US2063658A

US2063658A - Fluid muffler

Info

Publication number: US2063658A
Application number: US41906A
Authority: US
Inventors: Harley H Bixler
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1935-09-24
Filing date: 1935-09-24
Publication date: 1936-12-08
Anticipated expiration: 1953-12-08

Description

H. H. BIXLER FLUID MUFFLER Filed Sept. 24, 1935 www Inventor: Harleg H. Bixler,

Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE FLUID MUFFLER New York Application September 24, 1935, Serial No. 41,906

11 Claims.

My invention relates to fluid mufllers and more particularly to muillers for refrigerating machine compressors or the like.

It is an object of my invention to provide an 5 improved muffler for a refrigerating machine compressor or the like which is compact and rugged in construction, which requires a minimum number of parts, and Which may be readily assembled and disassembled for purposes of repair and cleaning.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing, in which Fig. 1 is a side elevation, partly in section, of a refrigerating machine provided with an intake muffler embodying my invention; Fig. 2 is an enlarged perspective view, partly in section, of the intake muffler of the refrigerating machine shown in Fig. 1; Fig. 3 is a perspective view of the removable sleeve of the intake muffier shown in Figs. 1 and 2; Fig. 4 is a perspective View of a retaining plug of the intakemuffier shown in Figs.. 1 and 2; and Fig. 5 is a perspective View, partly in section, of a modified form of removable sleeve embodying my invention, which may be utilized in the intake muffler shown in Figs. 1 and 2.

Referring to the drawing, I have shown in Fig. l a refrigerating machine designed for household use which includes a compressor ID, which is rig'- idly mounted on the top of a vertical electric driving motor I I by screws I2. The driving motor II and compressor I0, which are thus secured together as a unitary structure, are mounted on 40 a series of vertical helical compression springs I3 the upper ends of which are secured to laterally extending feet I4 welded, or otherwise rigidly secured, to the sides of the frame of the motor II.

The compressor and the driving motor therefor 45 are enclosed by a cylindrical hermetically sealed casing I5 made of sheet steel or the like. Vaporized refrigerant, such as sulphur dioxide, compressed by the compressor I is supplied to an air cooled natural draft condenser I6, which surrounds the casing I5, and is liquefied therein. Liquid refrigerant is supplied from the condenser I6 through a flow controlling float valve in the float valve casing I'I to a flooded type evaporator I8 located in a compartment, such as the food storage compartment of a household type refrigerator, which is to be cooled. The casing I is mounted on a heat insulated removable top wall I9 of the compartment in which the evaporator I8 is located and the evaporator I3 is supported on the lower side of the Wall I9. The liquid refrigerant in the evaporator I8 is vaporized by the absorption of heat from the interior of the cornpartment in which the evaporator is located and refrigerant thus vaporized is returned to the interior of the casing I5. The interior of the casing I5 is thus maintained at a comparatively low pressure being approximately the same as that prevailing within the evaporator I8.

The low pressure vaporized refrigerant within the casing I5 flows to the compressor I0 through an intake muffler 20 embodying my invention. The upper end of the intake muliier 20 is supported by a U-shaped intake conduit 2l through which vaporized refrigerant is conveyed to the inlet port of the compressor. The upper ends of a U-shaped discharge conduit 22 and the U- shaped intake conduit 2I are secured to a mufe box 23 which is in turn secured to the end of the cylinder of the compressor I0 by bolts 24. A discharge muffler 25 is secured to the lower end of the discharge conduit 22. The provision of a mullle box for a refrigerant compressor having depending intake and exhaust conduits secured thereto, which in turn support intake and exhaust mulers at the lower ends thereof as a unitary structure, forms no part of my present invention, but is described and claimed in my copending application, Serial No. 26,797, filed June 15, 1935, and assigned to the General Electric Company, the assignee of my present invention.

The intake muffler 20 includes' a cylindrical outer casing 26 and a cylindrical sleeve 32 positioned within the casing and arranged to provide an extended reverse-flow fluid muflling path of substantially twice the length of the sleeve. A relatively long fluid muling path is thus provided within a compact structure. The lower end of the cylindrical sleeve 32 is closed by a plug 40 removably inserted in one end of the sleeve for retaining the sleeve in position. Such a construction facilitates the assembly and disassembly of the muffler during manufacture and for purposes of cleaning and repair.

In the form of my invention illustrated in Figs. 1 to 4, inclusive, the mufller 20 includes an outer tubular casing 26, which is preferably cylindrical in shape, the upper end thereof being closed by a metal cap 21 which extends across the same.

The cap 2 is provided with an annular indentation 28 in which the upper edge of the casing is tted and to which it is brazed, or otherwise joined. The cap 2l is also provided with an upstanding cylindrical portion 29 having an outlet opening 3G formed in the center thereof and surrounded by a peripheral flange 3l. The lower end of the intake conduit 2l is brazed, or otherwise attached, to the flange 3l. A tubular sheet metal split sleeve 32, which is preferably cylindrical in shape, is removably positioned in the casing 26. The sleeve 32 may be punched or otherwise formed from a sheet of suitable sheet metal, such as shee steel, and then bent in the form of a cylinder with the

longitudinal edges

33 and 34 thereof arranged in spaced relation. The sleeve 32 is given a diameter slightly larger than the interior diameter' of the casing 26 so that the sleeve 32 will be somewhat compressed upon its insertion within the casing 26. Consequently, the sleeve 32 resiliently engages the interior walls of the casing ZG and is thus maintained in position within the casing. Even when the sleeve 32 is compressed within the casing 26, however, the

longitudinal edges

33 and 34 thereof are maintained in spaced relation, as best shown in Fig. 2, in order to provide an outlet for liquid lubricant, as hereinafter described.

The sleeve S is provided with a series of three symmetrically arranged longitudinal grooves or indentations 35 in the cuter surface thereof which extend substantially throughout the length of the sleeve. The indentations 35 communicate at their upper ends with a series of corresponding inlet openings or ports 36 extending through the side walls of the upper portion of the casing 26. The inlet openings are preferably located adjacent the top of the casing 2S in order that they shall be well above the level of the lubricant 3l in the bottom of the casing l5. Elongated ports or openings 3G are formed in the sleeve 32 adjacent the low-er ends of the indentations 35 and provide a communication between the indentations and a chamber 39 formed within the sleeve rEhe openings 3S are preferably elongated in the direction of the longitudinal axes of the indentations 35 in order to provide large free openings through which the vaporized refrigerant passing through the indentations may enter the chamber 39. It is particularly important that an unrestricted passage should be provided for :le vaporized refrigerant at such points since it reverses its direction of flow upon entering the chamber' 39 and moves upwardly therethrough. The lower end of the sleeve 32 is closed by a removable cup-shaped sheet metal plug 40 which is tightly tted therein and is presented away from the adjacent end of the sleeve. The plug 40 and sleeve 32 are provided with registering holes 4l and 42. A suitable registering hole is formed in the casing 23 and a screw 43 passing through the registering holes is threaded in a tapped hole formed in the adjacent portion of the frame of the driving motor il, as shown in Fig. l. The lower end of the intake muilier 2D is thus rigidly secured to the motor frame. rI'he lower ends of the casing 26, sleeve 3?., and plug l0 are preferably cut off at an angle of approximately 45 in order to facilitate the insertion and removal of the screw 42 and in order to facilitate the drainage of oil therefrom.

During operation of the refrigerating machine, vaporized refrigerant enters the muilier through the inlet openings 3B and passes downwardly through the elongated fluid muiiiing passages formed by the indentations 35 and the co-operating adjacent portions of the casing 26. The vaporized refrigerant then passes through the openings 38 into the chamber 39 formed within the sleeve 32 and passes upwardly therethrough to the outlet opening 33 formed in the cap 21. A relatively long reverse-flow fluid mullling path is thus formed between the inlet and outlet. Since the vaporized refrigerant passing through the muffler passes downwardly throughout substantially the entire length of the sleeve 26 and then upwardly throughout the same distance in the chamber 39, it traverses a path of substantially twice the length of the sleeve and a relatively long path is thus provided while the length of the muffler structure is minimized. In a mufer such as I have illustrated, designed for use in conjunction with a sulphur dioxide refrigerant compressor, in which the maximum rate of fluid now into the compressor is not more than four cubic feet per minute, each of the three passages formed by the indentations 35 should have a cross eetional area of approximately .015 square inch and having a length of at least 30 to 40 times the diameter of a pipe having an equivalent cross sectional area. The relatively restricted channels formed by the indentations 35 in the sleeve 32 eifeotively damp out a major portion of the vibratory or wave-like motion of vaporized refrigerant passing to the compressor. At the beginning of the opening movement of the inlet valve of the compressor it sticks momentarily due to surface adhesion, so that the pressure within the compressor cylinder is substantially less than that prevailing in the intake conduit and intake muifler before the valve opens. As a consequence, a sudden surge oi vaporized refrigerant tends to enter the compressor and if no muffling arrangement were provided this surge of vaporized refrigerant would result in the transmission of a. vibratory wave within the audible range in the casing and cause the machine to be noisy. Upon the opening of the inlet valve, the vaporized refrigerant within the intake conduit 2| tends to rush into the compressor and the relatively large volume of refrigerant within the chamber 39 of the muffler provides a large reserve supply of refrigerant which passes into the intake conduit. The columns of vaporized refrigerant in the relatively narrow passages formed by the indentations 35 in the sleeve 32 have a sufficiently high inertia that the energy of the wave motion set up in the vaporized refrigerant within the intake conduit 2l and chamber 39 is substantially all dissipated in moving such columns of vaporized refrigerant. As a consequence, the noise caused by the wave motion of the vaporized refrigerant entering the compressor is minimized.

If any lubricating oil, or the like, is trapped in the va-porized refrigerant entering the mufiler 20, it rst collects in the bottom of the chamber 39 on the head of the plug 40 and then drains from the muflier through the passage formed between the spaced

longitudinal edges

33 and 34 of the sleeve 32. The lower corners 44 of the

longitudinal edges

33 and 34 of the sleeve 32 are preferably rounded in order that any vaporized refrigerant entering the muffler over the same will not cause a hissing noise. Since the lower end of the plug 40 slopes downwardly from the passage between the

edges

33 and 34 of the sleeve 32 any oil draining out of the muffler will run rapidly down the lower edges of the plug away from the passage. Consequently, the possibility of the oil being drawn back into the interior of the muffler is minimized.

In assembling the muffler described above on the refrigerating machine, the intake conduit 2l and exhaust conduit 22 are first brazed, or otherwise rigidly secured to the muflle box 23. The intake muffler casing 26 is then brazed to the lower end of the intake conduit 2| and the discharge mufller 25 is brazed to the lower end of the discharge conduit 22. The muiile box, intake and discharge conduits, discharge muffler and intake mufller casing are thus assembled as a unitary structure which is carefully washed and freed from all dirt and other foreign matter. The sleeve 32 and plug 40 are then similarly washed and are positioned in the casing 26 just before the unitary structure is secured to the compressor. Since no brazing operations or the like are required in fastening the inner parts of the intake muffler 20 in place, it is possible to clean the same just prior to its assembly and the assembly operations are of such character that they will not result in a deposit of any dirt within the muffler. This is particularly important in the case of refrigerating machines which are made in large scale production, since the precautions required to assure cleanliness of the interior of the intake muffler are fairly simple. It is necessary to take such precautions since if any dirt is allowed to enter the refrigerating system it will be carried into the compressor and may result in causing faulty operation of the valves or even scoring of the compressor cylinder.

The fluid passages formed by the indentations 35 in the sleeve 32 act on the fluid passing therethrough in the same manner as a pipe having orifices located at each end thereof. A pipe is more effective in damping out vibratory audible sound waves in a fluid passing therethrough than is an orifice especially as applied to an intake muffler since the pipe forms a fluid column of relatively high inertia which absorbs the energy of the sound Waves resulting from the opening of the inlet valve as explained above. As a consequence, it is desirable to minimize the orifice effect in order that at least a major portion of the pressure drop in the muffler will occur in the pipe portion thereof in order that the pressure drop within the mufiler shall be most effectively utilized to minimize the transmission of sound.

In Fig. 5, I have illustrated a modified form of cylindrical sheet metal sleeve 45 which may be substituted for the sheet metal sleeve 32 in the muffler shown in Figs. 1 and 2 and which is arranged to minimize the orifice effect of the muffier passages on fluids passing therethrough. In this form of my invention, a muffler is provided which includes an enclosure, such as 26 in Fig. 2, forming an elongated muflling passage having an inlet and an outlet at the opposite ends thereof, the central portion of the passage being substantially uniform in cross section. The ends of the passage adjacent the inlet and outlet are enlarged and these enlarged ends 48 and 49 are connectedto the central portion of the passage by tapering portions 5l and 52 which minimize the orice effect of the passage.

In the embodiment of my invention illustrated in Fig. 5, the cylindrical sheet metal sleeve 45 is punched, or otherwise formed, from a sheet of suitable sheet metal such as sheet steel and then bent in the form of a cylinder with the longitudinal edges thereof arranged in spaced relation. The sleeve 45 is given a diameter slightly larger than the interior diameter .of the casing 26 in which it is fitted so that the sleeve will be somewhat compressed upon its insertion within the casing. Consequently, the sleeve 45 resiliently engages the interior walls of the casing and is thus maintained in position therein. Even when the sleeve 45 is compressed within the casing, however, the longitudinal edges thereof are maintained in spaced relation in order to provide an outlet for liquid lubricant as heretofore described with respect to the sleeve 32.

A series of three symmetrically arranged longitudinal indentations or grooves 46 are formed in the outer surface of the sleeve 45 and extend substantially throughout the length thereof. The indentations 46 include elongated central portions 41 of substantially uniform cross section and enlarged upper and

lower end portions

48 and 49, respectively. The enlarged upper end portions 48 communicate with the inlet openings 36 formed in the casing 26. Elongated substantially elliptical openings or ports 50 are formed in the sleeve 45 in the side walls of the enlarged lower end portions 49 and form outlets for the passages 46. The adjacent ends of the central portions 41 are connected to the adjacent

enlarged Vend portions

48 and 49 by tapered portions 5! and 52, respectively, of the indentations 46. The tapered portions 52 are made somewhat longer than the tapered portions 5I since the fluid passing through the openings 50 changes direction and moves upwardly through a chamber 53 formed in the interior of the sleeve 45 and surrounded thereby and, as a consequence, greater precaution must be taken to prevent an undue pressure drop at these openings. The openings 50 are made elongated in form in order to minimize the pressure drop in the fluid passing therethrough.

The sleeve 45, described above, is inserted in a cylindrical casing such as the casing 26 shown in Fig. 2, and a sheet metal cup-shaped plug 4U shown in Fig. 4 is inserted in the lower end of the sleeve in order to close the same and aid in maintaining .the sleeve in position within the casing. The sleeve 45 is provided with a hole 54 in the lower portion thereof which registers with the hole 4| formed in the plug 40. A suitable screw 43 may be positioned in the holes 54 and 40 and a registering hole formed in the casing 26, the inner end of the screw being threaded in a tapped hole formed in the frame of the driving motor Il.

Vaporized refrigerant enters the muffler, described above, through the inlet openings 36 in the casing 26 and passes downwardly through the elongated fluid mullling passages formed by the indentations 46 in the sleeve 45 and the co-operating adjacent portions of the casing 26. The vaporized refrigerant then passes through the openings 50 into the chamber 53 formed within the sleeve 45 and passes upwardly therethrough to the outlet opening 36 in the cap 21. Since the

portions

48 and 49 of the indentations 46 adjacentk the openings 36 and 56, respectively, are enlarged and since the portions of the indentations connecting the central portions 41 and the

enlarged portions

48 and 49 are tapered, the principal pressure drop in the fiuid passing through the passages formed by the indentations 46 occurs in the elongated central portions 41 thereof which have substantially the effect of elongated pipes on the fluid. The pressure drop of the fluid passing through the passages formed by the indentations 46 is thus most effectively utilized to minimize the transmission of sound waves therethrough. At the same time a relatively long reverse-flow fluid mufiling path is formed between the inlets 36 of the muffler and the outlet 38 thereof. Since the vaporized refrigerant passing through the muffler passes downwardly throughout substantially the entire length of the sleeve 45 and then upwardly throughout the same distance in the chamber 53 it traverses a path of substantially twice the length of the sleeve and a relatively long path is thus provided while the length of the muffler structure is minimized.

In the operation of the refrigerating machine, described above, vapor-ized refrigerant, such as sulphur dioxide, is compressed in the refrigerant compressor i and is discharged therefrom through a suitable discharge valve and passes through the discharge conduit 22 to the discharge muffler 25 which is secured to the lower end of the discharge conduit 22. The compressed gaseous refrigerant leaving the discharge mufiler 25 is conveyed therefrom through a conduit 55 to the natural draft air cooled condenser I6 which surrounds the casing I5. The condenser i6 includes cylindrical inner and outer sheets of steel or the like 58 and 5I having complementary indentations 58 and 59, respectively, formed therein. The complementary indentations 58 and 59 denne a refrigerant circulatory passage 60 therebetween which extends about the condenser IS. The refrigerant circulatory passage 69 is preferably divided into upper and lower sections which are joined together in series by a U-shaped conduit (I. The condenser I6 thus formed is supported on a series of radial sheet metal heat conducting fins 62 which extend between the outer side wall of the casing I5 and the inner wall of the condenser IB. Compressed gaseous refrigerant is supplied to the refrigerant circulatory passage 8G of the condenser I6 by the conduit 55 and in flowing through the passage B is liquefied by the transfer of heat therefrom through the surrounding cooling air which circulates upwardly over the surfaces of the condenser IB and fins 62 due to natural draft.

The refrigerant liquefied in the condenser I6 is discharged therefrom through a conduit 62' through which it flows through the flow controlling float valve II. Liquid refrigerant is supplied from the float valve I'I through a liquid line 53 to refrigerant circulatory passages 64 of the flooded type sheet metal evaporator I8. The refrigerant circulatory passages 64 of the evaporator IB are formed by a series of corrugations in the outer sheet of the evaporator and these passages communicate below the normal liquid level therein with a cylindrical longitudinal header 85 formed in the upper portion of the evaporator. The header 65 is maintained about half full of liquid refrigerant and the refrigerant circulatory passages 64 of the evaporator are thus flooded with liquid refrigerant. The liquid refrigerant in the passages 64 of the evaporator I8 is vaporized by the absorption of heat from the compartment in which the evaporator is located and the refrigerant thus vaporized is accumulated in the header 65 above the level of the liquid refrigerant therein. The vaporized refrigerant thus accumulated in the header 65 is returned to the interior of the casing I5 through a conduit 66 which communicates with the header G5 above the normal level of the liquid refrigerant therein. The interior of the casing I5 is thus maintained at a comparatively low pressure being approximately the same as that prevailing within the evaporator 34. The vaporized refrigerant in the casing I5 is drawn into the compressor I0 through the intake muffler 20, described above, and the cycle is repeated and continued until the temperature prevailing in the compartment in which the evaporator I8 is located is lowered to a desired value.

Although I have illustrated two embodiments of my invention in connection with a household type refrigerating machine, I do not desire my invention to be limited to the particular construction shown and described and I intend, in the appended claims, to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A muffler for a refrigerating machine or the like comprising a tubular casing, a cap extending across one end of said casing and closing the same, a tubular resilient split sleeve removably positioned in said casing and resiliently engaging the inner walls thereof, said sleeve being provided with a plurality of longitudinal indentations formed in the outer surface thereof, said indentations and the adjacent portions of said casing co-operating to define a series of extended fluid muflling passages therebetween, and means including a plug removably inserted in the end of said sleeve opposite said cap for closing said last mentioned end of said sleeve and for retaining the same in position in said casing.

2. A muffler for a refrigerating machine or the like comprising a tubular casing, a. cap extending across one end of said casing and closing the same, a sheet of metal of tubular form constituting an inner sleeve removably positioned in said casing, said inner sleeve resiliently engaging the inner walls of said tubular casing, the longitudinal edges of said sheet of metal being arranged in spaced relation, said sleeve being provided with a plurality of longitudinal indentations formed in the outer surface thereof, said indentations and the adjacent portions of said casing co-operating to dene a series of extended fluid mufliing passages therebetween, and means including a plug removably inserted in the end of said sleeve opposite said cap for closing said last mentioned end of said sleeve and for maintaining the same in position in said casing.

3. A muffler for a refrigerating machine or the like comprising a cylindrical casing, a cap extending across one end of said casing and closing the same, a cylindrical sheet metal sleeve removably positioned in said casing and engaging the inner walls thereof, said sleeve being provided with a, plurality of grooves formed in the outer surface thereof and extending substantially throughout the length thereof, said grooves and the adjacent portions of said casing co-operating to define an extended fluid muffling passage therebetween, and means including a cup-shaped sheet metal plug removably inserted in the end of said sleeve opposite said cap and with the open end of said plug presented away from the adjacent end of said sleeve for closing said end of said sleeve and for retaining the same in position in said casing.

4. A muflier for a refrigerating machine or the like comprising a cylindrical casing, a cap extending across one end of said casing and closing the same, said cap having an outlet opening formed therein, a cylindrical sheet metal sleeve removably positioned in said casing and engaging the inner walls thereof, said sleeve being provided with a. plurality of grooves formed in the outer surface thereof and extending substantially throughout the length thereof, said grooves and the adjacent portions of said casing co-operating to define an extended fluid muilling passage therebetween, said casing having an inlet opening formed therein communicating with said passage and said sleeve having a port formed therein lcommunicating with said passage and with the interior of said sleeve, and means including a plug removably inserted in the end of said sleeve opposite said cap for closing said last mention-ed end of said sleeve and for retaining the same in position in said casing.

5. A muffler for a refrigerating machine or the like comprising a cylindrical casing, a cap extending across one end of said casing and closing the same, said cap having an outlet opening formed therein, a resilient sheet of metal forming a cylindrical sleeve removably positioned in said casing and resiliently engaging the inner walls thereof, the. longitudinal edges of said sheet of metal being arranged in spaced relation and defining an oil drainage passage therebetween, said sleeve being provided with a plurality of longitudinal indentations formed in the outer surface thereof, said indentations and the adjacent portions of said casing co-operating to define a series of extended fluid muffling passages therebetween, said casing having a series of inlet openings formed therein communicating with said passages adjacent the ends thereof and said sleeve having a series of elongated openings formed therein communicating with the opposite ends of said passages, and means including a cupshaped sheet metal plug removably inserted in the end of said sleeve opposite said cap and with the open end thereof presented away from the adjacent end of said sleeve for closing the end of said sleeve and for retaining the same in position in said casing.

6. A muffler for a refrigerating machine or the like comprising a tubular casing, a cap extending across one end of said casing and closing the same, means for closing the opposite end of said casing, a tubular sheet metal sleeve positioned in said casing and engaging the inner walls thereof, said sleeve having a plurality of grooves formed in the outer surface thereof and extending throughout substantially the entire length thereof, said mufller being provided with an inlet and an outlet, said inlet communicating with said grooves adjacent one end of said sleeve and said outlet being located adjacent said one end of said sleeve and communicating with a chamber formed by said sleeve and surrounded thereby, and means including a series of ports formed in said sleeve and communicating with said grooves adjacent the ends thereof opposite said inlet for connecting said grooves and said chamber in series, said grooves and said chamber forming an extended reverse-dow fluid muffling path between said inlet and said outlet of substantially twice the length of said sleeve.

7. A mufiier for a refrigerating machine or the like comprising a tubular casing, a cap extending across one end of said casing and closing the same, means for closing the opposite end of said casing, a tubular sheet metal sleeve positioned in said casing and engaging the inner walls thereof, said sleeve having a plurality of longitudinal indentations formed in the outer surface thereof, said muflier being provided with an inlet and an outlet, said inlet communicating with said grooves adjacent one end of said sleeve and said outlet being located adjacent said one end of said sleeve and communicating with a chamber formed by said sleeve and surrounded thereby, and means including a series of ports formed in said sleeve and communicating with said indentations adjacent the ends thereof opposite said inlet for connecting in series said indentations and said chamber, said indentations and said chamber forming an extended reverse-flow fluid muifling path between said inlet and said outlet of substantially twice the length of said sleeve.

8. A muffler for a refrigerating machine or the. like comprising a cylindrical casing, a cap extending across one end of said casing and closing the same, said cap having an outlet opening formed therein, means for closing the opposite end of said casing, a cylindrical sheet metal sleeve positioned in said casing and engaging the inner walls thereof, said sleeve. having a plurality of grooves formed in the outer surface thereof and extending throughout substantially the entire length thereof, said casing being provided with a series of inlet openings adjacent the end thereof on which said cap is positioned, said inlet openings communicating with said grooves, and means including a series of openings in said sleeve communicating with said grooves adjacent the ends thereof opposite said inlet openings for connecting in series said grooves and a chamber formed by said sleeve and surrounded thereby, said grooves and said chamber forming an extended reverse-flow uid muiliing path between said inlet openings and said outlet opening of substantially twice the length of said sleeve.

9. A muffler for a refrigerating machine or the like comprising a cylindrical casing, a cap extending across one end of said casing and closing the same, said cap having an outlet opening formed therein, means for closing the opposite end of said casing, a cylindrical sheet metal sleeve positioned in said casing and engaging the inner walls thereof, said sleeve having a plurality of longitudinal indentations formed in the outer surface thereof and extending throughout substantially the entire length thereof, said casing being provided with a series of inlet openings communicating with said indentations adjacent said cap, and means including a series of elongated openings formed in said sleeve and communicating with said indentations adjacent the ends thereof opposite said inlet openings for connecting in series said indentations and a chamber formed by said sleeve and surrounded thereby, said indentations and said chamber forming an extended reverse-flow muflling path between said inlet and said outlet of substantially twice the length of said sleeve.

10. A muffler for a refrigerating machine or the like comprising a cylindrical casing, a cap extending across one end of said casing and closing the same, a cylindrical sheet metal sleeve removably positioned in said casing and engaging the inner walls thereof, said sleeve being provided with a series of longitudinal indentations formed in the outer surface thereof, said indentations and the adjacent portions of said casing cooperating to define a series of extended fluid mufliing passages therebetween, the central portions of said indentations being elongated and substantially uniform in cross section, said muflier being provided with inlets and outlets communicating with the opposite ends of said indentations, said indentations having enlarged portions adjacent said inlets and outlets and having tapered portions extending between the adjacent ends of said enlarged portions and said central portions to minimize the orifice eiect of said passage on fluids passing therethrough.

11. A muiiier for a refrigerating machine or the like comprising a cylindrical casing, a cap extending across one end of said casing and closing the same, said cap having an outlet opening formed therein, means for closing the opposite end of said casing, a cylindrical sheet metal sleeve positioned in said casing and engaging the inner Walls thereof, said sleeve being provided with a plurality of longitudinal indentations formed in the outer surface thereof and co-operating with the adjacent portions of said casing to dene a series of extended fluid muffling passages therebetween, the central portions of said indentations HARLEY H. BIXLER.