US3242558A

US3242558A - Method of making intermediate shell construction for silencer or muffler

Info

Publication number: US3242558A
Application number: US202143A
Authority: US
Inventors: James H Selig
Original assignee: OLDBERG Manufacturing CO
Current assignee: APX GROUP Inc; OLDBERG Manufacturing CO
Priority date: 1962-06-13
Filing date: 1962-06-13
Publication date: 1966-03-29
Anticipated expiration: 1983-03-29

Description

March 29, 1966 J. H. sELlG METHOD OF MAKING INTERMEDIATE SHELL CONSTRUCTION FOR SILENCER OR MUFFLER 4 Sheets-Sheet 2 Filed June l5, 1962 IN VENTOR: JAMES H. SEL la.

March 29, 1966 J, H, SELIG 3,242,558

METHOD OF MAKING INTERMEDIATE SHELL CONSTRUCTION FOR SILENOER OR MUFFLER Filed June 1.3, 1962 4 Sheets-Sheet 5 IN VEN TOR: JAMES H. SEL m.

TIE -7- MQW March 29, 1966 J. H. SELIG METHOD OF MAKING INTERMEDIATE SHELL CONSTRUCTION FOR SILENCER OR MUFFLER Filed June 13, 1962 4 Sheets-Sheet 4, v

United States Patent O METHOD OF MAKING INTERMEDIATE SHELL CONSTRUCTION FOR SILENCER OR MUFFLER James H. Selig, Grand Haven, Mich., assignor to Oldberg Manufacturing Company, Grand Haven, Mich., a corporation of Michigan Filed June 13, 1962, Ser. No. 202,143 7 Claims. (Cl. 29-157) This invention relates t-o a method of making an intermediate shell construction for a mufller or silencer of la character particularly adaptable for silencing or attenuating sound waves entrained in exhaust gas streams of internal combustible engines and more especially to an intermediate shell and gas pass-age tube construction or unit for use in a mufer or silencer.

It has been a general practice in conventional types of muffler or silencer to provide one or more gas passage tubes wherein the gas passage tube is surrounded or embraced by lan imperforate cylindrically-shaped shell, termed an intermediate shell, for the pur-pose of providing s-ound attenuating chambers or compartments for attenuating or d-amping sound waves of comparatively high frequencies in an exhaust gas stream. A plurality of such chambers is usually provided between the intermediate shell and the gas passage tube wall by a plurality of annular rings or partition members spaced lengthwise of the shell, the space between each pa-ir of `annular members denng a high frequency sound attenuating chamber.

Communication between the gas passage tube and adjacent high frequency sound attenuating chambers is attained through a comparatively large number of small openings in the gas passage tube wall in order to attenuate high frequency sound waves. Intermediate shell and gas passage tube constructions of this character have been expensive to produce due to the number of rings required and the diiculties of spacing the rings to secure sound. attenuating chambers of proper lengths. It has been a usual practice to weld the annular members or rings to the gas passage tube and then insert the assemblage of tube and rings within -an intermedia-te shell. In some instances, annular anges -on the rings are welded to the intermediate shell. In constructions where the annular members are not securely held in position, vibration and varying gas pressures may cause noise.

The present invention embra-ces a novel method of assembling a gas passage tube member and intermediate shell member construction for a muiiler wherein partition means between the tube member and the shell member are integrally formed on one of said members thereby eliminating the use of annular members between the gas passage member and the 'intermediate shell member.

Another object of the invention `resides in a method of forming `transversely extending partition portions from one of said members by distorting the metal of the member in a manner whereby =a plurality of annular chambers of `desired length are formed between the members by the integral partition portions.

Another object of the invention resides in the method of fashioning a perforated gas passage tube and a surrounding shell to form a plurality of high frequency sound attenuating chambers wherein transversely extending integral portions of the shell member are formed by a 4series of progressive steps of distorting the metal of the shell to form annular partitions or walls which engage the gas passage tube to define annularly-shaped sound attenuating chambers.

Another object of the invention resides in a method `of forming and assembling a gas passage tube and intermediate shell tube unit wherein spaced circular regions of the intermediate shell tube are distorted and forced inwardly in engagement with the gas passage tube disposed in telescoped relation with the intermediate shell tube.

Another object of the invention is the provision of a method of forming transversely extending integral circular flanges on a metal tube involving the steps of `distorting the metal of the tube laterally by transversely applied forces and subsequently applying pressure lengthwise of the tube to progressively further distort the metal transversely and compress the distorted metal upon itself to form a partition substantially equal to twice the wall thickness yof the tube.

Another object of the invention resides in a method of form-ing an intermedi-ate shell unit for a mufer construction wherein portions of the intermediate shell wall are processed in a manner whereby transversely exten-ding portions are progressively formed by pressure lapplied lengthwise of the shell.

Further objects and `advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to econ-omies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIGURE 1 is Ia longitudinal sectional view of Ia sound attenuating muffler embodying a form of intermediate shell and gas passage tube construction of the invention;

FIGURE 2 is a transverse sectional view taken substantially on the line 2-2 of FIGURE l;

FIGURE -3 is an elevational View of an intermedi-ate shell illustrating one of the method steps in fashioning the shell and gas passage units;

FIGURE 4 is a View illustrating an assembly of gas passage tube member and intermediate shell member preparatory to `a subsequent step 'in the meth-od of forming the unit;

FIGURE 5 is a view similar to FIGURE 4 illustrating the step in the method of completing the inter-mediate shell and gas passage unit;

FIGURE 6 is an enlarged fragmentary sectional view illustrating the partitions formed on the intermediate shell defining the high frequency sound attenuating chambers in the unit construction;

FIGURE 7 is a transverse sectional View taken substantially on the line 7 7 of FIGURE 6;

FIGURE 8 is a semi-schematic view illustrating a method of deepening the -grooves in the intermediate shell in a form of construction wherein the gas passage tube is of reduced diameter;

FIGURE 9 is a fragmentary detail view illustrating the configuration of a groove in an intermediate shell upon completion of the method step shown in FIGURE 8;

FIGURE 10 is a view showing a modied method of providing inwardly extending partitions on the intermediate shell;

FIGURE 1l is a transverse sectional view taken substantially on the line 11-11 of FIGURE l0;

FIGURE l2 is a View similar to FIGURE l0 showing a method step of forcing the partition portion inwardly into engagement with the gas passage tube, and

FIGURE 13 is a sectional view illustrating a method of forming transversely extending partitions on the gas passage tube.

While the unit construction and method of making the same have particular utility as a sound attenuating component in a silencer or muiiler for attenuating sound waves entrained in exhaust gas streams from internal combustion engines, it is to be understood that the method of the invention of assembling cylindrically-shaped members may be employed wherever the invention may be found to have utility.

One form of sound attenuating unit of the invention is illustrated in FIGURES 1 and 2 embodied in a muffler or silencer for use with an exhaust gas stream of an internal combustion engine. Referring to FIGURES 1 and 2, the muffler is inclusive of a main or outer shell, casing or housing 12 which, as shown in FIGURE 2, is of generally oval shape. The muffler may be of other shape if desired. The shell or casing 12 illustrated is of the double wall type having an outer layer of metal 14 and an inner layer of metal 15 which are slightlyseparated to provide a space 17 to reduce shell noise.

In certain installations it may be desirable to fill the space 17 with asbestos, mineral fibers or other high temperature resistant insulation. The shell or casing construction is provided with end walls, heads or

closures

18 and 19, each of the heads or closures being formed with a peripheral flange configuration 20 of generally U-shaped cross-section providing a peripheral recess or groove which receives the mating or contiguous end regions of the shell walls 14 and 15 in the manner shown in FIGURE 1.

The

flanges

22 and 23 of the U-sha-ped configuration 20 may be rolled or crimped into engagement with the vends of the shell walls 14 and 15 to form a huid-tight joint. The end wall 18 at the inlet end of the muffler is fashioned with an opening defined by a circular ange 24, the opening accommodating a coupling sleeve or tubular tting'26 which is preferably welded or otherwise secured to the flange 24.

The portion of the coupling sleeve exteriorly of the end head 18 is arranged to accommodate an exhaust inlet tube or exhaust pipe 28 adapted to convey exhaust gases from an internal combustion engine into the muffler construction.

v The end head 19 at the exhaust outlet end of the muier is provided with an opening defined by a circular flange 30 which accommodates a coupling sleeve or tubular fitting 31 welded or otherwise secured to the flange 30. The coupling 31 is adapted to be connected with a tailpipe (not shown) or other'tubular means for conveying away exhaust gases from the mufer.

Disposed within the muffler housing 12 are transversely spaced partitions or

headers

34, 35 and 36, the headers or partitions being provided with openings to receive

gas passage tubes

38 and 40, the tube 40 being a gas outlet tube connected with the outlet coupling 31, as shown in FIGURE 1. One or more of the headers may be provided with openings 42, shown in FIGURE 2, to facilitate passage of gas through the muflier in addition to the

tubes

38 and 40.

The muier shown in FIGURES 1 and 2 embodies a gas passage and sound attenuating unit construction 44 of the invention. The construction 44 includes a tubular member 46, herein referred to as an intermediate shell, and a gas passage tube 48 of lesser diameter than the intermediate shell 46 arranged in telescoped relation therewith. In the embodiment illustrated, the inlet end of tube 48 is in telescoping relation with the inlet fitting 26 and `forms a gas inlet passage tube for conveying exhaust gases into the muffler through substantially the length thereof.

The peripheral wall of the gas passage tube or member 48 is provided with a comparatively large number of small openings or orifices 50.

The intermediate shell or member 46 is integrally formed with interiorly extending

portions

52, 54, 56 and 58 which engage the exterior surface of the gas passage tube or member 48 and provide therewith annularly shaped high frequency sound

wave attenuating chambers

62, 64 and 66. The openings 50, in the Wall of the gas passage tube 48, provide acoustic couplings with the

chambers

62, 64 and 66 for attenuating sound waves of comparatively high frequency. The method of forming the sound attenuating unit 44 will be hereinafter described in detail.

The

gas passage tubes

38 and 40 may also be perforated or fashioned with small openings in the walls thereof in various areas, if desired, `for gas transfer purposes as well 4 as sound attenuating purposes. The header or partition 34 forms with the inlet head 18 a chamber 70 which is 1n communication with the

gas passage tubes

38 and 40. The

end head 19 forms with the header or partition 36 a Y chamber 72 which is in communication with the opposite ends of the

gas passage tubes

38 and 48. The

chambers

70 and 72 provide for the transverse flow of exhaust gases and form resonance chambers for attenuating low frequency sound waves.

In the arrangement shown in FIGURES 1 and 2, the exhaust gas stream from an internal combustion engine enters the inlet fitting 26 and gas passage tube 48 from the gas conveying exhaust pipe 28.

The gases move through the gas passage tube 48 into the gas transfer chamber 72 thence in retroverted directions through the gas passage tube 38 and the gas transfer chamber 70 into the exhaust outlet tube 40 which conveys the gases away from the muflier. High frequency sound Waves are attenuated in the

sound attenuating chambers

62, 64 and 66 through the acoustic couplings provided by the openings 50.

The invention includes a novel method of forming the gas passage and sound attenuating unit 44 comprising the intermediate shell 46 and the gas passage tube 48. In the method of the invention, the partitions or

baliies

52, 54, 56 and 58 are integrally fashioned on the intermediate shell 46 or in the alternative as hereinafter described, on the gas passage tube. The method involves the processing or distortion of regions of the metal of the intermediate shell or tube 46 to form the integral transversely extending partitions.

Referring to FIGURE 3, there is illustrated a step in the method of processing the metal of the wall of the intermediate shell or tube 46 in forming the baffles or partitions. The tube is mounted upon a rotatable support (not shown). The tube is rotated and the wall of the tube engaged by a suitable forming or grooving roll or wheel 74 journaled on a pin 75 carried by a member 76. In order to form a groove in the tube wall, the grooving or forming roll 74 is progressively advanced toward the tube in a direction normal to the axis 'of the tube 46 to form a groove or circular depression bounded by

portions

78 and 79.

In order to stabilize the thrust of the forming roll 74 against the tube, an abutment roller 82 journally supported on a member 84 is engaged with the peripheral surface of the tube 46 at a region preferably diametrically opposite to grooving roll 74 in the manner shown in FIGURE 3. FIGURE 3 illustrates four grooves formed in the tube 46, the forming roll 74 being illustrated in the position of completing the fourth groove. In the method of forming the grooves as above described, each of the grooves is formed individually and in succession. When the metal is distorted in forming a groove, the over-all length of the tube 46 is reduced to provide the metal for the grooves. Through this method of progressively and successively forming each groove, the thickness of the metal in the grooves is maintained substantially the same as the thickness of the portions of the tube wall 46 between the pairs of grooves so that there is no appreciable reduction in the -strength of the metal at the regions of the grooves.

The grooves are designated 51, 53, 55 and 57 in FIG- URE 3. In processing the intermediate shell member 46, the groove 51 is of the greatest depth. The

grooves

53, 55 and 57 are of progressively lesser depth although the difference between the depth of adjacent grooves may be only a few thousandths of an inch. The reason for this differential in depth of grooving will be hereinafter explained. Further steps in the method of forming the sound attenuating unit 44 are illustrated in FIGURES 4 and 5.

After the formation of the grooves in the manner illustrated in FIGURE 3, the perforated gas passage tube 48 is inserted or telescoped within the grooved walled intermediate shell 46 and the assemblymounted in vertical position upon a supporting footing or block 86, as shown in FIGURE 4. The block v86 is provided with an annular upwardly projecting ridge 88 which extends between the end regions of the tube 46 and the gas passage tube 48. The block 86 is provided with a horizontal ledge 90 which is engaged by the -lower edge of the intermediate shell or tube 46.

The block 86 is provided with a bore to slidably, yet snugly, accommodate the end region 91 of the gas passage tube 48, the end of the tube engaging or abutting the bottom wall 92 of the bore formed in the block 86. Arranged above the upper end of the assembly is a movable head 94 of a press or other means for exerting downwardly acting pressure. Secured to the press head 94 is an adapter or fitting 96 fashioned with a counterbore 97 accommodating the upper end region of the intermediate shell or tube 46.

The counterbore 97 terminates in a circular ledge 98 which is adapted to engage the upper end of the tube 46 as shown in FIGURE 4. The adapter 96 is provided with a central bore 100 to accommodate the upper end region of the gas passage tube 48. It should be noted that the wall defining the central bore or chamber 100 is slightly tapered or converged in a direction as shown in FIGURE 4 to effect a centering of the gas passage tube 48 during further processing of the shell 46 in forming the laterally extending partitions.

Surrounding the intermediate shell or tube 46 at the region of each groove is a pair of semi-circularly-shaped members 102 which engage the exterior wall of the tube 46 and provide an anuularly shaped means to confine the metal of the tube wall 46 at the regions of the grooves during further processing. FIGURE 5 illustrates the position of the assembly shown in FIGURE 4 at the cornpletion of a downward stroke of the press head or platen 94 which operation completes the formation of the

partitions

52, 54, 56 and 58.

With the components in the relation shown in FIG- URE 4 and the confining guide grips or members 102 in engagement with the exterior surface of the tube 46, downward movement of the press head 94 performs several steps in sequence. As the groove 51 at the lower end of the assembly shown in FIGURES 4 and 5, is the deepest of the four grooves, the downward pressure exerted by the press head 94 through the adapter or fitting 96 upon the upper end -of the tube 46 collapses the

portions

78 and 79 defining the groove 51 to the position shown in FIGURE 5 forming the partition 52 comprising two contiguous thicknesses of the metal which previously defined the groove 51.

At the same time the collapsing of the metal occurs, the bight portion of the groove which, as shown in FIG- URE 4, was slightly spaced from the exterior wall surface of the tube 48, is forced into engaging relation with the gas passage tube 48 under the pressure collapsing the walls defining the grooves 51.

At the completion ofthe collapsing of the walls defining the lower groove 51, solid resistance to further collapsing of the tube wall is obviated by confining dies or members 102 so that further downward pressure of the press head 94 collapses the

walls

78 and 79 defining the groove 53, such collapsing forming the dual layered partition 54.

The same collapsing action successively takes place with respect to the metal defining the

grooves

55 and 57 to form the

integral partitions

56 and 58. The progressive formation of the partitions by sequential collapsing of the walls of the grooves beginning at the bottom of the assembly occurs by reason of the diderence in depth of the successive grooves.

The progressive collapsing is assured because the resistance to collapsing of the metal regions defining the groove is dependent in a measure upon the depth of the groove. The confining members 102 surrounding the regions ofthe grooves prevent the metal of the tube or shell 46 from movlng outwardly during the collapsing step so that the lmetal defining the. grooves is..necessarily directed inwardly to effect a tight engagement of the metal forming the partitions with the exterior surface of the gas passage tube 48. A partial section of the finished product or unit 46 is shown in FIGURE 6.

It should be noted that by reason of the successive collapsing of the

portions

78 and 79 of each .groove in the tube wall 46, the length lof the tube 46 in the finished unit is the lesser length than the uncollapsed tube shown in FIGURE 4.

Due to the progressive downward .movement of the metal or tube 46 in collapsing the successive portions to form the partitions, the downward movement of the distorted metal of the tube 46 may provide a partition which is in a slightly canted position as shown in FIGURE 6, but the interior circular surfaces of the .partitions are in engagement with the gas passage tube 48 `and thereby form the

chambers

62, 64 and 66.

As will be seen from FIGURE 6, a sound attenuating and gas passage unit is provided wherein the high frequency sound attenuating chambers are fashioned or defined by inwardly extending circular partitions which are integral with the tube 46, thus eliminating the use of several independent annular members between the intermediate shell and the gas passage tube to form sound attenuating chambers. The method is particularly advantageous in that it enables the accurate location or positioning of the partitions lengthwise of the intermediate shell or tube 46.

Furthermore there is no possibility of looseness or lost motion between the partitions and the gas passage tube 48 because the collapsing step forces the inner circular edge regions defining the partitions into snug engagement with the gas passage tube 48 as shown in FIGURES 5 and 6. From the foregoing explanation of the method of forming the unit 44, the

partitions

52, 54, 56 and 58 define the annularly-shaped confined zones or high frequency sound

wave attenuating chambers

62, 64 and 66.

The completed sound attenuating unit comprising the intermediate shell 46, the perforated gas passage tube 48 and the partition construction is thus completed and is assembled in the mufiier construction as shown in FIG- URE l. As the partitions defining the high frequency sound wave attenuating chambers are formed as integral components of the intermediate shell construction 46, the complete unit is formed of only two components Viz. the intermediate shell 46 and the perforated gas passage tube 48.

The foregoing described method steps are employed in fashioning intermediate shell units where the inside diameter of the outer shell 46 is approximately 3A of an inch greater in diameter than the inside diameter of the gas passage tube 48. FIGURES 6 `and 7 are illustrative of a completed unit wherein the intermediate shell or tube 46 is of a diameter of about 21/2 inches .and the gas passage tube 48 of a diameter of about 1% inches.

The method may be utilized to form partitions between an intermediate shell and a gas passage tube by employing `an additional method step where the difference between the diameter of the intermediate shell and that of the gas passage tube exceeds approximately 3A of an inch. FIG-

URES

8 and 9 are illustrative of an additional step in fabric-ating an intermediate shell unit with a gas passage tube of reduced diameter of approximately 11/2 inches. In fashioning this form of construction, the steps of the method illustrated in FIGURE 3 are substantially duplicated in forming the grooves 108 i-n the intermediate shell or tube 110, a portion of the tube being shown in FIG- URE 8.

In order to exercise control of the metal of the shell at the regions of the grooves in forming the partitions, the metal at the region of the grooves is distorted inwardly for a greater distance than the depth of the grooves formed 7 by the method step illustrated in FIGURE 3 `and hereinbefore described. After the grooves 108 are formed in the wall of tube 110in Vthe`rnanneshown'inlIGURE Y3, the bight portion of each groove is deepened by a suitable tool 112 shovm in FIGURE 8.

The tool 112 comprises a body 114 provided with the projection 116 which is comparatively thin, as illustrated in FIGURE 8, and having a rounded end 118 engageable with the metal in the base or bight of a groove. The tube 110 is rotated `about its longitudinal axis and the tool 112 progressively moved into a groove in a direction normal to the axis of the tube to force the projection 116 toward the axis of the tube to thereby deepen the groove to approximately the configuration illustrated in FIGURE 9.

The action of forcing the tool projection 116 toward the axis of the tube while the tube is rotating effects a further distortion of the metal whereby the walls 120 and 122 defining the groove are brought more nearly into close parallel relation and simultaneously increasing the depth of Vthe groove in the tube. In assembling a gas passage tube with the construction shown in FIGURE 9, the

method illustrated in FIGURES 4 and 5 is employed to,

collapse the tube lengthwise to form the partitions.

Thus, after the tool 116 has been employed to deepen the grooves in the shell or tube 110, the gas passage tube 124, shown in FIGURES l yand ll, is inserted in the intermediate shell, and the walls 120 and 122 of each groove are brought together by the collapsing action by downward movement of the press head 94, shown in FIGURE 5, whereby the parallel walls 120 and 122 of each groove are brought into contiguous relation to form the partitions 130, as shown in FIGURE 10.

During the endwise collapsing of the intermediate shell 110, the regions of metal adjacent each of the grooves may be confined by mating semicircular confining dies 126 so that during collapsing, the metal at the region of the grooves is forced inwardly toward the gas passage tube 124. In order to effect progressive closing or collapsing of the grooves in the final step of fabricating the partitions, it is preferable that the tool 116 be moved inwardly a greater distance in each successive groove so that the grooves fro-m one end of the tube to the other are progressively deeper.

Through this method, the wall regions defining the several ygrooves are progressively collapsed by pressure on the end of the intermediate shell or outer tube in the manner illustrated in FIGURE and hereinbefore described. Through this method, the distortion of the rnetal in forming the grooves and in deepening the grooves may be controlled so as to assure the formation of partitions shaped to engage the gas passage tube 124 throughout its periphery.

Through the use of these method steps, the partitions 130 may be fashioned to bridge a substantial annular space between the gas passage tube 124 and the intermediate shell or outer tube 110.

FIGURE 12 is illustrative of a modified method of forming the partitions integrally with the intermediate shell. In this form the grooves formed integrally by distorting the metal inwardly are first collapsed to bring the

metal portions

136 and 138 of a groove into contiguous relation by endwise pressure exerted upon the intermediate shell 140 while the exterior regions of the tube adjacent the grooves are unconfined.

This action results in slight outward distortion of the metal at the regions indicated by the peripheral ridges 142 with the inner circular apices of the partitions 144 adjacent, but not yin -actual engagement, with the periphery of the gas passage tube 146. After the endwise coliapsing of the tube or intermediate shell 140 is effected, mating cavity dies 150 of semicircular shape are moved transversely into engagement with the ridges 142 to distort the metal of the ridges inwardly, which action concomitantly moves the

contiguous walls

136 and 138 of each groove inwardly with the annular bight portion in 3 engagement with the exterior peripheral surface of the gas passage tube 146.

In this manner the integral partition is brought into engagement with the gas passage tube and the exterior surface ridges of the intermediate shell are moved inwardly to present a smooth exterior cylindrical shape for the intermediate shell or outer tube 140.

FIGURE 13 is illustrative of an intermediate shell, gas passage and sound attenuating unit wherein the transversely extending partitions 162 are integrally formed with the perforated gas passage tube 164. In this construction the grooves are formed from metal from the gas passage tube 164 by forcing the metal of the tube outwardly through the use of a grooving roll such as that illustrated at 74 in FIGURE 3, the roll being carried by a member (not shown) projecting endwise interiorly of the gas passage tube and movable transversely of the axis of the tube to force the metal outwardlyV to form the grooves.

The grooves in the tube 164 are preferably made of progressively increasing depth from one end of Vthe tube to the other in the same manner that the grooves formed by the method shown in FIGURE 3 are made progressively deeper. The outer tube or shell 160 may then be assembled with the grooved gas passage tube 164- in the same manner that the gas passage tube 48 is Iassembled with the intermediate shell 46 as shown in FIGURE 4.

The gas passage tube 164 may then be collapsed lengthwise in the same general manner as illustrated in FIGURE 5, the endwise pressure exerted on the gas passage tube 164 collapsing the walls defining the out# wardly extending grooves in the tube 164 into contiguous relation and forcing them outwardly into engagement with the intermediate shell or outer tube 160 as shown in FIGURE 13. During the collapsing action on the gas passage tube 164, a mandrel or other confining means may be inserted within the gas passage tube in order to assure the outward distortion of the metal at the regions of the grooves into engagement with the intermediate shell or outer tube 160.

The adjacent partitions 162, shown in FIGURE 13, form high frequency sound attenuating chambers 166. It is preferable that the regions of the gas passage tube 164 at which the partitions 162 are formed be unperforated to provide partitions which are imperforate.

It will therefore be apparent that a sound attenuating unit particularly configurated to provide high frequency sound Wave attenuating chambers may be fashioned by forming transversely extending annularlyshaped integral partitions, either from the metal of the -intermediate shell or outer tube or from the metal of the inner or gas'passage tube. The openings 50 in the gas passage tubes provide acoustic couplings with the adjacent sound attenuating chambers formed by the outer shell and the partitions to attenuate or eradicate high frequency sound waves in a stream of exhaust gases moving through the gas passage tube.

The sound attenuating unit of the invention is thus adaptable for pre-fabrication to facilitate rapid V:assembly of one or more units in a muffler construction. The partitions fashioned in accordance with the hereinabove described method may be spaced lengthwise at different distances so as to provide sound attenuating chambers of different lengths as the grooves may be fashioned of the tube walls at any positions along a tube. The construction provides separators or partitions without the use of securing or welding individual components, rings or partitions between an intermediate shell and the gas passage tube.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

I claim:

1. The method of forming la telescoped tube assembly of two cylindrical metal tubes of diierent diameters in concentric relation including the steps of distorting metal of the wall of a first tube to form longitudinally spaced circular grooves therein, arranging said first tube in telescopic concentric relation with a second tube, and impressing pressure lengthwise on said first tube to force the metal defining the grooves to span the annular space between the tubes and into the contiguous abutting relation and engaging the second tube.

2. The method Vof forming a -telescoped tube assembly of two cylindrical metal tubes of diiferent diameters in concentric relation including the steps of distorting metal of the wall of a lirst tube to form longitudinally spaced circular grooves therein, arranging said first tube in telescopic concentric relation with a second tube, and impressing pressure lengthwise on said first tube to force the metal defining the grooves laterally to span the `annular space between the tubes and into contiguous abutting relation and engage the circular ridges provided by the grooves with the second tube.

3. The method of forming a combined gas passage means and sound attenuating unit including the steps of impressing lengthwise-spaced circumferential groves in the wall of a first tubular metal member, arranging the rst tubular member in telescoping concentric relation with a second tubular metal member of substantially different diameter, and exerting pressure lengthwise on the irst tubular member to collapse the wall regions deining the grooves into contiguous abutting relation and to span the annular space between the tubular members and thereby establish partitions and to engage the partitions with the second tubular member forming sound attenuating chambers between the tubular members.

4. The method of forming a telescoped tube assembly including the steps of distorting longitudinally spaced regions of metal of the wall of a rst tube to form transversely extending circular grooves therein whereby the grooves are of successively different depths, arranged said iirst tube in telescoping relation with a second tube of different diameter with the axes of the tubes in substan tially coincident relation, and exerting pressure endwise on said irst tube to successively further distort the metal defining the grooves into contiguous abutting relation and to span the annular space between the tubes and engage the circular ridges formed by the grooves with the second tube.

5. The method of forming a telescoped tube unit including the steps of rolling lengthwise spaced circumferential regions of a lirst metal tube to form grooves therein, arranging the rst tube in telescoping relation with a second metal tube of lesser diameter wherein the inner- 6. The method of forming a telescoped 4tube assembly including the steps of distorting metal of the wall of a irst tube to form transversely extending, longitudinally spaced circular grooves therein, deepening the grooves .to bring the wall regi-ons dening the grooves into closer relation with successive grooves of increasing depth, arranging said irst tube in telescopic relation with a second tube, and exerting pressure lengthwise of the iirst tube to further distort the metal into contiguous abutting relation and to span the annular space between the tubes with the ridges provided by the grooves in engagement with the second tube.

7. The method of forming a combined gas passage tube and sound attenuating unit including the steps of impressing lengthwise-spaced circumferential grooves of dilerent depths in the wall of a rst tubular metal member, arranging a second tubular metal member of lesser diameter within and concentric with the first tubular member, and exerting pressure lengthwise on the first tubular member while confining the exterior surfaces of the rst tubular member at the regions of the grooves to successively move the wall regions deiining the grooves into contiguous abutting relation and to span the annular space between the tubes to thereby establish partitions and engage the partitions with the second tubular member forming sound attenuating chambers between the tubular members.

References Cited by the Examiner UNITED STATES PATENTS 567,328 9/1896 Varman et al 153-73 743,193 11/1903 Rainforth 153-73 1,057,098 3/1913 Smith 138-148 XR 1,602,550 10/ 1926 Pierce 153-73 1,878,424 9/ 1932 Oldberg 181-48 2,047,442 7/ 1936 Starkweather et al. 181-48 2,147,015 2/1939 Deremer 181-53 2,157,252 5/1939 Visser et al 153-73 2,264,524 12/ 1941 Hale. 2,401,606 6/ 1946 Brown 29-455 2,485,969 10/ 1949 Johnson 153-73 2,680,901 6/ 1954 Kaiser 29-455 2,683,928 7/ 1954 Carson 29-523 2,950,777 8/ 1960 Dermer 181-48 XR 2,958,389 11/1960 Dermer 181-54 3,092,896 6/ 1963 Stinehelfer 29-454 XR 3,104,735 9/1963 Ludlow et al. 181-48 3,204,164 8/ 1965 Burke et al.

FOREIGN PATENTS 1,090,473 10/ 1960 Germany.

422,004 1/ 1935 Great Britain.

CHARLIE T. MOON, Primary Examiner. Liao sM1Low,wH1TMoRE A. wILTz, Examiners.

R. S. WARD, Assistant Examiner.

Claims

1. THE METHOD OF FORMING A TELESCOPED TUBE ASSEMBLY OF TWO CYLINDRICAL METAL TUBES OF DIFFERENT DIAMETERS IN CONCENTRIC RELATION INCLUDING THE STEPS OF DISTORTING METAL OF THE WALL OF A FIRST TUBE TO FORM LONGITUDINALLY SPACED CIRCULAR GROOVES THEREIN, ARRANGING SAID FIRST TUBE IN TELESCOPIC CONCENTRIC RELATION WITH A SECOND TUBE, AND IMPRESSING PRESSURE LENGTHWISE ON SAID FIRST TUBE TO FORCE THE METAL DIFINING THE GROOVES TO SPAN THE ANNULAR SPACE BETWEEN THE TUBES AND INTO THE CONTIGUOUS ABUTTING RELATION AND ENGAGING THE SECOND TUBE.