NZ203943A - Silencer having an outer shell free of lingitudinal creasing and with baffle to body joints free of welding - Google Patents

Description

20394S f 19 APR 1984 , —* ;|j& RECEIVED ;Patents Form No. 5 ;Number 203,943 ;PATENTS ACT 1953 ;Dated April 19, 1983 ;COMPLETE SPECIFICATION ;A SILENCER AND METHOD OF FORMING SAME ;I/m RONALD MALCOLM BOND SANDERSON, a New Zealand citizen of 51 Victoria Street, Petone, New Zealand do hereby declare the invention for which I/kk pray that a Patent may be granted to me/tiX, and the method by which it is to be performed, to be particularly described in and by the following statement: ;- 1 - (followed by page 1a) ;20*943 The present invention relates to a method of forming a silencer for an exhaust system, such as, for example, the exhaust system of an internal combustion engine.

Such exhaust systems are generally composed of steel exhaust piping and usually include one or more silencers connected thereto at various points. A silencer generally comprises a hollow body portion housing sound deadening means, and having a "nose" in the form of a short section of reduced diameter piping at its each end, whereby the silencer may be connected into the exhaust system. Various constructions of silencer are known in the art and the present invention is concerned with one type in which the body portion of the silencer comprises a longitudinally extending hollow cylinder, formed by, for example, a section of piping, which is closed at each end, where it is also provided with reduced diameter nose portions to enable the silencer to be connected to an exhaust system. The body portion of the silencer houses a baffle, in the form of a perforated section of piping, which extends longitudinally within the silencer with its ends protruding from the ends of the silencer body portion, to form the said reduced diameter nose portions. Adjacent the protruding nose portions 2 the piping comprising the outer shell of the silencer body portion is generally welded or similarly secured to the exterior of the protruding ends of the baffle.

The manufacture of silencers of this type involves time consuming welding to be performed at each end of the silencer between the silencer body portion and the protruding ends of the baffle, and, additionally, the resulting welded seams are prone to corrosion and to fracture as a result of vibration to which silencers are often exposed in use.

Accordingly it is an object of the present invention to provide an improved method forming a silencer of the type described wherein such welding or similar seam joining is not required to be performed at each end of the silencer and thus also to provide a silencer which in its finished form is free of welded or similarly jointed body portion to baffle seams at its ends.

In its first aspect the present invention provides a method of forming a silencer having a body portion and two nose portions from a continuous section of piping (as herein defined) of a substantially constant diameter, the method 3 S03943 comprising the steps of: providing a continuous section of piping of substantially constant diameter, providing a longitudinally extending perforated hollow baffle, positioning the said baffle within the interior of the said section of piping, and forming each end of the said piping into a nose portion of reduced diameter with the junction of the said body portion with each of the said nose portions as an intermediate tapered portion substantially free of longitudinal creasing and such that within each said nose portion the respective end of the said baffle is gripped in position to secure said baffle and without significant deformation thereof, by compressing each respective end of said piping into an internally tapered die.

In its second aspect the present invention provides a silencer comprising a body portion that has been formed from a continuous section of piping of a substantially constant diameter, said body portion housing a longitudinally extending perforated hollow baffle extending longitudinally within the said body portion and comprising nose portions one at each end of the said body portion 4 203943 with each end of the said baffle gripped in position within its adjacent nose portion without significant deformation of the baffle, the junction of the said body portion with each said nose portion comprising an intermediate tapered portion substantially free of longitudinal creasing.

In this specification the term piping is intended to encompass both round and square or rectangular cross-section piping as well as other suitable shapes, as it will be appreciated that the invention could be performed with piping of almost any type.

In one known form of silencer the end pipes whereby the silencer is fixed into an exhaust system are connected to the silencer body by collapsing of the ends of the silencer body about the end pipes, by forcing a split cavity mould over the ends of the silencer body. Because the mould is a split cavity mould longitudinal creases are formed at the ends of the silencer body, which is undesirable. In addition the silencer to end pipe joint strength is often less than satisfactory so that welding is frequently required in any event. With the present invention the outer shell of the silencer is formed so as to 203943 be substantially free of longitudinal creasing and by a different technique and a more reliable baffle to silencer body joint is formed so that the requirement for welding or similar securing or seam joining at the ends of the silencer is eliminated. A much more robust silencer can therefore be formed, and can be formed more speedily than would otherwise be the case.

Further description of preferred forms of the invention is given with reference to the accompanying drawings, in which: Fig. 1 is a side view of a silencer in accordance with the invention and formed in accordance with the method of the invention, with a portion thereof shown in cutaway cross-section and in phantom outline, and Fig. 2 is a schematic cross-sectional side view of an internally tapered die suitable for forming silencers in accordance with the method of the invention, and ^ Fig. 3 is a perspective view of an apparatus suitable for forming silencers of the invention in accordance with the method of the invention, a partially completed silencer being shown positioned on the apparatus, and Pig. 4 is a plan view of one end of the apparatus of Fig. 3.

The silencer shown in Fig. 1 comprises an outer shell generally indicated at 1 and a longitudinally extending perforated hollow baffle 2, both of which are cylindrical in cross-section. The outer shell 1 of the silencer comprises a body portion 1a, which is of a diameter greater than the diameter of exhaust piping to which the silencer is intended to be connected, and nose portions 1b, which are of a reduced diameter, substantially the same diameter as the diameter of the said exhaust piping (they may be a little larger or a little smaller to allow for connection of the exhaust piping into or over each nose portion at either end of the silencer). In the silencer shown the junction of the body portion 1a with each of the nose portions lb comprises an intermediate tapered portion 1c which extends between the body portion 1a and the nose portions 1b, at either end of the silencer. The diameter of 7 203943 each intermediate tapered portion 1c reduces from the diameter of the body portion 1a to the diameter of its adjacent nose portion 1b.

The baffle 2 extends within the interior of the silencer from one end to the other and sound deadening material (not shown in the drawings) is preferably positioned within the space 3 between the baffle 2 and the body portion 1a of the silencer shell 1. This sound deadening material may be loosely wrapped around the baffle 2. Each end 2a of the baffle 2 is gripped in position within its adjacent nose portion 1b, at either end of the silencer. In manufacture of the silencer in accordance with the method of the invention, a section of piping of the same diameter as that intended for the body portion 1a is provided and is collapsed or formed to a reduced diameter so as to be a tight fit about the ends of the baffle 2, to secure it in position and to form the nose portions 1b. The end of the said piping may be formed to a reduced diameter by, for example, compressing into an internally tapered die such as that illustrated in Fig. 2, which will be referred to later. The ends of the piping are formed from the shape shown in phantom outline at 4 in Fig. 1 so that nose and OFFfCE ln termediate tapered postions 1b and 1c are formed ■ i...\ noo :F'iV ' > 8 on its end, with the end 2a of the baffle gripped inside the nose portion. Preferably the ends of the piping are collapsed sufficiently about the ends 2a of the baffle 2 that these ends are themselves collapsed slightly also, say to 1/8" reduced diameter. However lesser amounts of collapse can be employed so long as the ends of the baffle 2 are securely gripped in position.

An apparatus suitable for so forming silencers in accordance with the method of the invention is shown in Figs. 3 and 4. The apparatus comprises a flat bed 5 having support legs 6. An internally tapered die 7, of the type shown in cross-section in Fig. 2, is provided at one end of the bed 5 (shown particularly in Fig 4.) and a hydraulic ram generally indicated at 8 at the other.

Strengthening rods 9 extend longitudinally of the apparatus between end plates 10 as shown. The hydraulic ram 8 comprises a movable ram head 11 supported by plate 12 which is reciprocally slidably movable on the two lower rods 9, and a column 13. The ram head 11 can move back and forth along the bed 5 of the apparatus on the lower rods 9 in the direction indicated by arrows A and B. The die 7 is fixedly mounted in its end plate 10 and a pair of l=|paced work supports 14, which extend laterally of 9 2U3943 the apparatus between the two lower rods 9 are fixedly positioned as shown.

In use of the apparatus, to form a silencer in accordance with the method of the invention, the said continuous section of piping from which the silencer shell is formed is placed on the work supports 14 in the position of the partly completed silencer 15 shown. The outer shell of the silencer is indicated at 15a. The baffle referred to earlier, preferably having sound deadening material wrapped around it, is positioned within the piping 15a as indicated at 15b, and the hydraulic ram 8 is operated so that the ram head 11 is caused to move in the direction of arrow A, to abut the proximal end of the piping 15a and the baffle 15b, and move them towards and compress them into the die 7 so that their distal ends will enter the die 7 and be formed to the finished shape shown in Fig. 1, and so that the end of the baffle 2 will be gripped in position as earlier described. The ram 8 is then operated so that the ram head 11 is caused to return in the direction of arrow B and the partly formed silencer removed from the die 7. The silencer is then reversed in position so that its one formed end abuts the ram head 11 and the ram 8 is again operated so that the other end of the silencer will 203943 compress into the die 7 to be formed thereby in a similar manner.

The die 7 is shown in more detail in cross-section in Fig. 2 and it comprises a die mouth 16, a first internal portion 17 which is tapered as shown, and a second internal portion 18 of substantially constant diameter. The internal portion 17 reduces in diameter from at least the diameter of the piping to be formed in the die, at the die mouth, to the reduced diameter to which it is desired to form the silencer nose portion. The angle of taper is typically 10-15° from the While each end of a silencer could be formed with one compression into the die, it may also be convenient, particularly with relatively thick walled piping, to form each end with two separate compression operations, a first one into a die with a 10° taper, to reduce the diameter of the end of the piping from, say, 3" to 2", and a second one into a die with a 15° taper, to further reduce the diameter of the end of the piping to 1-3/4". horizontal. shown positioned within the die.

A plunger 19 may be provided within the 203943 1 1 interior of the die 7, reciprocally movable therein under the influence of a small hydraulic ram 20, as is known in the art. The ram 20 can then be operated to push the plunger 19 into the die 7 in the direction of arrow C in Fig. 2, to assist in removing the formed end of silencers from the die.

It will be appreciated that on the provision of appropriately shaped dies, the method of the invention could be used to form silencers from, for example, square piping, as well as the round piping shown.

The foregoing describes my invention including preferred forms thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope thereof, as defined in the following claims.

Claims (1)

1. 203.943 1. A method of forming a silencer having a body portion and two nose portions from a continuous section of piping (as herein defined) of a substantially constant diameter, the method comprising the steps of: providing a continuous section of piping of substantially constant diameter, providing a longitudinally extending perforated hollow baffle, positioning the said baffle within the interior of the said section of piping, and forming each end of the said piping into a nose portion of reduced diameter with the junction of the said body portion with each of the said nose portions as an intermediate tapered portion substantially free of longitudinal creasing and such that within each said nose portion the respective end of the said baffle is gripped in position to secure said baffle and without significant deformation thereof, by compressing each respective end of said piping into an internally tapered die. 2. A method as claimed in claim 1, wherein the interior of the said internally tapered die 12 WHAT I CLAIM IS: 13 203943 comprises a die mouth, a first internal portion which is tapered and the diameter of which reduces from at least the diameter of the said piping at the die mouth to substantially said reduced diameter, and a second internal portion of a substantially constant diameter. 3. A method as claimed in claim 2, wherein the said first internal portion of the die has an internal taper of 10-15°. 2, wherein the said compressing of each respective end of the said piping into an internally tapered die comprises a two step operation in which said piping is compressed into a die having an internal taper of a first angle and is compressed subsequently into a die having an internal taper of a second angle which is greater than said first angle. 5. A method as claimed in claim 4, wherein said first angle is substantially 10° and said second angle is substantially 15°. 4. A method as claimed in either of claims 1 jaif 6. A silencer comprising a body portion that has been formed from a continuous section of piping of a substantially constant diameter, said body 14 203443 portion housing a longitudinally extending perforated hollow baffle extending longitudinally within the said body portion and comprising nose portions one at each end of the said body portion with each end of the said baffle gripped in position within its adjacent nose portion without significant deformation of the baffle, the junction of the said body portion with,each said nose portion comprising an intermediate tapered portion substantially free of longitudinal creasing. 7. A method of forming a silencer substantially as herein described with reference to the accompanying drawings. 8. A silencer substantially as described herein and as illustrated in Fig. 1 of the accompanying drawings. WEST-WALKER, McCABE ATTORNEYS FOR THE APPLICANT ."J.?:. I'ATENTOFFICE 18 i\AR 1986 RECEIVED -• v., .. ' .-.I'--"