US2220866A

US2220866A - Exhaust silencer

Info

Publication number: US2220866A
Application number: US249694A
Authority: US
Inventors: Jensen Gunnar; Walter H Powers
Original assignee: Walker Manufacturing Company of Wisconsin
Current assignee: Walker Manufacturing Company of Wisconsin
Priority date: 1939-01-07
Filing date: 1939-01-07
Publication date: 1940-11-05
Anticipated expiration: 1957-11-05

Description

Nov. 5, 1940. G. JENSEN ETAL EXHAUST SILENCER 2 Sheets-Sheet 1 Filed Jan. '7, 1939 ATTORNEYS.

IN VENTOR Nov. 5, 1940: G. JENSEN ETAL EXHAUST SILENCER Filed Jan. '7, l939 2 Sheets-Sheet 2 [N VENTORQ ar' Jenaerz er 7'7. Powers:

Yfi A T T ORNE Y Patented Nov. 5, 1940 UNITED STATES PATENT OFFICE Mich., assignors to Walker Manufacturing Company of Wisconsin, a corporation of Wisconsin Application January 7., 1939, Serial No. 249,694

16 Claims.

This invention relates to muiller constructions.

More particularly, it relates to a novel and improved exhaust silencer construction primarily intended for attenuating the sound emanating from the exhaust of internal combustion engines of the type commonly used in the present day automotive vehicles.

The present invention relates primarily to the so-called straight-through type of mufilers and contemplates the provision of particularly simple, cheap, and quiet mufiier constructions, which are eiiective in attenuating the sounds set up by the internal combustion engine, and particularly the objectionable harmonics of the firing frequency. It is generally considered that the most objectionable harmonics o1"- the firing frequency are the second harmonic at the lower speeds and the first harmonic at the higher speeds, andthe present construction is particularly designed to attenuate such harmonics without high backpressure.

While the mufiler herein disclosed is primarily directed to a construction which is particularly effective in a general attenuation of the above 25 harmonics, it will be readily appreciated that muffler constructions formed in accordance with the teachings of the present invention have certain inherent advantages in eliminating other objectionable sounds normally occurring in the exhaust system.

Many other and further obvious advantages and features of the invention will become readily apparent upon consideration of the following specification in connection with the accompany- 35 ing drawings forming a. part thereof.

In the drawings:

Figure l is a longitudinal sectional view illus trating in detail a muiiler construction embodying the principal features of one form of the in- 40 vention;

Fig. 2 is a longitudinal sectional view similar to Fig. 1, illustrating a muffler construction embodying a modified form of the invention;

Fig. 3 is a transverse sectional View, taken on 45 the line 33 of Fig. 1 and illustrating in detail the construction and arrangement of the attenuating member; a

Fig. 4 is a longitudinal sectional view, illustrating a furthermodification of the invention; 50 Fig. 5 is a transverse sectional view taken along the line 5-5 of Fig. 4; and

Fig. 6 is a fragmentary longitudinal sectional view illustrating a further modification of the invention.

With more particular reference to the drawings and specifically to the embodiment of the invention shown in Figs. 1 and 3 thereof, it will be seen that the muffler construction comprises a generally cylindrical casing or outer shell 5, which is provided with conventional front and rear end 5 wall members 6 and 1., respectively, which may be welded or otherwise secured to the outer shell in any suitable conventional manner. The end wall member 6 is provided with an axially extending, centrally disposed neck 8, which serves 10 to provide means for connecting the forward end of the muilier to a pipe (not shown), which as is conventional in constructions of this character, serves to interconnect the muiller with the exhaust manifold of the engine with which the 16 mufiler is used. Similarly, the end wall l is provided with an axially extending, centrally disposed neck 9, which serves to provide means for connecting the conventional tail-pipe (not shown) to the mufiler construction. 20

Adjacent the forward end of the mufiier isv mounted sound attenuating member ID, which at its outer periphery is provided with an axially extending flange it and which, in the present instance, extends to and is snugly but slidably seated within the shell *5. In the illustrated form, the member it] is generally cone-shaped, although, in the broader aspects of the invention, other forms may be used. Adjacent its central portion, the member is provided with a projecting neck i2 and is also provided with a radially, inwardly directed annular flange l3, which serves to define a restricted orifice it of smaller cross-sectional area than the inlet opening provided by the neck 8. The neck i2 is received within and is welded 5 to the forward end of a primary exhaust passage or tube 175, whereby the member ID serves as a support for the tube H5. The tube l5 extends from the member I 0 to the rear end of the muffler and is welded in telescoped relation within the 40 neck 9 at the point it.

The conical portion of the member ID is provided with'a plurality of relatively small openings 20, the purpose and function of which will hereinafter be described in greater detail. Intermediate the front and rear ends of the mufller and spaced at a distance substantially rearwardly of the midpoint is a partition member 2i, which serves, together with the member ID, to

define an annular chamber 22 surrounding the forward end of the primary exhaust tube l5. Adjacent the rear end of the muflier is a similar partition member 23, which, together with the partition member 2| and outer shell 5, serves to define a resonator chamber 24. The partition member 23, together with the rear end wall member 1, and outer shell 5, serves to define a spit chamber 25 at the rear end of the mullier construction as a whole. The partitions 2| and 23 5 are each welded to the tube l5 and are snugly but slidably seated within the shell 5.

The portion of the primary exhaust tube lying within the chamber 22 is provided with a plurality of relatively closely spaced tangentially discharging louvers 21, which may be conveniently constructed in accordance with the teachings of. the Gunn Patent No. 1,949,074, assigned to the assignee of the present invention.

An annular series of louvers 28 are formed in the primary exhaust passage adjacent the rear end of the sound resonating chamber 24. This sound resonating chamber 24 preferably has a tuning neck 30 secured in position on the partition member 23 and extending forwardly therefrom, to a point adjacent to, but spaced from, the partition member 2|. From this construction, it will be obvious that sound waves and exhaust gases passing through the primary exhaust passage |5 may be discharged in a tangential direction within the tuning neck 30 and through this tuning neck may pass into and out of the resonating chamber 24.

A series of louvers 32 may similarly be provided on the primary exhaust conduit throughout that portion thereof which is disposed within the spit chamber 25 and it will, of course, be understood that this spit chamber functions in the conventional, well recognized manner, merely serving the purpose of eliminating certain of the unpitched sounds normally emanating from a muffler system.

The resonating chamber 24 may be constructed and proportioned for the elimination of the tailpipe resonances and may be regulated for the primary purpose of eliminating come-down noises, or may be constructed and arranged for any suitable purpose in order that its operation will obtain the maximum eil'ectiveness.

As explained above, the chamber 22 and associated parts areprimarily intended for the purpose of eliminating the harmonics of the firing frequency. The restricted opening |4 causes a portion of the gases and sound waves entering the muffler to be bypassed through the perforations 20in the cone Ill. The aggregate area of the openings l4 and 20 maybe proportioned in such a manner that an undesirable degree of backpressure will not be created in the muffler system as a whole. Sound waves and exhaust gases will pass inwardly and outwardly through the louvers 21, into and out of the chamber 22 as a result of pressure fluctuations inherent in muilier systems of this general type and due to tangential discharge from the louvers will set up a swirl in the chamber 22, as described in the Gunn patent referred to above. The sound waves and exhaust gases which are bypassed through the openings 20 in the member llwill re-enter the primary exhaust passage through the louvers 21 and the destructive interference causes by the gases passing into and out of the louvers as well as through the openings "has been found to effect a very marked attenuation of sound, which has been found to be particularly effective in eliminating 70 the harmonics of the firing frequency.

It will be further understood from the foregoing description of the .present embodiment of the invention, that in a generic sense, the primary exhaust passage, such as It, should be 75 arranged so that suiiicient back-pressure exists therein to cause a desired quantity of the exhaust gases to be bypassed through the openings 20in the sound attenuating member III, In the present instance, this back-pressure is produced in part by the restrictor i4, and 5 in part by the inherent resistance to flow through the passage l5, and it will be understood that the size of the restrictor I4 is determined in accordance with the degree at which the inherent backpressure is required to be supplemented in order 1 to produce the desired degree of total back-pressure in the primary passage. In a generic sense, and in certain instances-such as where the primary exhaust passage is relatively long and of relatively small diameter, the inherent back- 15 pressure created thereby may be substantial enough to enable the restrictor H to be provided with a substantially larger opening than that shown, or to be dispensed with entirely. Again, in other instances, as where the primary 20 exhaust passage has only a very low back-pressure, it may be necessary to increase the eiIect of the restrictor l4, by correspondingly decreasing the size of the opening therein.

Outside of the effective. sound attenuating 25 characteristics of the system, it will be readily appreciated that the above described construction is exceedingly cheap and simple to manufacture. The perforated member not only serves the purpose of providing a support for the forward end of the primary exhaust passage i5, but may be preformed in such a way that this member also serves to provide the restricted orifice H as a unitary integral part of the member iii. further be readily appreciated that the muilier as a whole is simple in construction, and easily fabricated.

In the modified form of the invention shown in Fig. 2, the construction shown comprises an outer shell 35 having front and rear end wall members 36 and 31, respectively, similar in construction to the end wall members 6 and 1, described in connection with the preferred embodiment of the invention. In the modified form of the invention, the primary exhaust passage is discontinuous and includes a forward section 38 which may be mounted in direct communication with the inlet opening and which may have its front end supported by a suitable neck 39 which telescopes over the forward end of the section 38 and tele- 5o scopes into the inlet opening. The rearend of the section 38 of the primary exhaust passage is supported by means of a partition member 4| which may be annularly corrugated and have its outer flange 42 welded directly to the outer shell 5 35 and an inner annular flange 43 welded in telescoping relation to the rear end of the section 38 of the primary exhaust conduit. It will be readily and function of the annular corrugations movement between the section 38 and the outer shell, thereby greatly facilitating relative movement of these parts as a result of expansion and contraction due to heating and cooling. A perforated member 45 similar in construction and arrangement to the perforated member II is mounted directly rearwardly of the partition member 4| and includes an outer flange 46 which may be slidably seated within the outer shell and at its central portion may include an axially ex- 7 tending cylindrical portion 41, provide a telescoped mounting for the forward end of a second section 42 of the primary exhaust passage, the rear end of which is telescoped into the discharge o ening in the end waiimember which serves to 31; The central portion of the perforated member 45 is preformed to provide a restricted orifice 50 which, as described in connection with the preferred embodiment of the invention, serves to cause the bypassing of a portion of the gases and sound waves through perforations II in the conical portion of the member I.

The chamber between the front end wall member 36 and partition member ll serves to provide a primary expansion chamber {I and the gases and sound waves which are discharged from the rear end of the front section of the primary exhaust conduit 38 in part will pass through the orifice 50 and in part will be bypassed .through l the perforations 5| in the member. It will be readily appreciated that the sound attenuating chamber 56 formed by the outer shell, rear end wall 31, and perforated member 45 will function in substantially the same manner as the chami?" ber 20, described in connection with the preferred embodiment of the invention.

The arrangement of Figs. 4 and 5 illustrates the adaptation of a sound attenuating member analogous-to. the previously described members l0 and to muiiler constructions utilizing an inner shell interposed between the outer shell and the primary exhauht passage.

The muflier construction shown comprises a generally cylindrical outer casing 69 which has its ends closed by means of partition members 86 and $1 at the front and rear thereof, respectively.

As in the previous embodiments, these, partition members are respectively provided with necks B8 and 69 and it will, of course, be understood that F the neck 58 is adapted to be secured in communication withthe rear end of a pipe (not shown) connecting with the exhaust manifold oi an internal combustion engine of an automotive vehicle. The neck 69 is intended for direct con- U nection with a tail pipe (not shown) as is customary in constructions of this general character.

The outer shell 65 is provided, intermediate its ends, with a member'lil, the outer flange whereof 45 is secured, as by welding, to the shell 55, and the inner flange H whereof is similarly secured to an axially extending primary exhaust tube or pipe l2. This tube or pipe 12 extends substantially throughout the entire axial length of the mother construction and has its rear end l3 slidably but snugly supported within theneck 69 at the rear end of the muiiler. The forward end of the tube or pipe 12 is supported in the manner herein= after described in detail.

An inner shell 15 of cylindrical configuration and having a diameter substantially smaller than the outer shell but considerably larger than the tube 12 is axially arranged withlnthe shell 85 and has its forward end flanged at 18 and secured,

as by welding, to the end wall 68. Its rear end is similarly flanged at I1 and is correspondingly secured to the partition member 10. Within the inner shell 15 is a sound attenuating member 80 which serves to support the forward end oi the tube 12 and which has a radially extending portion 8| provided 'with an-axially extending flange 82 snugly but slidably seated within the inner shell 15. The member 8! is provided with a restricted axial opening 85 of materially smaller diameter than the diameter of the tube 12 which serves to restrict the flow of gases through the primaryexhaust tube 12. The radially extending portion of the member is provided with a clrcumferentially arranged series of openings 81 N which serve to permit a portion of the gases entering the forward end of the mufller to pass into the space between the inner shell II and the primary exhaust tube 12.

A partition member 80 of conventional form is secured to the primary exhaust tube 12 and is I snugly but slidably seated within the inner shell- 15 intermediate the ends of the intermediate shell 15. The portion of the primary exhaust tube between the partition'member Ill and the partition member is provided with a'series of tangential- 10 1y disposed louvers 92 of any suitable form, these louvers preferably being constructed in accordance with the disclosure of Gunn Patent No.

1,949,074, assigned to the assignee of the present invention. The' chamber formed by the interl5 mediate shell 15 and the partition members 10 and 90 constitutes a small spit chamber such as is conventionally employed for the elimination of unpitched sounds in the high frequency range.

The primary exhaust conduit 12, throughout W the portion thereof which is disposed between the member 80 and the partition member 99, is provided with a plurality of tangentially disposed discharge louvers lllll similar to the louvers de-= scribed above, and which afford communication between the interior of the tube 112 and the interior oi the inner shell lit. In turn, the inner shell .75 is provided with an annular series of openings 95 which serve to provide communication between the interior oi the intermediate shell and the chamber formed by the outer casing t6 and the end wall Bil, the partition ill, and the intermediate shell ii). The openings 95 are il lustrated as being positioned adjacent the ion ward end oi the shell lb, but depending upon operating considerations, may be positioned near the rear end of the shell lii, intermediate the ends thereof, or may be distributed therealong.

The sound waves and exhaust gases entering the interior of the intermediate shell lit through the openings ill and the louvers we may enter the closed resonator chamber formed between the outer shell wand the intermediate shell it; and it will be readily appreciated that the forward portion of the intermediate shell it acts as tuning means through which this communication is e tablished. g

The rear portion of the muiller rearwarclly of the partition member i0 is divided into two nuiar chambers by means of a member Hi5 which is in the nature of a partition member extending between the outer shell $5 and the primary exhaust conduit ll. andis provided with an annular series of openings ldli which permit axial communication between the chamber new defined by the partition members l0 and IE5 and the outer shell and the primary exhaust conduit l2 and the member lOB defined by the partition M5 and end wall member 81. The portion of the primary exhaust tube 12 lying within the'cham- 3 her H08 is provided with a plurality of tangentially discharging louvers 9 similar in construction to the louvers 92 and Hill described above and it will be seen that exhaust gases may pass outwardly through these louvers through the openso ings I06 into the chamber I01. It is noted that the portion of the primary exhaust tube 12 lying within the chamber Hill is lmperforate and it will be readily appreciated, therefore, that the chamber lfl'l is entirely closed except for the openings I06.

This construction-at the rear end of the muffler is particularly effective in its silencing action because of the fact that the sound waves mus pass through the restricted louvers III in the pri- 7 mary exhaust tube before reaching the tuning apertures III in the partition member III! which apertures in addition offer resistance which is very important in that the controlling of this resistancebroadens the frequency response of the chambers to such an extent that it covers quite a large frequency range.

The arrangement shown in Fig. 6 corresponds to the arrangement shown in Figs. 4 and 5, except in respect to the form and supporting relation of the sound attenuating member.

In Fig. 6, the filter member a pair of neck portions H2 and Ill, which are connected together by a radially extending portion H8, and the latter whereof terminates ina radially extending flange H6 which is secured, as by welding, to the end partition 56. The neck portion H2 is snugly but slidably received within the forward end of the primary exhaust tube 12 and so constitutes a support for such forward i end in the manner described above with reference to Figs. 4 and 5. The neck portion H4 is correspondingly snugly but slidably seated within the forward end of the inner shell 15, and so affords a support for the forward end of the inner shell. As in the previous embodiment, a flow restricting opening 85 is formed in the base of. the member I III and the radially extending portion H8 is provided with a series of openings 81, the function and arrangement of these openings being as described above.

It will be appreciated from the foregoing that l many very substantial modifications of the above specifically described muffler constructions may be made, which at the same time will fall within the scope of the invention, as set forth in the claims.

What is claimed is:

1. In a straight-through muffler construction having an outer shell, an apertured conduit providing a portion of the primary exhaust passage through said shell, an apertured baffle means p0- sitioned between the shell and conduit and serving to support the forwardend of the conduit in predetermined position within said shell, said baffe extending interiorlyof said conduit and serving to restrict flow therethrough.

2. In a straight-through muffler construction having an outer shell, an apertured conduit providing a primary exhaust passage through said shell, the forward end of said conduit being spaced from the forward end of said shell, and an apertured baffle member telescoped within said shell, said baille member being preformed to provide an axial projection adapted to telescope within and support the forward end of said conduit.

3. In a straight-through mufller construction having an outer shell, an apertured conduit providing a primary exhaust passage through said shell, the forward end of said conduit being spaced from the forward end of said shell, and an apertured baffle member positioned within said shell, said baffle member having an apertured part extruding into said conduit so as to restrict flow through said conduit and having an .apertured part positioned between said conduit and said shell to afford a bypass around said restriction.

l to is provided with chamber, and flow restricting means positioned in said conduit toward the forward end of said mufller from said rearward partition, said conduit being imperforate between the flow restricting means and the forward one of .said partitions, the forward one of said partitions being apertured, and said mufller having a byrpass circuit through said apertured partition into said chamber around said flow restricting means.

5. In a straight-through mufller construction having an outer shell, first and second conduits positioned within said shell in axially spaced relation to each other and forming together a straight-through but discontinuous primary exhaust passage through said'shell, partition members associated with the rearmost one of said conduits and extending between such one conduit andthe shell so as todeflne a chamber adjacent the rear end of the shell, and flow restricting means positioned in said rearmost one of' the conduits, said rearmost one of the conduits being apertured rearwardly of the flow restricting means and the forward one of the partition members being apertured to provide a by-pass into said chamber around the flow restricting means.

6. In a straight-throughfmufller construction having an outer shell with the forward end thereof spaced rearwardly from the front end of the shell, a conduit within said shell and having openings in the surface thereof serving to provide communication between the interior of said conduit and the interior of said shell, flow restricting means positioned in said conduit forwardly of said openings, and a sound attenuating member positioned within the shell and extending from the shell to the conduit, said sound attenuating member being apertured so as to establish communication between the interior of the shell and the portion of said conduit forwardly of said flow restricting means.

- '7." In a straight-through muffler construction having an outer shell, an apertured inner shell positioned within said outer shell with the forward end thereof spaced rearwardly from the front end of the shell, a conduit within said shell and having openings in the surface thereof serving to provide communication between the interior of said conduit and the interior of said shells, flow restricting means positioned in said conduit forwardly of said openings, and a sound attenuating member positioned within said outer shell and associated with said conduit so as to establish communication between the interior of said shells and the portion of said conduit forwardly of said flow restricting means.

8. In a straight-through mumer construction .having an outer shell, an apertured inner shell positioned within said outer shell with the forward end thereof spaced rearwardly from the front end of the shell, a conduit within said shell and having openings in the surface thereof serving to provide communication between the interior of said conduit and the interior of said shells, flow restricting means positioned in said conduit forwardly of said openings, and a sound attenuatingmember positioned within said outer shell and associated with said conduit so as to establish communication between the interior of said shells and the portion of said conduit forwardly of said flow restricting means, said sound attenuating member being supported by said outer shell and acting to support said inner shell and said conduit.

9. In a straight-through muiller construction having an outer shell. an apertured inner shell 16 amass positioned within said outer shell with the fcrward end thereof spaced rearwardlyv from the front end of the shell, a conduit within said shell and having openings in the surface thereof serving to provide communication between the intericr of saidconduit and the interior of said shells, ilow restricting means positioned in said conduit forwardly of said openings, and a. sound attenuating member positioned within said outer shellandassociatedwithsaidconduitsoasto establish communication between the interior of said shells and the portion of said conduit forwardly of said flow restricting means, said sound attenuating member being supported by said inner shell and being adapted to support said conduit.

10. In a straight-through muiller construction having an outer shell, an apertured conduit provlding a primary exhaust passage through said shell, the forward end of said conduit being spaced from the forward end of said shell, an apertured baille member positioned within said shell and extending radially from said conduit to said shell, and a flow diverting element positioned in said conduit adjacent the forward end of the conduit. s

11; An exhaust silencer comprising, in combinaticn, a shell part having an inlet and snoutlet, means including primary exhaust tube means positioned within said shell part in such relation that the space between the shell part and the tube constitutes a silencing chamber having a closed rear end, the tube means having a perforate part to afford communication between the interior of the tube and the chamber, the silencer having an expansion chamber between the inlet and said tube means of larger cross-sectional area than the tube means, and means affording communication between the expansion chamber and the silencing chamber in by-pass relation to the perforate part of the tube means.

12. An exhaust silencer comprising, in combination, a shell part having an inlet and an outlet, means including primary exhaust tube means positioned within said shell part in such relation that the space between the shell part' and the tube constitutes a silencing chamber having a closed rear end, thetube means having a P forate part to afford communication between the 5. interior of the tube and the chamber, the silencer having an expansion chamber between the inlet and said tube means of larger cross-sectional area than the tube means, means affording communication between the expansion chamber and g the silencing chamber in by-pass relation to the perforate part of the tube means, and flow diverting means positioned in said tube means adiacent the said expansion chamber.

13. An exhaust silencer comprising, in combinatiomashellparthavlnganinletandanoutlet, a primary exhaust e positioned within the shell part with the inlet end thereof spaced rearwardlyfromthesaldshelllnlet,the space between the tube and the shell part constituting U a silencing chamber, the tube having an apertured part to afford ccmmimication between the interior of the tube and the silencing chamber and thechamberbeingclosedatitsrearendthe silencer having between the shell inlet and the inlet end of the tube an expansion chamber of greater cross-sectional area than the tube, and

means affording communication between the expansion chamber and the silencing chamber in by-pass relation to the said apertured part of the tube.

14. An exhaust silencer comprising, in combination, a shell part having an inlet and an outlet, a primary exhaust passage positioned within the shell part with the inlet end thereof spaced rearwardly from the said shell inlet, the space between the tube and the shell part constituting a silencing chamber, the tube having an apertured part to afford communication between the interior of the tube and the silencing chamber and the chamber being closed at its rear end, the silencer having between the shell inlet and the inlet end of the tube an expansion chamber of greater cross-sectional area than the tube, means aifcrding communication between the expansion chamber and the silencing chamber in by-pass relation to the said apertured part of the tube,

and a flow diverting means positioned in the tube adjacent the inlet end thereof.

15. An exhaust silencer comprising, in combination, a shell part having an inlet and an outlet, a primary exhaust passage positioned within the shell part with the inlet end thereof spaced rearwardly from the said shell inlet, the space between the tube and the shell part constituting a silencing chamber, the tube having an apertured part to aiford communication between the interior of the tube and.the silencing chamber and the chamber being closed at its rear end, and apertured partition means between the tube and the shell part adjacent the inlet end of the hibe forming the front end of the silencing chamber and cooperating with the shell part to define an expansion chamber between the shell inlet and the inlet end of the tube of larger cross sectional area than the tube.

16. An exhaust silencer comprising, in combl-,- nation, a shell part having an inlet and an outlet, a primary exhaust passage positioned within the shell part with the inlet end thereof spaced rearwardly from the said shell inlet, the space tured part to aflord commimication between the interior of the tube and the silencing chamber and the chamber being closed at its rear end,- apertured partition means between the tube and the shell part adjacent the.lnlet end of the tube forming the front end of the silencing chamber and cooperating with the shell part to define an expansion chamber between the-shell inlet and the inlet end of the tube of larger cross-sectional area than the tube,.and a flow diverting means positionedinthetubeadlacenttheinletend thereof.

GUNNAR JENSEN.

wan'raa n. rownas. o

I CERTIFICATE OF CORRECTION. Patent No." 2,220,866- November 5, 1%.0. I

GUNNAR JENSEH ET AL. w

hereby certified that error' appears in the printed specificetioh oi the above nmnbered-patent requiring correction ae follows: Page 1 sec- -ond column, lines 27, 28 and 29,.l inee 15,1414. end. lines 58, 59 and 60,

and page 5, first column, lines 1; 2 and 3, claimei, 7, and 9'respoc tively, for the words "outer shellwith the forward. end thereof spaced rearwardly from the front end .of the shell, e condnit within said shell" rend "outer shell, a conduit within said ehellwith the forward end thereof.-

spaced rearwardly from the front end 5; the 8hOIl and that the said. Let ters Patent ehofildbe read with this correction therein that the same guy conform to the record of the case in the Patent Office.

Signed andsealed this 21st day of January, A. 1). 19t

Henry Van Aradele, (Seal) I Acting Commissioner of Patents.

spaced rearwardly from the ifront end of the ahell and that the acid Let I CERTIFICATE OF commoner. 1 I Patent NO-L 2,220,866. November 5,- i-9h 0.

GUNNAR JENSEN ET AL. hereby certified that errox appears ili printed apecifiqotloh a: the above numbered-patent requirigg correction ac follows: Page 1;, ceco d colmnn, 11:19:27, 28 and 29,.l inee 145,111; and 145, lines 58, 59 and 60,

and page 5, first column, lines 1; 2 and 3, claimi, 7, 8 anti 9'respec"- tively, for the words "outer shell with the forward end thereof epgced pearwardly from the front and .of the shell, a conduit within said shell" read "outer shell, a conduit within said shell with the forward end thereof.

tera Patent ahofild be head with this correction therein that conform to the recoi'd of the case in the Patent Office.

the acne n lq Signed and's ea'led this am day of Januar A. 1). 19in. x

I .t Henry Van Anadalle, 7 (Seal) 4 Acting Commissioner of Patents.