NZ210394A - Exhaust silencer; helical core located by interference wrap-around of outer shell - Google Patents

Description

No.: Date: Priority Date(s): . liVT&f '.ft. 7%, 7$ft; . ^ .'p7^ Complete Specification Filed: Class: Publication Date: ...

P.O. Journal, No: fe.....

NEW ZEALAND PATENTS ACT, 1953 COMPLETE SPECIFICATION SUBSTITUTION Of A?fLOT _ UNDEB SECTION 24 1 IAU<V <5\i~£NiCe.fc-S C?<LoPPa^cnv^V*) UMiTfeo.

EXHAUST SILENCER I / qwtiPPUS-VENTHH of 9 Jan Cel 1 iers Street, Vryburg, Cape Province, Republic of South Africa, a South African citizen, hereby declare the invention for which I / XK« pray that a patent may be granted to me/&&>$ and the method by which it is to be performed, to be particularly described in and by the following statement: - 210395 THIS INVENTION relates to an exhaust silencer for an internal combustion engine. r According to the invention, an exhaust silencer includes a core providing at least one helical passage within a cylindrical shell, the silencer having an inlet opening at one end and an outlet opening at its opposite end, the helical passage being defined by at least one full turn of a vane arranged worm-screw fashion around a central axial support, the shell being of sheet metal tightly wrapped under tension around around the core and joined along a longitudinal seam "formed by overlapping longitudinal edges lying flat against the shell to provide ai radial interference fit with the core.

The central axial support may be in the form of a tube defining an axial flow passage and which is axially aligned with the inlet and outlet openings. The tube may be open at its upstream end, axially downstream from the silencer inlet opening, and closed by a transverse blocking piece at its downstream end which is upstream f rem the outlet opening. The tube may have openings through its wall in the downstream halF of its : length ,"up~stream ~frorn the transverse blocking piece preferably arranged in a cluster upstream of the"last downstream turn of the vane. The total | 'cross-sectional area of the openings out of the tube may be at least equal Yfep. the "cross-sectional area of the tube itself.

The inlet opening may be provided by an inlet connection which is funnel-shaped and which diverges in a downstream direction and connects with one end of the cylindrical shell, thereby forming an inlet chamber. The outlet opening may be provided by an outlet connection which is funnel-shaped and which connects with the opposite end of the cylindrical shell and which converges in a downstream direction from the cylindrical shell, thereby forming an outlet chamber.

The silencer may include a casing around the cylindrical * shell, a sound-insulating cavity being defined between the cylindrical shell and the casing. The cylindrical shell may be foraminous when surrounded by a casing.

The pitch of the vane may decrease in a downstream direction. The vane may have a wrinkled upstream surface. In a particular development, the vane may be made up of a pair of axially spaced upstream and downstream helical vane flights forming a vane or baffle having a sound-insulating helical cavity defined between the vane flights. The upstream vane flight may be foraminous.

The invention extends also to a method of making an exhaust silencer as described, which includes forming the core by wrapping a helical vane worm-screw fashion around a central axial support, and securing the vane thereto; partly forming the cylindrical shell from sheet metal material to have overlapping longitudinal edges for making a longitudinal seam; sliding the core with little radial clearance longitudinally into the thus partly-formed cylindrical shell; pressing the overlapping longitudinal edges of the shell together to form a longitudinal seam, thereby taking up radial clearance; and bending the seam over to lie flat against the cylindrical shell, the sheet metal material thereby being drawn tightly around the core and being placed under circumferential tension, the core being gripped frictionally and having a radial interference fit with the shell and being located axially in position within the shell.

In order to avoid having undulations in the outer surface of r the cylindrical shell after bending over of the seam, a helical mandrel may be used inside the shell and between the flights of the vane to serve as a platen or anvil on the inside of the seam for the bending over of the seam. The bending over may take place by means of a platen of a press or by means of hammering by hammers which may have heads of hide, or synthetic plastics material. The hammer head may be manually or machine operated.

The method may include the step of spot-welding the pressed-overlapping longitudinal edges of the formed seam together at longitudinally spaced intervals, before bending the seam over to lie flat against the cylindrical shell.

The invention extends still further to a method of making the core for a silencer having a vane with a wrinkled surface, the method including transversely wrinkling a sheet metal strip having a width and a wrinkled length corresponding to the radial length and overall length,of the vane respectively; ° - in 210394 wrapping the wrinkled strip edge-on worm-screw' fashion around a central axial support; and securing the inner edge of the helical worm thus formed to the central axial support.

The invention will now be described by way of exanple with reference to the accompanying diagrammatic drawings.

In the drawings, Figure 1 shows a sectional end elevation similar to that shown at I-I in Figure 5, through a cylindrical shell having a partly formed seam, after sliding of a core into it has taken place; ' Figure 2 shows a cross-section of a cylindrical shell similar to that shown in Figure 1, but after the seam has been pressed; Figure 3 shows a cross-section similar to Figures 1 and 2, but after the seam of Figure 2 has received an initial bend, immediately prior to bending the seam over onto the cylindrical shell; Figure 4 shows a cross-section of the shell after bending of the seam, shown in Figure 3, has taken place, to cause it to lie flat against the outer circumference of the shell; Figure 5 shows a part-longitudinal section at V-V in Figure 3,through a silencer which has been made in accordance with the invention; Figure 6 shows a part-longitudinal section at VI-VI in Figure 7, through another embodiment of a silencer which has been made 1n accordance with the invention; Figure 7 shows a cross-section as at VII-VII in Figure 6, showing a partly formed seam in an outer casing; C.fj&fc'., 210354 Figure 8 shows a cross-section similar to Figure 7, but with the seam pressed; Figure 9 shows a cross-section similar to Figures 7 and 8, but after the seam of the casing in Figure 8 has received an initial bend, 5 immediately prior to bending the seam over onto the outer circumference of the casing; Figure 10 shows a longitudinal section of yet another embodiment of silencer which has been made in accordance with the invention; Figure 11 shows a longitudinal section in composite form, showing 10 opposite ends of two different embodiments of silencers in accordance with the invention; Figure 12 showsa part sectional side elevation of a seam being pressed with a helical mandrel; and Figure 13 shows a side elevation of a helical mandrel.

Referring to the drawings, there is shown a cylindrical shell 10 of sheet metal 12 having a partly formed seam 13 having a longitudinal flange 14 of one edge of the sheet metal 12, overlapped by a hook formation 16 at the other longitudinal edge of the sheet metal 20 12. The hook formation has limbs 18 and 20. While the seam 13 is in Its partly formed state (as shown in Figure 1), a cylindrical core, generally indicated by reference numeral 22, and comprising a helical vane or baffle 23 arranged worm-screw fashion around a central axial tubular support 28, defining an axial flow passage 29 having an inlet 25 opening 28.1, is inserted slidably with little radial clearance 26, into the shell 10.

^ When the core 22 is in its correct axial position relative to 16 pEBT987 ends ^ the she11 10» then the 18 and 20 are folded over onto the flange 14 and pressed tightly together, as shown in Figure 2 of the drawings. The folding over of the limbs 18 and 20 and pressing them onto the flange 14 fully forms the partly formed seam 13 into a seam 30. At this stage, the seam 30 may be spot-welded at intervals along its length by means of electrodes 32. The spacing between adjacent spot welds may be of the order of 25 to 30 mm. After the seam 30 has been spot-welded, it is given an initial bend by being bent between two platens 34 of a press so that it lies at an angle, as shown in Figure 3, relative to the outer periphery of the cylindrical shell 10. The seam 30 is then pressed by platens 34 until it lies flat against the periphery, as shown in Figure 4. The pressing together of the limbs 18 and 20 and the flange 14, to form the seam 30, and the final pressing flat of the seam 30, causes the sheet metal 12 to be drawn tightly around the outer periphery of the core 22, thereby taking up the slight initial radial clearance 26, and to grip the core 22 frictionally. Thereby a radial interference fit is provided between the shell 10 and the core 22. The core 22 is thereby located axially in position within the shell 10.

Referring now to Figure 5 of the drawings, there is shown a silencer, generally indicated by reference numeral 40, in accordance with the invention. It includes a cylindrical shell 10 tightly gripping the core 22 and locating it in position axially within the shell 10. The core 22 includes the tubular central axial support 28 around which is wound the vane or baffle 23 in the form of a helical vane or worm. The vane or baffle 23 defines a helical passage 27.1 within the cylindrical shell 10, and has at least one full turn around the tubular central axial support 28. %' -x- - 0 - fl6FES!987-. 2 1039 The tubular central axial support in the form of the tube 28 is axially aligned with the inlet and outlet openings 44 and 46 of the silencer and provides an axial flow passage 29. The tube 28 is open at its upstream end 28.1, axially downstream from the inlet opening 44 and is closed by a blocking piece 28.2 at its downstream end 28.3, which is upstream from the outlet opening 46. The tube 28 has openings 28.4 through its wall, in the downstream half of its length, preferably upstream from the last turn 23.11 of the vane or baffle 23. The total cross-sectional area of the openings 28.4 out of the tube 28 is at least equal to the cross-sectional area of the tube itself.

The inlet opening 44 to the silencer 10 is provided by an inlet connection 48 which is funnel-shaped and which diverges in a downstream direction, forming an inlet chamber 48.1, and connects with the end 10.1 of the cylindrical shell 10. Likewise, the outlet opening 46 is provided by an outlet connection 50 which is funnel-shaped, forming an outlet chamber 50.1, and which connects with the opposite end 10.2 of the cylindrical shell 10. The funnel-shaped connection 50 defines the outlet chamber 50.1 and converges in a downstream direction from the end 10.2 of the cylindrical shell 10. The connections 48 and 50 are formed seamless from flat sheet material.

In accordance with a further development of the invention, an embodiment 51 (see Figure 6) is provided with a casing 52 around the cylindrical shell 10, a sound-insulating cavity containing damping or filler material 54, being defined between the cylindrical shell 10 and the casing 52. The cylindrical shell 10 in this embodiment is foraminous by being provided with openings 10.3. 210394 Referring to Figures 7 to 9 of the drawings, there is shown the method in which the outer casing 52 is wrapped tightly around the cylindrical shell 10 with an insulating layer 54 around it. In Figure 7, a partly formed outer casing 52.1 of sheet metal is shown. It has a partly formed seam 56 having a longitudinal flange 58 overlapped by a hooked formation 60 at the other longitudinal edge of the sheet metal. The hooked formation 60 has limbs 60.1 and 60.2. The casing 52 is then wrapped around the cylindrical shell 10 with a layer of insulating material 54, into the form shown in Figure 7 of the drawings. At this f stage, the layer of insulating material will already have been compressed to some extent. While the seam 56 is in its partly formed state, as shown in Figure 7 of the drawings, the limbs 60.1 and 60.2 are folded onto the flange 58 and pressed tightly together, as shown in Figure 8. In doing so, the casing 52 is drawn tightly around the periphery of the insulating layer 54 and the cylindrical shell 10. The casing grips the insulating layer 54 and shell 10 tightly.

The folding over of the limbs 60.1 and 60.2 and pressing them onto the flange 58 fully forms the partly formed seam 56 into a seam 57, as shown in Figure 8 of the drawings. At this stage, the seam 57 may be spot-welded at intervals along its length by means of electrodes 62. The spacing between adjacent spot welds may be of the order of 25 to 30 mm. After the seam 57 has been spot-welded, it is given an initial bend by being bent between two platens 34 of a press, so that it lies at an angle, as shown in Figure 9, relatively to the outer periphery of the casing 52. The seam 57, as shown in Figure 9, is then further pressed flat by platens 34 of a press (not shown) until it lies flat against the periphery, similar to that shown for the seam 30 of the cylindrical shell 10. The procedure adopted is very much the same as when the 2J.UoJ4 cylindrical shell 10 is wrapped around the core 22 in the making of the seam 30.

Further features of the invention are shown in Figures 10 and 5 11 of the drawings. Thus, the baffle or vane 23 may have a wrinkled surface provided by wrinkles or undulations 23.1 in the vane. In accordance with yet a further development, the baffle or vane 23 is made up of a pair of axially spaced upstream and downstream helical vane flights 23.2 and 23.3 forming a vane or baffle 23 having a r sound-insulating cavity defined between the vane flights 23.2 and 23.3. A further feature which can be introduced with this type of vane or baffle 23, is the provision of openings in the upstream vane flight 23.2 to make it foraminous. It will be understood, of course, that the invention is not limited to wrinkled surfaces for the upstream and 15 downstream flights of the vane or baffle 23 of Figure 11.

In the embodiment of Figure 10, the pitch PI of the vane 23, at the upstream end of the shell 10, ie downstream from the inlet opening 44, is larger than the pitch P2 at the downstream end 10.2 of 20 the shell 10. The pitch preferably varies uniformly between the upstream and downstream ends. The pitch P2 at the downstream end 10.2 of the helical passage may be only about half the pitch PI at or near the upstream end 10.1.

In use, the inlet connection 48 will be connected to the o exhaust pipe of an internal combustion engine, and the outlet connection 50 may have a tailpiece connected to it, if desired. The exhaust gases ^from the engine will enter the inlet chamber 48.1 of the silencer 40 in 16 FEB 19^7 ^ dlrectl0n arrow 6^5, and split into two flow paths, namely 210394 an axial flow path 29 along the tube 28, and a helical flow path indicated by arrows 27.1 along the helical passage 27.

In the embodiment of Figure 10, the conversion of the direction of flow from that of arrow 64 into the helical path 27, will take place gradually because of the small helix angle of the vane 23 at the inlet end of the helical passage 27. However^ as the exhaust gases pass further downstream along the helical passage, so the helix angle becomes greater and the developed length of the helical passage r increases per unit of axial length of the shell 10. The exhaust gases will flow generally in the direction as indicated by arrows 27.1. Thereafter, the gases will enter the converging funnel-shaped outlet connection 50, and will finally pass out of the silencer 40 in the direction of arrow 66.

The Applicant believes that the wrinkled surface 23.1 of a vane or baffle 23 will have a sound-absorbing effect on exhaust gases impinging on the vane surface. Furthermore, when a thick vane or baffle with a sound-absorbing cavity between the vane flights 23.2 and 23.3, is provided, and also when openings are provided in the upstream surface of the vane flight 23.2, then the sound-absorption capacity of the vane is increased.

The cross-sectional flow area of the helical exhaust passage provided by the vane or baffle 23 (whatever its shape or construction) within the cylindrical shell 10, is at least equal to that of the inlet and outlet openings, and is preferably greater. In a typical embodiment, the inner diameter of a shell 10 is 100 mm, the diameter of inlet and outlet openings 44 and 46 is 50 mm, and the diameter of the central axial support tube 28 is about 20 mm. 210394 Referring to Figures 12 and 13 of the drawings there is shown a press 70 having a helical mandrel 72 onto which a core assembly can be screwed prior to the bending over of the seam 30 to lie flat against the outer circumference of the shell 10. The press has a hydraulic cylinder and piston assembly 74, and a platen 76 for pressing against the seam 30 to bend it over against the shell 10.

The mandrel 72 may be machined from the solid to have coils 72.1 with gaps 72.2 in between to accommodate the vane 23 with slight axial clearance 72.4. The mandrel" has a central passage 72.3 to receive the central axial support 28. There is radial clearance 72.5between the bottom of the mandrel 72 and the shell 10. For use the mandrel is mounted cantilever fashion by means of a mounting flange 78.

The internal support provided by the mandrel to the inner surface of the seam during the bending over operation ensures a relatively smooth outer surface of the shell 10 without excessive undulations being formed by the tight stretchings of the shell over the core 22 where the shell bears or rides on the vane 23.

The mandrel 72 need have an axial length little more than half that of the shell and core assembly which has to be worked on it. When the seam 30 on one half of the shell 10 has been bent over, then the shell and core assembly is unscrewed from the mandrel and the other end is then screwed onto the mandrel 72 for bending over of the seam 30.

It will be evident.from the foregoing description and from the drawings that various combinations of shell, casing, core, and vane shape and construction are possible. The invention extends to the 2103 various possible combinations of these features as described and illustrated. Thus, the invention extends to silencers having the vane shapes or constructions of Figures 6, 10 and 11, but without an outer casing 52. Likewise, the plain vane 23 of Figure 5 may be used within a shell 10 having an outer casing 52. Furthermore, vane flights 23.2 and 23.3 may be plain and need not have wrinkles 23.1; only the upstream flight 23.2 need have wrinkles; both flights with or without wrinkles 23.1 may be foraminous; and a damper or filler material may be provided between flights 23.2 and 23.3, or may be left out, and when left out, * then openings in upstream and downstream flights are preferably out of axial alignment. Similarly, the variation in pitch of the vane 23 is applicable with all the different types or shapes of vanes described and shown. Likewise, the ratios of flow areas between helical passage and inlet and outlet openings apply, whatever the type or shape of vane. The various features described are also applicable with the various ratios of helical and axial flow passage lengths.

The Applicant believes that silencers in accordance with the invention can provide relatively inexpensive and good damping of the noise of the exhaust gases of an internal combustion engine, without excessive back pressure.

Claims (24)

if 21039$; WHAT T/WE CLAiM IS: CiOTlS

1. An exhaust silencer which includes a core providing at least one helical passage within a cylindrical shell, the silencer having an inlet opening at one end and an outlet opening at its opposite end, the helical passage being defined by at least one full turn of a vane arranged worm-screw fashion around a central axial support, the shell being of sheet metal tightly wrapped under tension around the core and joined along a longitudinal seam formed by overlapping longitudinal edges lying flat against the shell to provide a radial interference fit with the core.

2. A silencer as claimed in Claim 1, in which the central axial support defines an axial flow passage and which is in the form of a tube which is axially aligned with the inlet and outlet openings, and which is open at its upstream end, axially downstream from the silencer inlet j opening, and closed by a transverse blocking piece at its 1 downstream end which is upstream from the silencer outlet opening.

3. A silencer as claimed in Claim 2, in which there are provided openings through the tube wall, in the downstream half of its length, upstream from the transverse blocking piece.

4. A silencer as claimed in Claim 3, in which the openings out of the tube are arranged in a cluster upstream of the last downstream turn of the vane.

•'S'.^ 0 \ A silencer as claimed in any one of the preceding claims, in ,. "3, "

■•I which the inlet opening is provided by an inlet connection which is

C26PM*98r/;funnel-shaped and which diverges in a downstream direction and connects with one end of the cylindrical shell.;6. A silencer as claimed in Claim 5, in which the outlet opening is provided by an outlet connection which is funnel-shaped and which connects with the opposite end of the cylindrical shell and which converges in a downstream direction from the cylindrical shell.;7. A silencer as claimed in any one of the preceding claims, in which there is provided a casing around the cylindrical shell, a sound-insulating cavity being defined between the cylindrical shell and the casing.;

8. A silencer as claimed in Claim 7, in which the cylindrical shell is foraminous.;

9. A silencer as claimed in any one of the preceding claims, in which the vane has a wrinkled surface.;

10. A silencer as claimed in any one of the preceding claims, in which the vane is made up of a pair of axially spaced upstream and downstream helical vane flights forming a vane having a sound-insulating helical cavity defined between the vane flights.;

11. A silencer as claimed in Claim 10, in which the upstream vane flight is foraminous.;

12. A method of making a shell and core assembly for an silencer as claimed in Claim 1, which includes;* 3 if '16FEBW7 exhaust__^_ -16- 210804 V. forming the core by wrapping a helical vane worm-screw fashion around a central axial support, and securing the vane thereto; partly forming the cylindrical shell from sheet metal material to have overlapping longitudinal edges for making a longitudinal seam; sliding the core with little radial clearance longitudinally into the thus partly-formed cylindrical shell; pressing the overlapping longitudinal edges of the shell together to form a longitudinal seam, thereby taking up the radial clearance; and bending the seam over to lie flat against the cylindrical shell, the sheet metal material thereby being drawn tightly around the core, and being placed under circumferential tension, the core being gripped frictionally and having a radial interference fit with the shell and being located axially in position within the shell. •

13. A method as claimed in Claim 12 which includes the step, before bending over of the seam, of screwing the assembly onto a helical mandrel to serve as a platen or anvil on the inside of the seam for the bending over of the seam.

14. A method as claimed in Claim 13 in which the bending over of the seam takes place by a platen of a press.

15. A method as claimed in Claim 13 in which the bending over of the seam takes place by a manually or machine operated hammer.

16. A method as claimed in any one of the Claims 12 to 15 o'inclusive, which includes the step of spot-welding the pressed 6FEBt987 210394 overlapping longitudinal edges of the formed seam together at longitudinally spaced intervals, before bending the seam over to lie flat against the cylindrical shell.

Claim 9, which includes wrinkling a sheet metal strip having a width and a length corresponding to the radial length and overall length of the vane; wrapping the wrinkled strip edge-on worm-screw fashion around a central axial support; and securing the inner edge of the helical worm thus formed to the central axial support.

18. An exhaust silencer, substantially as described and illustrated herein.

19. A method of making an exhaust silencer, substantially as described and illustrated herein.

20. The core of a silencer when made in accordance with the method as claimed in Claim 17.

21. A core assembly when made in accordance with the method as claimed in anyone of the Claims 12 to 15 inclusive.

22. A helical mandrel shaped and dimensioned to screw into a shell and core assembly as claimed in Claim 21. 17 A method of making the core for the silencer as claimed in -18- f> 210394

23. A helical, mandrel substantially as described and illustrated herein.

24. A core assembly substantially as described and illustrated herein. PlAcRn/€A)^€^-8y -his/their authorised Agents A. J. PARK & SON, PER -.ID> . it 6 FEB 1987 o;fr r4-