US3612214A

US3612214A - Pressure release safety industrial air exhaust silencer

Info

Publication number: US3612214A
Application number: US91125A
Authority: US
Inventors: Leland Francis Blatt; Frank H Wiesenhofer
Original assignee: Individual
Current assignee: ISI MANUFACTURING Inc A MI CORP
Priority date: 1970-11-19
Filing date: 1970-11-19
Publication date: 1971-10-12
Anticipated expiration: 1988-10-12

Abstract

An air exhaust silencer comprises a barrel which has a piston head, the barrel is contained for reciprocation within a cylinder and is normally retained in the cylinder in a retracted position so as to permit air exhaust through the silencer structure which embodies a pair of gas permeable frequency distorters adapted to muffle the noise of the exhaust air to below a predetermined maximum noise level; the barrel of the silencer is provided with a plurality of relief ports which are in open communication with the barrel retaining cylinder, mechanical releasable retaining means are employed to normally retain the barrel in the retracted position, however, upon buildup of back pressure in the silencer assembly, due to clogging of the gas permeable members of the silencer, the increased air pressure through the silencer will act to move the barrel of the silencer out of the cylinder overcoming the force of the retaining means to expose the relief ports of the barrel to the atmosphere to thereby permit air pressure to bypass said clogged gas permeable members of the silencer for direct passage to the atmosphere.

Description

United States Patent [72] Inventors Appl. No. 91,125-

[22] Filed Nov. 19, 1970 [45] Patented Oct. 12, 1971 [54] PRESSURE RELEASE SAFETY INDUSTRIAL AIR EXHAUST SILENCER 12 Claims, 4 Drawing Figs.

[52] US. Cl 181/37, 181/45,181/65 [51] Int. Cl F01n1/10, FOln 1/20,F01n 3/00 [50] Field of Search 181/36-38, 45, 36.1,47, 47.1, 72, 64.2, 65

[56] References Cited UNITED STATES PATENTS 1,807,512 5/1931 Culp 181/65 2,729,234 1/1956 Stevenson l8l/47.1

3,129,078 4/1964 Hobbs 181/45 X 3,339,668 9/1967 Trainor 18 l/36.1

FOREIGN PATENTS 1,372,464 8/1964 France 181/65 Primary Examiner-Robert S. Ward, Jr. Attorney-Cullen, Settle, Sloman & Cantor ABSTRACT: An air exhaust silencer comprises a barrel which has a piston head, the barrel is contained for reciprocation within a cylinder and is normally retained in the cylinder in a retracted position so as to permit air exhaust through the silencer structure which embodies a pair of gas permeable frequency distorters adapted to muffle the noise of the exhaust air to below a predetermined maximum noise level; the barrel of the silencer is provided with a plurality of relief ports which are in open communication with the barrel retaining cylinder, mechanical releasable retaining means are employed to normally retain the barrel in the retracted position, however, upon buildup of back pressure in the silencer assembly, due to clogging of the gas permeable members of the silencer, the increased air pressure through the silencer will act to move the barrel of the silencer out of the cylinder overcoming the force of the retaining means to expose the relief ports of the barrel to the atmosphere to thereby permit air pressure to bypass said clogged gas permeable members of the silencer for direct passage to the atmosphere.

PATENTEDHBHZIQH 3.612.214

LELAND FRANCIS BLATT ANK H. WIESENHOFE ATTORNEYS PRESSURE RELEASE SAFETY INDUSTRIAL AIR EXHAUST SILENCER The present application relates in part to the air silencer structure disclosed in applicant's copending application, Ser. No. 81,051 filed Oct. 15, 1970 for AIR EXHAUST SILENCER and comprises a further improvement thereof.

BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to mufi'lers or silencer structures and more in particular to an air exhaust silencer.

These types of silencers are incorporated in industrial applications for air valve outlets or venturis on air operated tools, pneumatic presses and the like.

The silencer of the present invention has a barrel-type housing providing an inlet for attachment to a respective air exhaust. The housing contains one or more frequency distorters made of porous material, such as sintered bronze, ceramic or the like, and in certain applications may also include a frequency modulator of foam material disposed between two adjacent frequency distorters.

lt is evident that with the type of porous material, used for the frequency distortion and frequency modulator members of the silencer, if the air exhaust lines to which the silencer is attached carry any foreign material, such as debris, scale, hard grease, etc. the foreign material conveyed by the stream of air will be carried into the silencer and eventually clog the porous frequency distorter members, which act as a filter letting only air through at a certain flow rate, the foreign material carried by the airflow being caused to adhere to the surface of the porous frequency distorter members. Clogging of the porous members through which the exhaust air is caused to pass, of course, considerably decreases the flow efficiency through the silencer by creation of back pressure. 1

In most ordinary applications, this will present no great problem other than the possible slow down of the operating equipment to which the silencer is attached. However, in some particular applications, such as in clutch or brake valve applications for a pneumatic press, clogging of the porous members in the silencer will eventually cause the valve to malfunction and, thus, the brake or clutch of the press cannot be operated properly, with the result that the press ram would automatically continue to reciprocate without the usual intermittent stop and start requirement of the ram. This, of course, creates a considerable safety hazard and may also result in costly damage to the machinery.

In view of the foregoing, the present invention provides an improved, pressure release, safety mechanism for this type of silencer which is effective to maintain a constant flow rate from the exhaust. Thus, in the event that the porous members of the silencers should become severely clogged the increased airflow pressure through the silencer is effective to actuate the safety release mechanism, causing the airflow to be directly diverted to the atmosphere by bypassing the clogged porous frequency distorter members of the silencer, until such time at which the clogged porous members will have been cleaned or replaced.

The advantages of the present invention will be clearly evident from the following detailed description of preferred embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate two preferred embodiments of the .invention in which:

FIG. I is a longitudinal cross section of one embodiment thereof utilizing fluid pressure in conjunction with a shear pin to normally maintain the silencer in operating position;

FIG. 2 illustrates the arrangement of FIG. 1 in the extended position for bleeding of air directly to the atmosphere;

FIG. 3 is a cross section through a further embodiment of the present invention incorporating an extension spring in place of the shear pin to normally maintain the silencer in operating position; and I FIG. 4 illustrates the arrangement of FIG. 3 in the extended position for bleeding of the exhausted air directly to the atmosphere.

DETAILED DESCRIPTION OF THE INVENTION With reference to the drawings, particularly FIGS. land 2, this embodiment of the combined silencer and pressure relief assembly, generally indicated at 10, is composed of a cylindrical housing 12 closed by an outer end cap 14 having a pilot section 16 extending into said housing 12 and which provides the seat for a seal ring 18. The other end of the cylindrical housing 12 is closed by a port cap 20 similarly provided with a pilot portion 22 which extends into the housing [2 providing a seat for a similar seal ring 24. The two

end caps

20 and 14 are tied together by a plurality of tie rods 46, as is customary in cylinder designs of this kind.

With reference to FIG. 2, an alternate cylinder structure is illustratively shown, which may be substituted for cylinder 12, and in this instance comprises a cylindrical housing 28 having at one end an internal radial flange 30 which replaces the former end cap 14. The other end of the cylindrical member 28 is provided with a port cap 32 which is threaded into the end of the cylinder and replaces the end cap 20 of F l6. 1.

It will be understood that either cylinder design, I2 or 28, may be utilized in both embodiments of FIGS. I and 2 or 3 and 4 which ever may be more convenient or adaptable.

Still referring to FIGS. 1 and 2, the

cylinder

12, or 28, is attached to the air exhaust pipe 34 of the particular device or tool which the silencer structure is applied by means of a threaded bore 36 in

end cap

20, or 32, which provides the inlet into the silencer structure.

The

cylindrical housing

12, or 28, is adapted to receive a silencer assembly 38 composed of a cylindrical barrel 40 which outer end is supported in sliding engagement with the internal surface of the outer end cap 14, or flange 30, respectively. The inner radial surface of the outer end cap 14, or flange 30, is provided with a seal assembly 42 for sealing engagement around the barrel 40.

The inner end of the barrel member 40 is threadedly attached to the pilot end of a piston 44 adapted for reciprocation within the

cylinder

12, or 28. The piston 44 is provided with an axial aperture 45 which is coaxially aligned with inlet 36 through the

port end cap

20, or 32, to permit airflow from the exhaust pipe 34 into the barrel 40 of the silencer assembly.

It will be noted that the outer diameter of the barrel member 40 is of substantially smaller dimension than the inner diameter of the

cylinder

12, or 28, to thereby provide a radial chamber 46 between the barrel 40 and

cylinder

12 or 28, respectively.

The barrel 40 of the silencer assembly 38 is normally retained in retracted position within the cylinder I2, as shown in FIG. I, by means of one or a plurality of shear pins 48 extending through the outer end cap 14, or flange 30 respectively, and across the outer end of the barrel 40, as shown in FIG. 1. The shear pin 48 may be made of plastic material having a shear strength selected to permit only a predetermined percentage of clogging of the silencer, as explained hereafter.

The barrel 40 of the silencer assembly 38 is provided with a plurality of relief ports 50 (in this instance 4 equally radially spaced around the barrel 40 and which are normally in open communication with the radial chamber 46 and the inlet 36.

The outer end of the barrel 40 of the silencer assembly 38 retains a pair of

frequency distorter members

52 and 54, respectively, of identical construction and assembled in backto-back relationship. The

frequency distorter members

52 and 54 are of axially extending dome-shaped configuration such that the member 52 extends through the barrel 40 forwardly towards the

inlets

36 and 45 and the other member 54 extends axially outwardly of both thebarrel 40 and cylinder 12. Each of the

frequency distorter member

52 and 54 is provided with an opposed radial flange 56 and 58, respectively which are disposed in abutting relationship and retain a sealing member 60 in between them. In order to retain the

members

52 and 54 in position, the flange 56 of the member 52 abuts against an inner shoulder 62 within the barrel 40 and the other flange 58 of the other member 54 is clamped against flange 56 by means ofa lock ring 64'.

The dome-shaped

frequency distorter members

52 and 54 are made of a porous material such, as for instance, sintered bronze, ceramic or the like, having a predetermined density which varies with the particular application of the silencer assembly. Similarly, the density of the porous material of the frequency distorter member 52 may be different from that of the other frequency distorter member 54 before to obtain sequential noise reduction from the air exhaust passing through the silencer assembly 38.

In certain applications and particularly in applications where different noises having different frequencies must be absorbed by the silencer an additional noise reduction member 64 of porous nature is provided which is located between the dome-shaped

frequency distorter members

52 and 54. This member which appropriately can be called a frequency modulator, is made of a foamed urethane or any similar porous material.

In operation airflow at a known rate and speed enters the silencer assembly 38 fromthe exhaust 34 through the

inlet openings

36 and 45 for travel through the first porous frequency distorter member 52 and then through the intermediate baffle member 64 and the'outer frequency distorter member 54 to the atmosphere. The air exits through the member 54 at a greatly reduced noise level. A portion of the exhaust airflow flows through the relief ports 50 in the barrel 40 into the radial chamber 46 to maintain a constant pressure at the rear of the piston 44 to assist the shear pin or pins 48 for normally retaining the silencer assembly retracted within the

cylinder

12, or 28. The

seals

18, 24 and 42 effectively prevent escape of air pressure from the chamber 46. v

In the event the gas permeable member 52 becomes clogged after a time of operation, due to foreign substances carried by the exhaust air stream, an increased pressure buildup takes place in the silencer 40 and at the front end of the piston 44, with a simultaneous reduction in the' airflow efficiency through the silencer assembly. The increased pressure acts on the clogged surface of the inner porous member 52 as well as on the front face of the piston 44 immediately adjacent inlet 36. The increased pressure at a certain magnitude overcomes the retaining force of the shear pin 48 to break said shear pin and thus forcing the silencer assembly 38, barrel 40 and piston 44, out of the

outer cylinder

12, or 28 respectively,to the position shown in FIG. 2. By movement of the barrel 40 outwardly of the

cylinder

12, or 28, the relief ports 50 will'beexp'os ed to atmosphere, as illustrated by the position of the assembly in f FIG. 2, to thereby divert the air flow from the exhaust 34 directly to the atmosphere, bypassing the clogged porous members 5254. The pilot portion 16, or respectively flange 30, limit the outward movement of the piston 44 to prevent complete separation from the

cylinder

12, or 28.

The outwardly extended position of the silencer assembly 38 together with the increased noise level of the air escaping through the relief ports 50, immediately indicates to the, operator of the apparatus or machinery, to which the silencer assembly is attached, that the assembly must be serviced by cleaning or replacement of thepor'ous members 52-54. After this, the barrel 40 can be manually moved back into the

cylinder

12, or 28, and new shear pins will be provided to retain the barrel in the cylinder for renewed operation of the silencer assembly.

With reference now to FIGS. 3 and 4, in this embodiment of the combined silencer and pressure relief assembly identified by the numeral 100, the assembly is substantially identical to that shown in FIGS. 1 and 2, with the exception that the shear pin retaining means 48 has been omitted and replaced by the provision of a coil expansion spring 66, which is disposed in the radial chamber 46 of the

cylinder

12, or 28, between the rear end of the piston 44 and in the pilot portion 16 of the outer cap 14- (or flange 30 respectively in the alternate cylinder construction 28).

Thus, normally the spring 66 exerts a constant force'on the piston 44 to retain the barrel and piston assembly, within the cylinder in a retracted position, as shown in FIG. 3, when the silencer is operating properly. 1 i

The forece of the spring 66 is selected such, that a predetermined pressure buildup in the assembly, due to a clogged condition of the porous members of the silencer, the force of the spring 66 will be overcome, permitting the increased pressure within the assembly to move the barrel 40 outwardly of the cylinder in order to expose the relief ports 50 to the atmosphere. This position of the assembly is illustrated in FIG.

This spring loaded embodiment of the present invention has the advantage that soon after the silencer has been serviced, or a sufficient amount of excess air pressure has been blown off through relief ports 50, to reestablish normal airflow condition, the spring 66 is permitted to expand and thus automatically returns the barrel and piston assembly to the end of the cylinder for renewed operation of the silencer.

It will be appreciated from the foregoing description and in view of the detailed illustrations that the present invention hereby provides an effective, fast acting, safety release mechanism for a silencer attached to the exhaust of an air operated apparatus or device in which back pressure created by a clogged silencer would have an adverse effect on the apparatus or device.

The mechanism of the present invention is a relatively simple arrangement but, nevertheless, is immediately automatically responsive to blow off excess air pressure directly to the atmosphere bypassing the clogged silencer assembly.

Although the present invention has been described in connection with two preferred embodiments, it will be obvious that various modifications and arrangement and structural detail may be resorted to without departing from the spirit and essential characteristic of the invention as defined by the scope of the appended claims.

We claim:

1. In combination with an air exhaust silencer assembly comprising a barrel having gas permeable members disposed therein made of a porous material to permit only the passage of air therethrough; the improvement comprising: a pressure release mechanism including a cylinder having an open end, an air inlet port at the other end of said cylinder for attachment to an air exhaust; said barrel of said silencer extend ing through said open end into said cylinder and being provided with a piston at its inner end for sliding engagement within said cylinder; said barrel being further provided with at least one relief port in open communication with said inlet and with the interior of said cylinder; and means to normally retain said barrel within said cylinder under normal operating conditions of said silencer so that said relief port is positioned in- 'wardly of said cylinder; said means being effective to give at a redetermined magnitude of pressure buildup within said silencer assembly to permit said barrel to be' moved outwardlv of said cylinder by increased pressure on said piston to thereby xpose said relief port to the atmosphere.

In the combination as defined in claim 1, said retaining means comprising at least one shear pin located at the open end of said cylinder and normally extending into the path of said barrel when said barrel is in the retracted position in said cylinder; said shear pin having a predetermined shear strength adapted to be overcome at a predetermined magnitude of pressure buildup exceeding the normal rate of fluid pressure through said silencer to thereby shear said shear pin to cause said barrel to be moved out of said cylinder by increased pressure on the front of said piston.

3. In the combination as defined in claim 1, said retaining means comprising an expandable spring disposed within said cylinder around said barrel between the rear end of said piston and an internal abutment within said cylinder; said spring having a predetermined expansion force to normally retain said barrel within said cylinder adapted to be overcome by increased pressure of fluid through said silencer beyond said predetermined magnitude to thereby cause said barrel to be moved out of said cylinder against the force of said spring by increased pressure on said piston.

4. In the combination as defined in claim 1, said open end of said cylinder being defined by an end cap having a pilot portion for extension into said cylinder; said end cap being provided with an axial aperture for the extension of said barrel therethrough in sliding contact therewith and a sealing assembly disposed in said end cap for sealing engagement with the surface of said barrel.

5. In the combination as defined in claim 4, said pilot portion of said end cap being provided with a sealing member for sealing engagement against the internal surface of said cylinder.

6. In the combination as defined in claim 4, said air inlet port being defined by a port cap member having a pilot portion for extension into said cylinder; said pilot portion carrying a sealing member for sealing engagement against the internal surface of said cylinder.

7. In the combination as defied in claim 1, said open end of said cylinder comprising an internal radially extending flange having an aperture therein for sliding extension of said barrel therethrough; said internal flange carrying a sealing member adapted for sealing engagement against the external surface of said barrel.

8. In the combination as defined in claim 7, said inlet port of said cylinder being defined by a port cap member threadedly engaged within said cylinder.

9. In the combination as defined in claim 1, said barrel being of smaller external diameter than the internal diameter of said cylinder to thereby form a radial chamber between said barrel and said cylinder normally in open communication with said release port when said barrel is in normal operating position within said cylinder.

10. A pressure relief mechanism for an exhaust silencer adapted to be connected to an exhaust port of an air operated device in which said silencer comprises a cylindrical barrel having at least one gas permeable member disposed therein for passage of air therethrough from said exhaust at a predetermined pressure magnitude and flow rate, said gas permeable member being adapted to reduce the exhaust noise of the airflow through the silencer; said safety pressure relief mechanism comprising: a cylindrical housing adapted to surround said barrel, said cylindrical housing at one end having a cap member defining an air inlet coaxially aligned with said exhaust of said device, the other end of said cylindrical housing being provided with an end wall having an aperture for the extension therethrough and sliding support of said barrel for reciprocating movement, the inner end of said barrel being provided with a piston head; said piston head having a central aperture coaxially aligned with said inlet of said cylinder to permit passage of air from said exhaust into said barrel; said barrel being further provided with at least one relief port in communication with said inlet and normally in communication with the interior of said cylinder; and means to normally releasably retain said barrel in retracted position within said cylinder; said retaining means being operable at a preselected magnitude of excess pressure within said barrel to be released to permit said barrel to be moved out of said cylinder by increased pressure force on said piston.

11. In the pressure relief mechanism as defined in claim 10, said means comprising at least one shear pin disposed in the end wall of said cylinder extending into the path of the outer end of said barrel; said shear pin having a predetermined shear strength to permit shearing of said shear pin at said increased pressure at said preselected magnitude.

12. In the pressure relief mechanism as defined in claim 10, said means comprising an expansion spring disposed within said cylinder around said barrel in axial direction between said piston and said end wall of said cylinder; said spring having a predetermined expansion force notexceeding said reselected magnitude of pressure increase within said barre to permit said barrel to be moved out of said cylinder under the influence of said preselected magnitude of pressure increase to expose said relief port to the atmosphere.

Claims

1. In combination with an air exhaust silencer assembly comprising a barrel having gas permeable members disposed therein made of a porous material to permit only the passage of air therethrough; the improvement comprising: a pressure release mechanism including a cylinder having an open end, an air inlet port at the other end of said cylinder for attachment to an air exhaust; said barrel of said silencer extending through said open end into said cylinder and being provided with a piston at its inner end for sliding engagement within said cylinder; said barrel being further provided with at least one relief port in open communication with said inlet and with the interior of said cylinder; and means to normally retain said barrel within said cylinder under normal operating conditions of said silencer so that said relief port is positioned inwardly of said cylinder; said means being effective to give at a predetermined magnitude of pressure buildup within said silencer assembly to permit said barrel to be moved outwardly of said cylinder by increased pressure on said piston to thereby expose said relief port to the atmosphere.

2. In the combination as defined in claim 1, said retaining means comprising at least one shear pin located at the open end of said cylinder and normally extending into the path of said barrel when said barrel is in the retracted position in said cylinder; said shear pin having a predetermined shear strength adapted to be overcome at a predetermined magnitude of pressure buildup exceeding the normal rate of fluid pressure through said silencer to thereby shear said shear pin to cause said barrel to be moved out of said cylinder by increased pressure on the front of said piston.

12. In the pressure relief mechanism as defined in claim 10, said means comprising an expansion spring disposed within said cylinder around said barrel in axial direction between said piston and said end wall of said cylinder; said spring having a predetermined expansion force not exceeding said preselected magnitude of pressure increase within said barrel to permit said barrel to be moved out of said cylinder under the influence of said preselected magnitude of pressure increase to expose said relief port to the atmosphere.