intended to prevent premature hardening of the curable material. A method of manufacturing an exhaust silencer comprises producing an inner pipe, permeable to gas in radial direc¬ tion, and providing it with a casing and possibly with a noise-suppressing material between pipe and casing. The method is characterised substantially in that the pipe is produced by manufacturing perforated, generally cylindrical rings out of strip material, e.g. metal strip material, said rings when considered in axial section having outwardly concave cross section, with cross-sectional legs of diffe¬ rent lengths, the rings being placed axially beside each other and being flexibly jointed to each other by the longer flange of one ring being upset over the shorter flange on an adjacent ring. The pipe sections preferably have an axial length which is less than their diameter. The cross-sectional structure of the pipe sections and said upsetting are designed to create a joint of ball-and- socket type. Suitable adjustment of the upset will offer a certain friction in the joint designed to permit deformation of the pipe to the desired shape, the exhaust pipe thus obtaining a suitable shape for its proposed location. The exhaust pipe can thus easily be fitted and subsequently fixed permanently. According to a preferred embodiment, the exhaust pipe is made curable by means, for instance, of a curable material, so that its final shape is only fixed after the exhaust pipe has been fitted in its place of application. Curing may be arranged in conventional manner by means of heat from the exhaust fumes flowing through the pipe, or by means of moisture in the atmosphere surrounding the fitted exhaust pipe. The invention will be described by way of example with reference to the accompaying drawing illustrating an embo¬ diment shown only schematically. Figure 1 shows schematically an axial section through the inner pipe in the exhaust pipe according to the invention, at the time of manufacture of this inner pipe, and Figure 2 shows schematically an axial section through an exhaust pipe according to the invention. Referring first to Figure 2, it can be seen that the exhaust pipe according to the invention comprises an inner pipe 2, radially permeable to gas, a casing 4 surrounding the pipe 2 and a noise-suppressing material 3 arranged between the pipe 2 and the casing 4. The pipe 2 shown in Figure 1 is produced from generally cylindrical rings 10 of metal strip material. Seen in axial section, the rings have an outwardly concave cross section 5, the legs 6, 7 being of different lengths. The end of a new ring with larger diameter is passed over the end with smaller diameter on an adjacent ring, in the direction of the arrow 11. The flange 6 of larger diameter is then shrunk over the smaller flange 7 on the adjacent ring by means of a radially inwardly directed upsetting operation indicated by the arrows 12. Repetition of this process will gradually produce a pipe 2 of desired length. The flanges 6, 7 are dimensioned and shaped to give a joint of ball-and-socket type when subjected to the radial upsetting operation, thus allowing angular adjustment of adjacent rings 10 in relation to each other without sub¬ stantially altering their axial distance from each other. As shown in Figure 1, the rings 10 are provided with mult- iple perforations 8. Referring again to Figure 2, the exhaust pipe is produced by possibly providing the prefabricated pipe 2 externally with a noise-suppressing material 3, such as a layer of mineral wool, steel wool or the like, possibly in the form of an unbroken layer, and then applying a casing 4. In the example shown the casing 4 comprises a thin metal strip 41 wound helically with overlap 42 between adjacent turns. The strip 41 is provided at least in the overlap region with a curable adhesive 43. The adhesive 43 may be of thermosetting sype. It will then harden, thus solidifying the casing 4 and consequently the whole exhaust system, after the latter has been bent to the desired shape and fitted in the intended position, e.g. on a motor vehicle. If the exhaust pipe is to be used where it will not be subjected to sufficient heat to cure suitable adhesives, a curable adhesive can be used of a type which hardens under the influence of a component from the surrounding athrnos- phere, such as moisture. However, in this case the exhaust pipe should be provided with an air-tight wrapping immedi¬ ately after manufacture, to prevent premature hardening.

Claims: C l a i m s 1. An exhaust silencer comprising an inner pipe (2), permeable to gas in radial direction, 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 inner pipe is formed from perforated rings (10) of strip material, joined together axially, said rings when consi¬ dered in axial section having outwardly concave cross section (5), with cross-sectional legs (6, 7) of different lengths, the rings (10) ' being flexibly jointed to each other, the longer flange (6) of one ring being upset (12) over the shorter flange (7) of an adjacent ring (10). 2. An exhaust pipe as claimed in claim 1, w h e r e i n the axial dimension of the rings (10) is less than their inner diameter. 3. An exhaust pipe as claimed in claim 1 or 2, h e r e i n the cross-sectional profile and joint upsets of the rings are arranged to form a joint between them of ball-and-socket type. 4. An exhaust pipe as claimed in claims 1 - 3, h e r e i n the casing (4) consists of a curable material (43) and is deformable prior to curing. 5. An exhaust pipe as claimed in claim 4, w h e r e i n the casing (4) comprises at least one layer produced from a strip material (1) wound helically with partial overlap (42), with a curable adhesive (43) between the turns in the overlap region. 6. An exhaust pipe as claimed in claim 4 or 5, e r e i n the casing is arranged to be cured by the heat from the exhaust fumes passing through the exhaust pipe. 7. A method for manufacturing an exhaust silencer in which an inner pipe (2), permeable to gas in radial direc¬ tion is provided with a casing (4) and possibly with a noise-suppressing material between the pipe (2) and casing (4), w h e r e i n the pipe (2) is produced by manufac- turing perforated, generally cylindrical rings (10) out of strip material, said rings when considered in axial section having outwardly concave cross section (5), with cross- sectional legs (6, 7) of different lengths, the rings (10) being placed axially beside each other and being flexibly jointed to each other by the longer flange (6). of one ring (10) being upset over the shorter flange on an adjacent ring (10). 8. A method as claimed in claim 7, w h e r e i n the rings are shaped and upset to form a joint (1) of ball- and-socket type. 9. A method as claimed in claim 7 or 8, w h e r e i n the casing is produced from a strip-shaped material (41) wound helically and with partial overlap (42), and a curable material (43) is arranged in the overlap region, the adhe- sive being allowed to harden to stabilize the exhaust pipe once it has been given the desired shape.

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