US3838749A

US3838749A - Pulse noise reducer

Info

Publication number: US3838749A
Application number: US00332570A
Authority: US
Inventors: H Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-02-15
Filing date: 1973-02-15
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01

Abstract

Flow of gas from a pulsating pressure source is conducted through a muffler device to remove undesirable sound frequencies, cool the gas and substantially prevent back pressure flow between pressure pulsations of the gas. The gas is conducted through a baffling zone in the muffler formed by baffle plates having crescent-shaped openings through which flow of the gas is limited. The openings render the baffle plates effective as acoustical wave filters and impart a spin to the gas conducted therethrough.

Description

United States Patent 11 1 Johnson 1451 Oct. 1, 1974 I PULSE NOISE REDUCER [76] Inventor: Howard R. Johnson, 3300 Mt. Hope Rd., Grass Lake, Mich. 49240 221 Filed: Feb. 15,1973

21 App1.No.:332,570

[52 US. Cl 181/56, 181/57, 181/63 [51 Int. Cl. F0ln 1/08 [58] Field 61 Search 181/40, 46, 49, 56-58,

[56] References Cited UNITED STATES PATENTS 1,304,096 5/1919 Redeker et al. 181/49 2,566,939 9/1951 Johnson 181/69 X 2,914,133 11/1959 Johnson 181/63 X FOREIGN PATENTS OR APPLICATIONS 5/1930 Australia 181/56 Primary Examiner-Richard B. Wilkinson Assistant ExaminerJohn F. Gonzales Attorney, Agent, or Firm-Clarence A. OBrien; Harvey 13. Jacobson 5 7 ABSTRACT Flow of gas from a pulsating pressure source is conducted through a muffler device to remove undesirable sound frequencies, cool the gas and substantially prevent back pressure flow between pressure pulsations of the gas. The gas is conducted through a baffling zone in the muffler formed by baffle plates having crescent-shaped openings through which flow of the gas is limited. The openings render the baffle plates effective as acoustical wave filters and impart a spin to the gas conducted therethrough.

8 Claims, 4 Drawing Figures PULSE NOISE REDUCER somewhat reduced by the muffler because of backpressure flow. Further, such muffler devices are often considerably expensive to manufacture because of structural and material requirements resulting from heat transfer and sound absorption problems.

It is therefore an important object of the present invention to provide a muffler device for pulsating pressure generators such as two-cycle combustion engines and air conditioning compressors that have severe pressure pulsating problems, whereby the reduction in operating efficiencies of such pressure generatdrs is minimized and more economical handling of noise and heat transfer problems is made possible.

In accordance with the present invention, an inflow of gas from a pulsating pressure source is conducted through an expansion chamber to a baffling zone in which a plurality of axially spaced baffle members limit flow of the" gas along parallel flow paths established by aligned openings in the baffle members. The openings are formed by pairs of confronting crescent-shaped cuts in the radially outer portions of the baffle members rendering them effective as acoustical wave filters. The crescent-shaped openings also impart a spin to the gas thereby producing a cooling action. Flow through the openings in the baffle members thereby accelerates with minimal back pressure flow and shock waves.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.

FIG. 1 is a perspective view of a muffler device constructed in accordance with the present invention.

FIG. 2 is a longitudinal section view taken substantially through a plane indicated by section line 2.2 in FIG. 1.

FIG. 3 is another longitudinal section view in a plane perpendicular to that of FIG. 2, as indicated by section line 3-3.

FIG. 4 is a transverse section view taken substantially through a plane indicated by section line 4-4 in FIG. 2

Referring now to the drawings in detail, FIG. 1 shows the muffler device of the present invention generally denoted by reference numeral 10. The muffler device includes a generally cylindrical housing 12 made of a metal such as aluminum having the desired strength and corrosion resistant properties for the particular installation. Opposite axial ends of the housing are closed by

circular end walls

14 and 16 as shown in FIGS. 2 and 3. An opening 18 is formed in the housing 12 adjacent the end wall 14 to receive an inlet adapter 20 that is held assembled on the housing by a pair of fastener bolts 22 extending transversely through the housing. An inlet passage 24 within the adapter 20 thus con ducts an inflow of gas from a pulsating pressure source into an inlet chamber 26 within which. volumetric ex pansion of the gas occurs.

The inlet chamber conducts the gas axially along the housing into a baffling zone generally referred to by reference numeral 28, within which a plurality of axially spaced circular baffle plates 30 are disposed. Each of the baffle plates is formed with aligned openings 32 establishing a plurality of parallel axial flow paths for the gas which exits from the housing through a tubular outlet 34 fixed to the end wall 16 in radially offset relation to the longitudinal axis of the housing as more clearly seen in FIG. 2.

The baffle plates 30 are supported on a central bolt member 36 and are axially spaced from each other and from the end wall 16 by spacer sleeves 38 also carried on the bolt member 36. The circumferential edges of the baffle plates form a reasonably close fit with the internal cylindrical surface of the housing so as to confine flow of gas through the openings 32. While the outer head 40 of the bolt 36 engages the end wall 16, the inner threaded end portion 42 projects through the central opening in the first baffle plate 30 and threadedly receives a bracket element 44 which abuts the baffle plate as shown in FIGS. 2 and 3 to clamp it against a spacer sleeve 38. The bracket element 44 is supported in axially spaced relation to the end wall 14 by a pair of supporting bolts 46 which extend axially through the inlet chamber 26 in perpendicular spaced relation to the bolts 22. The supporting bolts 46 are connected to the flange portions 48 of the bracket element 44 as shown in FIG. 2. Thus the bracket element 44 and bolts 46 cooperate with the central supporting bolt 36 to structurally support the baffle plates internally of the housing as well as to separate the inlet chamber and baffling zone in such a manner as to reduce manufacturing costs and facilitate assembly or disassembly of parts for repair or maintenance purposes.

An important aspect of the invention resides in the shape, position, flow area and associated geometry of the openings 32 in the baffle plates 30 whereby the baffle plates accelerate the flow of gas, act as acoustical filters to remove offending noise frequencies and function as a heat exchanger to cool the gas. The muffler device 10 is thereby effective to reduce undesirable pulsations and/or noise associated with exhaust gas from two-cycle, internal combustion engines, or to prevent excessive oscillations in cooling coils of air conditioning systems produced by the pulsating outflow from a sealed compressor.

As shown in FIG. 4, the openings 32 are in the form of a plurality of pairs of confronting crescent-shaped cuts or apertures in the baffle'plates circumferentially spaced from each other by equal amounts at the same radial distance from the longitudinal axis of the housing 12. As a result of this configuration, a spinning motion is imparted to the gas. The total flow area of the openings is matched to the volumetric inflow of gas through the inlet passage 24 so as to produce a sufficient decrease in its temperature to cause a change in state or condensation of some vapor components such as steam in the inflowing gas. This cooling action results from both the expansion of the gas in the inlet chamber 26 and the high velocity spin imparted thereto by the baffle plates. The flow area of the openings will permit acceleration of the gas flow but the crescent shape, size and location of the openings will limit back flow and shock waves. This will enhance scavenging of the combustion chambers when the muffler device receives the exhaust from an internal combustion engine as the source of pressure pulsating gas. The cooling action by reducing the sound velocity through the gas and the heat transfer problems, enables one to more easily design the muffler device to satisfactorily meet given installational requirements.

The crescent shape of the openings 32 and the associated geometrical relationships for a given installation, necessary to produce the beneficial results of the pres ent invention, are obtained from the plotting of lines of force in transverse acoustical wave fields in the plane of the baffle plates corresponding to sound wave propagation through the gas in the axial passage of the baffling zone 28. The crescent shaped openings 32 substantially occupy the space between the lines of force plotted so as to conduct gas flow without interference with longitudinal sound wave propagation associated with the transverse wave pattern except at the cut-off frequencies designed to correspond with the undesirable or offending frequencies to be removed. Thus, the

baffle plates will permit accelerated flow in the outflow direction with minimal back flow of gases that would otherwise prevent scavenging. Plotting of the transverse wave patterns was based on wave transmission theory commonly applied to electromagnetic wave transmission through circular wave guides in which transverse electric wave patterns are plotted. By utilizing this well known electromagnetic wave analysis procedure, for the sound wave transmission problem dealt with by the present invention, not only an acoustical filter or wave trap effect was obtained, but high speed spin of the gas unexpectedly developed as hereinbefore referred to.

For a 2-cycle, internal combustion engine operating at 6,000 RPM, approximate dimensional values for the muffler device found suitable in accordance with the present invention are as follows:

L 6 inches R 1.00 inch R 0.625 inch r 0.25 inch r,- 0.15 inch S /32 inch Number of pairs of openings 32 5 ln the foregoing installation, the muffler device 10 accounted for an approximately 35 percent increase in engine speed as compared to operation of the engine with its original standard muffler.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. In a muffler device to which gas is supplied from a pulsating pressure source, an elongated housing having a longitudinal axis and enclosing a flow passage for said gas including an expansion chamber and a baffling zone, and baffle means mounted within the baffling zone for establishing a plurality of parallel flow paths radially outwardly of said longitudinal axis, said baffle means including a plurality of baffle members blocking flow radially inwardly through the flow passage and having aligned openings through which flow of said gas is accelerated along said parallel flow paths, end walls closing opposite ends of the housing, supporting means extending from one of the end walls through the baffling zone on which the baffle members are mounted. and spacing means interconnecting the supporting means with the other of the end walls within the expansion chamber for holding the baffle members assembled on the supporting means.

2. The combination of claim 1 including inlet means extending transversely from the housing adjacent said other of the end walls.

3. The combination of claim 1 wherein said spacing means includes a bracket secured to the supporting means in abutment with one of the baffle members, and fastener means extending through the expansion chamber between the bracket and the other of the end walls for holding the bracket assembled.

4. In a muffler device to which gas is supplied from a pulsating pressure source, an elongated housing having a longitudinal axis and enclosing a flow passage for said gas including an expansion chamber and a baffling zone, and baffle means mounted within the baffling zone for establishing a plurality of parallel flow paths radially outwardly of said longitudinal axis, said baffle means including a plurality of baffle members blocking flow radially inwardly through the flow passage and having aligned openings through which flow of said gas is accelerated along said parallel flow paths, end walls closing opposite ends of the housing, supporting means extending from one of the end walls through the baffle zone on which the baffle members are mounted, spacing means interconnecting the supporting means with the other of the end walls within the expansion chamber for holding the baffle members assembled on the supporting means, inlet means extending transversely from the housing adjacent said other of the end walls, and fastener means extending through the expansion chamber transversely of the spacing means for holding the inlet means assembled on the housing.

5. The combination of claim 4 wherein said openings are confronting pairs of crescent-shaped cuts in the baffle members.

6. In a muffler device to which gas is supplied from a pulsating pressure source, an elongated housing having a longitudinal axis and enclosing a flow passage for said gas including an expansion chamber and a baffling zone, baffle means mounted within the baffling zone for establishing a plurality of parallel flow paths radially outwardly of said longitudinal axis, end walls closing opposite ends of the housing, supporting means extending from one of the end walls through the baffling zone on which the bafi'le members are mounted, spacing means interconnecting the supporting means with the other of the end walls within the expansion chamber for holding the baffle members assembled on the supporting means, inlet means extending transversely from the housing adjacent said other of the end walls, and fastener means extending through the expansion chamber transversely of the spacing means for holding the inlet means assembled on the housing.

7. The combination of claim 6 wherein said openings impart a spinning motion to the gas conducted therethrough and render the baffle members operative as acoustical wave filters.

having aligned openings through which flow of said gas is accelerated in non-intersecting flow streams along said parallel flow paths, said openings including arcuate pairs of apertures having centers of curvature radially spaced from the longitudinal axis for imparting a spinning motion to the gas conducted therethrough and rendering the baffle members operative as acoustical wave filters.

Claims

1. In a muffler device to which gas is supplied from a pulsating pressure source, an elongated housing having a longitudinal axis and enclosing a flow passage for said gas including an expansion chamber and a baffling zone, and baffle means mounted within the baffling zone for establishing a plurality of parallel flow paths radially outwardly of said longitudinal axis, said baffle means including a plurality of baffle members blocking flow radially inwardly through the flow passage and having aligned openings through which flow of said gas is accelerated along said parallel flow paths, end walls closing opposite ends of the housing, supporting means extending from one of the end walls through the baffling zone on which the baffle members are mounted, and spacing means interconnecting the supporting means with the other of the end walls within the expansion chamber for holding the baffle members assembled on the supporting means.

6. In a muffler device to which gas is supplied from a pulsating pressure source, an elongated housing having a longitudinal axis and enclosing a flow passage for said gas including an expansion chamber and a baffling zone, baffle means mounted within the baffling zone for establishing a plurality of parallel flow paths radially outwardly of said longitudinal axis, end walls closing opposite ends of the housing, supporting means extending from one of the end walls through the baffling zone on which the baffle members are mounted, spacing means interconnecting the supporting means with the other of the end walls within the expansion chamber for holding the baffle members assembled on the supporting means, inlet means extending transversely from the housing adjacent said other of the end walls, and fastener means extending through the expansion chamber transversely of the spacing means for holding the inlet means assembled on the housing.

8. In a muffler device to which gas is supplied from a pulsating pressure source, an elongated housing having a longitudinal axis and enclosing a flow passage for said gas including an expansion chamber and a baffling zone, and baffle means mounted within the baffling zone for establishing a plurality of parallel flow paths radially outwardly of said longitudinal axis, said baffle means including a plurality of baffle members blocking flow radially inwardly through the flow passage and having aligned openings through which flow of said gas is accelerated in non-intersecting flow streams along said parallel flow paths, said openings including arcuate pairs of apertures having centers of curvature radially spaced from the longitudinal axis for imparting a spinning motion to the gas conducted therethrough and rendering the baffle members operative as acoustical wave filters.