Method for forming a collar in a muffler housing

Abstract

Method for forming a collar in a muffler shell including: providing a muffler shell made of a metal sheet and forming a muffler housing, the muffler shell having an exhaust gas opening, providing a collar forming head having a rotational axis and at least two movable expanders, introducing a collar forming head into a muffler housing, moving the expanders of the collar forming head introduced into the muffler shell radially away from the rotational axis of the collar forming head from a retracted position to an expanded position rotating the collar forming head around the of the collar forming head, bringing the rotating expanded collar forming head in contact with the metal sheet forming an outwardly projecting collar around the exhaust gas opening by flaring the edge of the metal sheet.

Claims

1. A method for forming a collar in a muffler shell for a muffler for an internal combustion engine, the method comprising: providing a muffler shell made of a metal sheet and forming a muffler housing, the muffler shell having an exhaust gas opening, providing a collar forming head having a rotational axis and at least two movable expanders, introducing the collar forming head into the muffler housing, wherein the expanders are in a retracted position, by moving the retracted collar forming head along the rotational axis through the exhaust gas opening in the muffler shell, wherein the retracted collar forming head has a largest diameter smaller than the largest diameter of the exhaust gas opening in the muffler shell, moving the expanders of the collar forming head introduced into the muffler housing radially away from the rotational axis of the collar forming head from the retracted position to an expanded position, in which the largest diameter of the expanded collar forming head radially to the rotational axis is larger than the largest diameter of the exhaust gas opening, rotating the collar forming head around the rotational axis of the collar forming head, bringing the rotating expanded collar forming head in contact with the metal sheet adjacent to and surrounding the exhaust gas opening in the muffler shell by moving the expanded collar forming head along the rotational axis in a direction outwardly from the interior of the muffler housing, forming an outwardly projecting collar around the exhaust gas opening by flaring the edge of the metal sheet surrounding the exhaust gas opening outwardly and increasing the size of the exhaust gas opening by moving the expanded collar forming head along the rotational axis in a direction outwardly from the interior of the muffler housing to the exterior of the muffler housing, and inserting muffler interior components into the muffler housing prior to the step of forming the outwardly projecting collar.

2. The method according to claim 1, wherein the step of forming the outwardly projecting collar is performed in one step.

3. The method according to claim 1, wherein the method comprises the step of inserting an internal pipe into the muffler housing through the outwardly projecting collar.

4. The method according to claim 3, wherein forming the outwardly projecting collar around the exhaust gas opening comprises the formation of a collar wall, and wherein after the step of inserting the internal pipe, the internal pipe is expanded to contact the collar wall.

5. The method according to claim 3, wherein the method comprises the step of inserting an external pipe into the internal pipe through the outwardly projecting collar.

6. The method according to claim 1, wherein the step of providing a muffler shell comprises forming a rolled envelope muffler housing from the muffler shell.

7. The method according to claim 1, wherein the step of providing a muffler shell comprises providing two muffler shell halves for forming a muffler housing from the two muffler shell halves, and wherein the exhaust gas opening is provided in at least one of the two muffler shell halves.

8. The method according to claim 1, wherein the step of providing a muffler shell comprises providing at least one flat metal sheet comprising the exhaust gas opening, and rolling the at least one flat metal sheet to form the muffler housing or deep drawing the at least one flat metal sheet to form at least one of two muffler shell halves.

9. The method according to claim 1, wherein the step of providing a muffler shell comprises providing two flat metal sheets and deep drawing the two flat metal sheets to form two muffler shell halves and forming the exhaust gas opening during the deep drawing step in at least one of the two muffler shell halves.

10. The method according to claim 1, wherein the step of providing a muffler shell comprises providing at least one flat metal sheet, rolling the at least one flat metal sheet to form the muffler housing or deep drawing the at least one flat metal sheet to form at least one of two muffler shell halves, and subsequent to the rolling or deep drawing step forming the exhaust gas opening.

11. The method according to claim 1, wherein the step of providing a muffler shell comprises providing a muffler shell with an elongated exhaust gas opening adapted to form an outwardly projecting collar having a planar mouth in a direction radial to the rotational axis of the collar forming head.

12. A muffler obtained by the method according to claim 1.

13. A vehicle comprising a muffler according to claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is further described with regard to embodiments, which are illustrated by means of the following drawings, wherein:

(2) FIG. 1 is a side elevational view of an embodiment of the collar forming apparatus for performing the method according to the present invention;

(3) FIG. 2 is a fragmentary elevational view of the collar forming apparatus of FIG. 1, showing in broken lines the retracted and expanded collar forming positions of the flange forming members and showing in unbroken lines the flange forming members in their expanded collar forming positions withdrawn from the muffler shell;

(4) FIGS. 3a to 3h show the steps of the method for forming a collar in the muffler housing according to one embodiment of the inventive method.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) Referring to the drawing, the collar forming apparatus of the present invention, indicated generally at 10, is shown in FIG. 1 in a position immediately subsequent to the formation of a collar or neck 12 around an exhaust gas opening 14 in the metal sheet 16 of a muffler shell 18. The collar forming apparatus 10 includes a frame 20 having a base 22 to which upright support columns 24 (one shown) are secured. A pair of vertically spaced apart tables 26 and 28 is slidably mounted to the support columns 24 for movement relative to the base 22 and for movement relative to each other. A hydraulic cylinder 30 is interposed between the base 22 and the lower table 28 and is operable to raise and lower the table 28. A vertical displacement actuator 32 having a rod 34 connects the upper table 26 with the lower table 28 in an adjusted fixed position so that operation of the hydraulic cylinder 30 causes simultaneous movement of the tables 26 and 28, while operation of the vertical displacement actuator 32 causes relative vertical movement between the upper table 26 and the lower table 28.

(6) Clamping the muffler housing may be done with a flexible member 36 secured to the underside of the lower table 28 and wrapping around the muffler shell 18 holding it firmly against support feet 38 secured to the underside of the table 28. The vertical adjustable movement of the table 28 allows the collar forming apparatus 10 to accommodate exhaust gas openings in muffler shells having a variety of diameters. Any other method for holding the muffler is however applicable.

(7) The upper table 26 carries a drive 40 which extends through the lower table 28 for vertical movement relative thereto and to which drive 40 is secured a collar forming head 42. Expanders 44 which form the collar during operation are mounted to the collar forming head 42 and are operable to engage the metal surrounding the exhaust gas opening 14, thereby varying the diameter of the collar forming head 42. When rotated by the drive 40 about an upright rotational axis 46 of the collar forming head 42 while being withdrawn from the exhaust gas opening 14 along an axial path from the inside of the muffler shell to the outside of the muffler shell, the expanders 44 work the metal to form the collar 12. The movement of the collar forming head 42 along the rotational axis 46 is achieved by operation of the vertical displacement actuator 32 which causes the upper table 26 to move up and down relative to the table 28 so as to move the collar forming head 42 and the expanders 44 up and down.

(8) The collar forming head 42 carries symmetrically arranged expanders 44. The expanders are movable and are configured to vary the diameter of the collar forming head 42 in a radial direction relative to the rotational axis 46.

(9) The expanders 44 may be displaced to their expanded collar forming positions or to their retracted positions, thereby varying the diameter of the collar forming head. The movement of the expanders is shown by the arrows in FIG. 2.

(10) As shown in FIG. 2, each expander 44 has a longitudinal axis and includes a working surface 98 from which side walls extend transversely. A longitudinal groove 104 is formed in each expander 44 to receive a rectangular mounting portion 106 of the support member 62, with the expander 44 being secured to the support member 62 in a suitable manner. Accordingly, a variety of sizes and shapes of the expanders 44 can be interchangeably mounted to the support members 62 to fit the hole size, the metal sheet thickness, and the composition of the muffler shell 18.

(11) In operation, the muffler shell 18 is clamped against the feet 38 by the clamp 36. The expanders 44 are in their retracted positions as shown in broken lines in the right hand side of FIG. 2. The vertical displacement actuator 32 is then operated to lower the upper table 26 relative to the lower table 28 in order to lower the collar forming head 42 to insert the retracted expanders 44 through the exhaust gas opening 14 into the inner space (interior) of the muffler shell 18. Next, the expanders 44 are moved to their expanded collar forming positions, as shown in broken lines on the left hand side of FIG. 2 where they come to lie under the portions of the metal sheet 16 surrounding the exhaust gas opening 14.

(12) The collar 12 is then formed by working the metal surrounding the exhaust gas opening 14. This working of the metal is performed by actuating the drive 40 which rotates the collar forming head 42 about the axis 46 thereby rotating the expanders 44. The vertical displacement actuator 32 is then actuated to raise the upper table 26 thus withdrawing the rotating expanders 44 from the exhaust gas opening 14. During this process, the rotating expanders 44 work the metal surrounding the exhaust gas opening 14 to form the upstanding collar 12 and are held in their (expanded) collar forming positions. As shown in unbroken lines in FIG. 2, the expanders 44 are shown in a position in which the collar forming procedure is essentially complete. Thereafter, the muffler shell 18 is indexed to another position for the next process step.

(13) Another muffler shell may then be secured to the underside of the table 28 with the exhaust gas opening in the metal sheet of the muffler shell positioned in alignment with the collar forming head 42.

(14) FIGS. 3a to 3h show the various steps of the muffler manufacturing according to one embodiment of the present invention for a rolled muffler 100. Shown in FIG. 3a, a flat sheet of metal 16 with an exhaust gas opening 11 is provided. The exhaust gas opening 11 has an elongated shape adapted to form an outwardly projecting collar having a planar mouth in a direction radial to the rotational axis of the collar forming head 42 once the collar 12 is formed. The flat metal sheet 16 is then rolled in order to form the rolled envelope 110 (muffler housing) of the muffler as shown in FIG. 3b. The rolled envelope 110 has the exhaust gas opening 11 at a location where the curvature radius of the muffler housing is low.

(15) In the next step shown in FIG. 3c, the stuffing of the muffler interior components 120 into muffler shell 110 (muffler housing) is performed, and subsequently the step of end capping the muffler, i.e. providing the rolled envelope 110 (muffler housing) with end caps 140 thereby closing the muffler are performed, as shown in FIG. 3d. The muffler housing 110 provided with the end caps 140 now has maximal stability for reduced distortion during the collar forming step.

(16) Subsequently, as shown in FIG. 3e, the outwardly projecting collar 12 is formed by the method as described in detail hereinbefore. In particular, a collar forming head 42 is introduced into the interior space of the rolled envelope 110 with the expanders 44 being in a retracted position (retracted collar forming head 42), by moving the retracted collar forming head 42 along the rotational axis 46 of the collar forming head 42 through the exhaust gas opening 11 in the muffler shell 18. The expanders 44 of the collar forming head are then moved radially away from the rotational axis 46 of the collar forming head 42 from the retracted position to the expanded position (expanded collar forming head 42). While rotating the expanded collar forming head 42 around the rotational axis 46 of the collar forming head 42, the rotating expanded collar forming head 42 is brought in contact with the metal sheet 16 adjacent to and surrounding the exhaust gas opening 11 in the rolled envelope 110 by moving the expanded collar forming head 42 along the rotational axis 46 in a direction outwardly from the interior of the rolled envelope 110 and thus forming an outwardly projecting collar 12 around the exhaust gas opening 11 by flaring the edge of the metal sheet 16 surrounding the exhaust gas opening 11 outwardly and increasing the size of the exhaust gas opening 11 by moving the expanded collar forming head 42 along the rotational axis 46. Forming the outwardly projecting collar 12 is performed in one step, thereby forming the collar 12 without the need of repeating the collar forming step.

(17) As can be best seen from FIG. 3e and particularly in the zoomed representation of the collar, the elongated exhaust gas opening 11 has a shape adapted to form an outwardly projecting collar 12 having a planar mouth.

(18) Subsequent to forming the outwardly projecting collar 12, an internal pipe 20 is introduced into the muffler through the outwardly projecting collar 12. As can be seen from FIG. 3f and particularly in the zoomed representation of the collar, the internal pipe 20 slightly protrudes from the collar mouth over about 1 mm length. The internal pipe 20 may be joined to the muffler interior 120 by mechanical lock or press fit (fastening between the two parts which is achieved by friction after the parts are joined together). After the internal pipe 20 has been introduced into the muffler, the internal pipe 20 is slightly expanded to touch the wall 13 of the outwardly projecting collar 12 in the calibration step to ensure connection between the collar 12 and the internal pipe 20.

(19) Finally, an external pipe 22 is introduced over about 1 cm into the internal pipe of the muffler as shown in FIG. 3g and particularly in the zoomed representation of the collar with the external pipe 22 and the internal pipe 20. Subsequently, the external pipe 22 is welded to the outwardly projecting collar 12. The weld 23 also joins the protruding part of the internal pipe 20 to the collar 12 and to the external pipe 22 as can be seen best from FIG. 3h which is a zoomed representation of the collar with the external pipe 22 and the internal pipe 20.

(20) From the above description, it can be seen that an improved collar forming method is provided for forming collars in muffler housings having a variety of metal sheet thicknesses, exhaust gas openings and material compositions, irrespective of the stuffing of the muffler. The expanders are configured to allow a variety of collar forming head diameters, thereby allowing flexible use for the collar forming head for any kind of muffler having a wide variety of collar diameters and lengths, thus providing for an enhanced versatility of the method. Additionally, the method allows for collar formation in muffler half shells of half-shell type mufflers.