CA1299394C - Testing containing seals - Google Patents
Testing containing sealsInfo
- Publication number
- CA1299394C CA1299394C CA000540516A CA540516A CA1299394C CA 1299394 C CA1299394 C CA 1299394C CA 000540516 A CA000540516 A CA 000540516A CA 540516 A CA540516 A CA 540516A CA 1299394 C CA1299394 C CA 1299394C
- Authority
- CA
- Canada
- Prior art keywords
- pressure
- seal
- pressure chamber
- package
- flange
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Examining Or Testing Airtightness (AREA)
Abstract
K68-002(A) ABSTRACT OF THE INVENTION
Leak detector for use in detecting defective flange-shaped seals between lid and body portions of a package. A pressure chamber is provided for isolating the external edge of the seal and applying test pressure thereto. Containment of the pressure chamber includes sealing pressure applied mechanically to the flange-shaped package seal during testing, but this sealing pressure does not affect seal testing because it is appropriately limited by a self-compensating biasing of the mechanical seal.
Leak detector for use in detecting defective flange-shaped seals between lid and body portions of a package. A pressure chamber is provided for isolating the external edge of the seal and applying test pressure thereto. Containment of the pressure chamber includes sealing pressure applied mechanically to the flange-shaped package seal during testing, but this sealing pressure does not affect seal testing because it is appropriately limited by a self-compensating biasing of the mechanical seal.
Description
~2~9394 K68-002 (A) BACKGROUND OF THE INVENTION
This invent ion relates to a novel process ~or detec-tion of leaky seals in containers and apparatus for carrying out this process. The invention is related par-ticularly to detecting leaks in packages having a flexible lid material sealed to a container body such that the resulting seal structure forms a flange-like structure on the sealed package.
Many leak-detecting machines have been suggested over the years. Some such machines utilize some met'nod of ~7if~/ Sf~fes .~ infusing air into a leaky container. One suchlPatent ,.
4,326,408 to Kanoh describes how leakage of air into a watchcase is detected. Most such apparatus, however, is used in packagin~ of food or other objects which are sealed in sterile packages. Thus U.S. Patents 2,093,429 to Foss; 3,751,972 to Hass; and 1,974,026 to Hicks show methods of testing cans. Proximity sensors are known for use in detecting movement of a container wall as seen in U.S. Patent 4,188,819. More recently Wyslotsky et al, in U.S. Patent 4,409,818 utilizes displacement sensors to detect air blown through defective seals between two plastic sheets (one a container structure, the other a lid structure) of a package.
It will be evident that the Wyslotsky device depends upon the availability of unsealed package area for effec-tive containment of test gases. Moreover, it will be noted that Wyslotsky's test pressure exerts a significant pull on the package webs and thereby tends to pull a seal open. This limits somewhat the strength of seal utilized with that apparatus.
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1~99394 5~L~ NTION
The invention provides leak detecting apparatus for use in detecting lateral lea~ls in defective seals of packages of the type wherein flange seals are ~ormed by at least one lateral bond between (a) a flexible lid part of sald package and (b) an outwardly-flared flange of a container part of said package, said apparatus having: ~1) support means to hold said package by bearing against the bottom of said flange and to provide a sealing surface; (2) a pressure chamber assembly adapted to foxm a pressure chamber about the outer edge of a said flange seal, said pressure chamber assembly comprising: (a) a housing over said lid; (b) a first interior gasket means depending from said housing to bear selectively against the top of said flanged seal as it rests on said sealing surface of said support means; (c) a second exterior gasket means spaced outwardly rom said flrst gasket means depend}ng from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface; (d) both said gasket means, the exterior edge of said package seal, and said sealing surface defining a pressure chamber isolating said outer edge of said ~lange from ambient pressure; (e) said first gasket means enclosing, and sealing from said pressure chamber, a deflection-test æone within said housing and above the non-~langed portion of said lid; and (f) sensing means in said zone to sense deflection of said lid caused by fluid flowing from said pressure chamber through said ~langed seal into said package; (3) means to move said pressure chamber assembly into and out of sealing position; and (4) means to supply test ~ : 3 B
... ~ .. .
, .
fluid to said pressure chamber.
The inven~ion also provides a pressure~chamber assembly apparatus for use in detectlng lateral leaks in defective seals of packages oi the type wherein flange seals are formed by at least one lateral bond between (1) a flexible lid part of said package and (2) an outwardly-flared flange of a container part of said package, which package is supported on means to hold said package by bearing against the bottom of said flange and means to co-operate with said apparatus to provide a sealing surface and complete a pressure chamber about the outer edge of a said flange seal; said pressure chamber assembly comprising: (a~ a housing over said lid; (b) a first interior gasket means depending from said housing to bear selectively and seal against the top of said flanged seal; ~c) a second exterlor gasket means spaced outwardly from said first gasket means depending from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface; (d) both said gasket means, the exterior edge of said package seal, adapted to define with a said sealing surface a pressure chamber within which said outer edge of said flange is isolated from ambien~ pressure; (e~
said first gasket means enclosing, and seallng from sald pressure chamber, a deflection test zone within said housing and above the non-flanged portion of sald lid; and (f) sensing means in said zone to sense deflection of said lld caused by fluld flowing from said pressure chamber through said flanged seal lnto sald package.
From another aspect, the invention provides a process for testing leaks:ln the flanged seal of a container wherein sald 1~9939~
6041~ 55 flange is foLmed of a flexible lid portion sealed to a hody portion, said process comprising the steps of: (a) isolating ~he exterior edge of said con~ainer seal in a pressure chamber formed of at least two seal means; (b) applying mechanical sealing pressure directly on said flange as part of said isolating step with a first mechanical seal meang; (c) modifying said sealing pressure of said first mechanical seal means on said flange in direc~ response to ~he pressure in said pressure chamber; (d) malntaining a substantially constant pres~ure on a second mechanical seal means; and ~e) measuring deflection o~ said lid portion as a criterion of a leak in said flanged seal.
An advantageous feature of the invention is that a gasketed seal means bearing against the sealed flange portion of the paakage, i.e., the portion of the package under test, is biased such that only a llght sealing pressure is initially applied to said flanged portion of the package to be tested. When test pressure is applied, the light sealing pressure is automaticaIly increased, e.g., by the action of the gas pressure on the sea} means bearing against the seal under test. This action malntains~the differen~tial pressure across the package seal at a sultably low level thereby avoiding both damage to the paakage seal and the sealing off;o~ leaks to be detected.
It has been found that a gasket of thls~mechanical seal means is preferably neither too soft nor too hard for optimum performanae. Shore A~durometer values o~ about 20 to 100 are preferred. This allows the~apparatus to be used with a wide varlety of p`a~ckage~s and seals without incurring any problems ~ ; 4a ~93gfl~
6~412-1655 associated with both excessive deformation of the gasket when pressure is applied and excessive rigidity of the gasket. ~ither factor, when combined with imperfec~ions in ~he quallty o~ web~
used to form the package, can result in excessively-high localized pressure on the flange and damage the seal to be tested.
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K68 002(A) The apparatus of the invent ion can be constructed in any number of configurations. A preferred con-figuration is one wherein the pressure chamber assembly surrounds a package and seals off the periphery of a flange-shaped package seal which itself surrounds the periphery of a package. In such circumstances, it is particularly desirable to have initial light-sealing pressure, (e.g. a few ounces of pressure per lineal inch of seal) exerted by the pressure chamber assembly, to be applied by a thin, resilient, sheet forming biasing means and arranged in generally annular rela-tionship with respect to the pressure chamber, and extending cantilevered (as viewed in section) outwardly from a portion of the structure, or housing, of said pressure chamber such that the sheet is forced toward the package seal by test pressure. The seal means which is to bear against the package seal is thus pushed tighter by increased pressure on the resilient sheet. The mechanical seal is thereby automatically ad~usted for air pressure which may invade the package seal under test while, at the same time, maintaining its effective sealing of the pressure chamber assembly against the package.
In the~preferred mode~of the invention, a proxi-mity sensor is centrally carried on the seal assemblyand acts to determine the position of the pressure-flexed lid of the container.
The apparatus is typically operated at a sen-sitivity such that a O.OOS to 0.010-inch movement of thF package lld~causes deflection.
The sensor~illustrated below is a linear proximity sensor available from Electro Corporation of Sarasota, Florida. It is of the type that generates a field below the sensor. When a metal object enters the : ~ :
, 9939~
K6g-002(A) field, such as a flexible aluminum lid construction, eddy currents are induced and these currents are detected by the sensor. The strength of the sensed signal is a measure of how close the metal-bearing lid is to the sensor. Other sensor means can be used which can sense the initial position of a lid and the posi-tion assumed during leak testing. Among such proximity sensors are ultrasonic position-detecting sensors, e.g., of the general type available from Polaroid Corporation of Cambridge, Massachusetts. Ultrasound detecting sensors of the type which can listen to a leak may be used as a detecting means, also. Such sen-sors are sold by American Gas & Chemical Co., Ltd. of Northvale New Jersey. It has been noted that Ultrasound detectors can be used in conjunction with the leak detectors of the invention to listen for air leaking through the lid and thereby extending the func-tion and use of the leak detectors of the invention which, in the form described herein, assume the integrity of the container and lid structure.
ILLUSTRATIVE EMBODIMENT OF THE INVENTION
In this application there is des~ribed a preferred embodiment of the invention and suggested various alternatives and modifications thereof, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can be made within the scope of the invention. The suggestions herein are selected and included for the purposes of illustration in order that others skilled in the art will more fully understand the invention and the prin-ciples thereof and will be able to modify it and embody it in a variety of forms, each as may be best suited to th~ condition of a par-icular case.
~2~9~4 K68-002(A) IN THE DRAWINGS
Figure 1 is a plan view of a lea~-detecting apparatus showing the relationship of a pressure chamber assembly to a container being tested of the invention taken along the Section 1:1 of Figure 2.
Note, however, with respect to Section 1:1, none of the structure of container appears in Figure 1.
Figure 2 is a section in elevation of a leak~
detecting apparatus of the invention showing the rela-tive position of a package being tested to a testingsensor and seal means.
Figure 3 is a schematic diagram indicating the use o~ a proximity sensor in the process of the invention.
Figure 4 is a section showing the construction of a reinforced gasket seal useful with the invention.
Figure ~ is a schematic diagram showing a calibra-tion scheme useful with the invention.
Figure 6 is an alternative dual-force seal embodi-ment of the invention.
It will be understood that the apparatus of the invention will include suitable support means for posi-tioning the container to be tested with respect to the leak-detecting means. Moreover, the air is admitted and allowed out of the system through valves and with the use of electronic controls which are commonly used in the engineering arts. These aspects of the appara-tus are not novel in themselves and are not described in detail herein. Many different versions of such control systems can be used, and they can be readily ~Z~939~
K68-002(A) selected and utilized by engineers familiar wi~h the design of pneumatically and/or electronically actuated automatic test apparatus. Normally guch apparatus wilL
be packaged in an appropriate exterior housing with whatever pneumatic and electronic controls desirable for its operation.
Referring to Figures 1 and 2, it is seen that a leak-detecting apparatus 10 comprises support means 12 for a container 14 such that container 14 is positioned directly under proximity sensor 16 centered in pressure chamber assembly 18 which is positioned to seal the flange 20 of container 14 against support means 12.
The sealing assembly will be positioned by conventional pneumatic or hydraulic prime mover which is not illustrated since such systems are well known and easily implemented by those skilled in the art. When such seal is accomplished, a pressure chamber 23 will form an annular zone around the package, but the pressure from pressure chamber 23 on the package will be limited to that exerted on the external edge of the flanged seal 20 formed by an aluminum foil lid 17 and container body 19.
Pressure chamber assembly 18 comprises an outer sealing block portion 22 as a housing and frame for the components thereof. A sealing gasket 24 is carried within block 22 and adapted to seal block 22 against container-support means 12 with whatever pressure is exerted on the seal by the prime mover. Assembly 18 further comprises an inner seal means comprising a gasket;support 25 and a sealing gasket 27 of a cast two-component polyurethane having a Shore A durometer of about~80. The gasket 27 is, in turn, mounted on gasXet support 25 which~is attached to the outer sealing block 22 by a thin, e.g., about 0.008-inch .
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' ' ' " ' ' ' ~Z~3g~
K68-002(A) thick, annular piece of beryllium copper metal. This thin metal section is a spring means 32 as will be further described below. Screws 34 hold annular sprin~
32 to the outer sealing block 22.
Inward from inner sealing block 22 is a sensor-support ring 36 fastened to the inner wall 38 of sealing block 22. Ring 36 is sealed about and holds the centrally-positioned proximity sensor 16 and also comprises spaced conduits 52 which assure that the volume 54 a~ove container 14 will be at ambient pressure maintained outside the pressure chamber. In most circumstances, atmospheric pressure will be con-venient.
Referring to Figure 2, it will be seen that an enclosed volume, in reality pressure chamber 23, is formed by sealing of the seal assembly 18 against con-tainer 14 and container support 12. Test air, typi-cally at 20 to 80 pounds per square inch pressure above atmosphere, is admitted into chamber 23 through value 'V' in conduit 60, as will be described below.
When the fluid is admitted, the pressure will tend to force its way through defects in the container seal 70 which is formed between aluminum lid member 17 and plastic container body 19. This may be an adhesive bonded-seal or a heat seal, or another seal which is intended to be substantially air tight. This test pressure bears against annular spring 32 and helps to maintain the sealing pressure of the inner sealing block 30 against flange 20 of the container even as pressure may build up in the seal itself. Sufficient compensating pressure will ~ind its way into any seal defects and, thus, such defects will not be sealed off by the inner seal.
g3~4 --lo--K68-002(A) When a container is properly positioned, as seen in Figure 2, and test pressure is applied to the edge of seal, air will be forced through defects in the seal and into container 14, forcing the lid upwardly, increasing the output signal of proximity detector 16.
In operation of the apparatus, container 14 is brought into test position on support 12. Thereupon the sealing ass-embly 18 is caused to descend into sealing position as shown in Figure 2. At this point the interior seal block 25 and its gasket 27 rest only lightly on the sealed flange portion 20 of the con-tainer. Test fiuid, usually a gas liXe air or nitrogen or helium, is used to bring chamber 23 up to test pressure. Once pressure is reached, the output of the proximity detector 16 is taken as indicative of the initial vertical position of lid 17. It is suggested that this initial reading be delayed for a very short time, e.g., 0.05 to 0.3 seconds, in order to allow the package to adapt its initial test geometry to the pressure. The actual test time will depend on the nature of a particular package. It can be less than one second (but will commonly be about 2 to 3 seconds and usually be from 1 to 6Q seconds). Continuous reading of the sensor output will be obtained as a measure of the vertical position of the lid, i.e., the position assumed as a result of any gas f]ow through seal defects into the container.
The height of the lid will be used in determining whether the seal is defective. It is convenient to have a "reject signal", e.g., a red light or buzzer or both activated on sensing of a rejected package.
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K68-002(A) In any event, the pressure chamber is depressurized, the sealing assembly is raised and the package is removed for another cycle.
Other modes of operation can also be used. For example, time could be utilized as a constant test period and the failure of the sensor output to indicate an unde-sirable upward movement of the device during th~ set time would then indicate a suitable seal.
Figure 3 illustrates schematically the sensory control of a seal integrity tester constructed according to the invention. Conventional pneumatic and electrical apparatus such as solenoid valves and pneumatic conduits are not shown in an detail because these will be understood by those skilled in the art on reading the description.
With a package 14 to be tested in position, a test button is used to initiate a test cycle. A timer 303 is set to a maximum test time. Simultaneously, a reset signal is sent to bi-stable f~lip-flop 305 via conduit 306. ~ visual indication of a suitable state of the flip-flop is sent to green light 307 via electrical con-duits 308 and 310. AIso, valve 309 is actuated via con-duits 308 and 312 to bring the sealing assembly (18 as seen in Figures 1 and 2) down to form the pressure chamber 23 around the seal to be tested.
Then, valve 313 is opened to allow gas to enter the sealing assembly. The timer is started. Then, after a 0.1 second delay 316, (in which time the mechanical shifts in package configuration due to the stresses of the pressure and sealing action may occur) the test time will be started via conduit 318. When the 0.1 second delav ~nds, ~ample-and-hold ~r-uit 317 will go to the i lZS~3~
K68--002 (A ) hold state via conduit 322. The signal to b~ held at this ti~e is a signal from sensor 16 which is indicative of the vertical position of a metal package lid. This signal level on conduit 319 from sensor 16 will be held on conduit 324 even though the line 319 signal continues to vary. The signal on conduit 322 also enables the read gate 321. Read gate 321 is used to avoid setting the flip-flop at times during chamber closure, pressuriza-tion, and other times when testing is not taking place.
If the seal under test has no leaks, the signal level on conduit 319 will remain the same as the signal level on line 324. Thus, the output signal from com-parator 323 on conduit 326 will not change and therefore will not allow a "set" command signal via conduit 329.
The logic level signal on conduit 308 will not change, and the green "OK" lamp 307 will remain on.
The timer 303 will time down to zero and terminate the test by a signal sent through conduit 331 to the sequence controls. Alternately the test can be ter-minated by a stop button 328. In ~either case both air valves 309 and 313 simultaneously operate to depressurize and open to lift the sealing assembly.
As indicated above, if the seal being tested has a leak, the distance between the lid puffed up by gas leaking into the package and the sensor will become smaller. In such a case, the signal levels on conduit 319 and conduit 324 will be different because the con-duit 319 signal voltage will increase as the lid con-tinues to rise. Comparator 323 will send a signal based on this difference through conduit 326, thereby enabling read gate 321 and causing a "set" logic com-mand to be output by bi-stable flip-flop 305. The ~e~ult~nt signal on conduit 3~8 will put out the green ' : "' ' ' . : ' ~LZ~3g4 K68-002(A) light 307 and put on the red light 3~0. The timer will normally stop at this time. The pressure chamber will be depressurized and raised.
It is important that gasket 27 be radially stable with respect to the apparatus and package. Therefore it is often advisable to reinforce the gasket with an internal support structure 40 as seen in Figure 4 wherein a polyurethane gasket 27 of Shore A durometer of about 80. The annular spring 32 is fixed to the aluminum support structure 40 and positioned against a small overlap in structure 40 at 44. V-grooves 46 are used to help hold the gasket 27 in position.
The apparatus described herein is already constructed to have a leak-sensitivity of about 0.2 cubic centimeter per second leak rate.
In addition to the features of the invention described above, it is sometimes advisable to provide a calibrating means with the apparatus as seen in Figure 5. One such calibration means can comprise a hypoder-mic needle-like conduit 502 adapted for insertion into the headspace 504 of a container 514. A small calibrated leak device 516 (of the type commerically available) controls the amount of simulated leak gas being passed into the package.
Figure 6 illustrates schèmatically another sealing assembly apparatus according to the invention. A
spring 602 is utili~ed to limit initial pressure on flange 20. However, as pressure increases in pressure zone 623, it tends to force the gasket 627 downwardly as a result of further pressure exerted on the spring by spring cap 604. The sealing pressure on gasket 627 however is independent from the mechanical sealing ~2~3~
-~4-K68-002(A) pressure exerted by the prime mover on gasket 24 via the principle annular sealing block 622. o-rings 630 and 632 provide gas seal means between the pressure zone 623 and ambient and the spring chamber 635. The rings also provide sufficient flexibility and movement to allow the differential pressure to be effective at gaskets 627 and 24.
It is further noted that the apparatus can be used in a suction mode with the "pressure chamber" having a pressure below the ambient pressure. In such a case, the deflection of the lid, indicative of a leak, would be downward.
Moreover, in the suction mode, it is possible to utilize chemical sensors to detect minute quantities of materials in the container which are sucked out and use these quantities as a criterion of leak severity.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which might be said to fall therebetween.
This invent ion relates to a novel process ~or detec-tion of leaky seals in containers and apparatus for carrying out this process. The invention is related par-ticularly to detecting leaks in packages having a flexible lid material sealed to a container body such that the resulting seal structure forms a flange-like structure on the sealed package.
Many leak-detecting machines have been suggested over the years. Some such machines utilize some met'nod of ~7if~/ Sf~fes .~ infusing air into a leaky container. One suchlPatent ,.
4,326,408 to Kanoh describes how leakage of air into a watchcase is detected. Most such apparatus, however, is used in packagin~ of food or other objects which are sealed in sterile packages. Thus U.S. Patents 2,093,429 to Foss; 3,751,972 to Hass; and 1,974,026 to Hicks show methods of testing cans. Proximity sensors are known for use in detecting movement of a container wall as seen in U.S. Patent 4,188,819. More recently Wyslotsky et al, in U.S. Patent 4,409,818 utilizes displacement sensors to detect air blown through defective seals between two plastic sheets (one a container structure, the other a lid structure) of a package.
It will be evident that the Wyslotsky device depends upon the availability of unsealed package area for effec-tive containment of test gases. Moreover, it will be noted that Wyslotsky's test pressure exerts a significant pull on the package webs and thereby tends to pull a seal open. This limits somewhat the strength of seal utilized with that apparatus.
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1~99394 5~L~ NTION
The invention provides leak detecting apparatus for use in detecting lateral lea~ls in defective seals of packages of the type wherein flange seals are ~ormed by at least one lateral bond between (a) a flexible lid part of sald package and (b) an outwardly-flared flange of a container part of said package, said apparatus having: ~1) support means to hold said package by bearing against the bottom of said flange and to provide a sealing surface; (2) a pressure chamber assembly adapted to foxm a pressure chamber about the outer edge of a said flange seal, said pressure chamber assembly comprising: (a) a housing over said lid; (b) a first interior gasket means depending from said housing to bear selectively against the top of said flanged seal as it rests on said sealing surface of said support means; (c) a second exterior gasket means spaced outwardly rom said flrst gasket means depend}ng from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface; (d) both said gasket means, the exterior edge of said package seal, and said sealing surface defining a pressure chamber isolating said outer edge of said ~lange from ambient pressure; (e) said first gasket means enclosing, and sealing from said pressure chamber, a deflection-test æone within said housing and above the non-~langed portion of said lid; and (f) sensing means in said zone to sense deflection of said lid caused by fluid flowing from said pressure chamber through said ~langed seal into said package; (3) means to move said pressure chamber assembly into and out of sealing position; and (4) means to supply test ~ : 3 B
... ~ .. .
, .
fluid to said pressure chamber.
The inven~ion also provides a pressure~chamber assembly apparatus for use in detectlng lateral leaks in defective seals of packages oi the type wherein flange seals are formed by at least one lateral bond between (1) a flexible lid part of said package and (2) an outwardly-flared flange of a container part of said package, which package is supported on means to hold said package by bearing against the bottom of said flange and means to co-operate with said apparatus to provide a sealing surface and complete a pressure chamber about the outer edge of a said flange seal; said pressure chamber assembly comprising: (a~ a housing over said lid; (b) a first interior gasket means depending from said housing to bear selectively and seal against the top of said flanged seal; ~c) a second exterlor gasket means spaced outwardly from said first gasket means depending from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface; (d) both said gasket means, the exterior edge of said package seal, adapted to define with a said sealing surface a pressure chamber within which said outer edge of said flange is isolated from ambien~ pressure; (e~
said first gasket means enclosing, and seallng from sald pressure chamber, a deflection test zone within said housing and above the non-flanged portion of sald lid; and (f) sensing means in said zone to sense deflection of said lld caused by fluld flowing from said pressure chamber through said flanged seal lnto sald package.
From another aspect, the invention provides a process for testing leaks:ln the flanged seal of a container wherein sald 1~9939~
6041~ 55 flange is foLmed of a flexible lid portion sealed to a hody portion, said process comprising the steps of: (a) isolating ~he exterior edge of said con~ainer seal in a pressure chamber formed of at least two seal means; (b) applying mechanical sealing pressure directly on said flange as part of said isolating step with a first mechanical seal meang; (c) modifying said sealing pressure of said first mechanical seal means on said flange in direc~ response to ~he pressure in said pressure chamber; (d) malntaining a substantially constant pres~ure on a second mechanical seal means; and ~e) measuring deflection o~ said lid portion as a criterion of a leak in said flanged seal.
An advantageous feature of the invention is that a gasketed seal means bearing against the sealed flange portion of the paakage, i.e., the portion of the package under test, is biased such that only a llght sealing pressure is initially applied to said flanged portion of the package to be tested. When test pressure is applied, the light sealing pressure is automaticaIly increased, e.g., by the action of the gas pressure on the sea} means bearing against the seal under test. This action malntains~the differen~tial pressure across the package seal at a sultably low level thereby avoiding both damage to the paakage seal and the sealing off;o~ leaks to be detected.
It has been found that a gasket of thls~mechanical seal means is preferably neither too soft nor too hard for optimum performanae. Shore A~durometer values o~ about 20 to 100 are preferred. This allows the~apparatus to be used with a wide varlety of p`a~ckage~s and seals without incurring any problems ~ ; 4a ~93gfl~
6~412-1655 associated with both excessive deformation of the gasket when pressure is applied and excessive rigidity of the gasket. ~ither factor, when combined with imperfec~ions in ~he quallty o~ web~
used to form the package, can result in excessively-high localized pressure on the flange and damage the seal to be tested.
: : 4b ~, i .......... :
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~9~39~
K68 002(A) The apparatus of the invent ion can be constructed in any number of configurations. A preferred con-figuration is one wherein the pressure chamber assembly surrounds a package and seals off the periphery of a flange-shaped package seal which itself surrounds the periphery of a package. In such circumstances, it is particularly desirable to have initial light-sealing pressure, (e.g. a few ounces of pressure per lineal inch of seal) exerted by the pressure chamber assembly, to be applied by a thin, resilient, sheet forming biasing means and arranged in generally annular rela-tionship with respect to the pressure chamber, and extending cantilevered (as viewed in section) outwardly from a portion of the structure, or housing, of said pressure chamber such that the sheet is forced toward the package seal by test pressure. The seal means which is to bear against the package seal is thus pushed tighter by increased pressure on the resilient sheet. The mechanical seal is thereby automatically ad~usted for air pressure which may invade the package seal under test while, at the same time, maintaining its effective sealing of the pressure chamber assembly against the package.
In the~preferred mode~of the invention, a proxi-mity sensor is centrally carried on the seal assemblyand acts to determine the position of the pressure-flexed lid of the container.
The apparatus is typically operated at a sen-sitivity such that a O.OOS to 0.010-inch movement of thF package lld~causes deflection.
The sensor~illustrated below is a linear proximity sensor available from Electro Corporation of Sarasota, Florida. It is of the type that generates a field below the sensor. When a metal object enters the : ~ :
, 9939~
K6g-002(A) field, such as a flexible aluminum lid construction, eddy currents are induced and these currents are detected by the sensor. The strength of the sensed signal is a measure of how close the metal-bearing lid is to the sensor. Other sensor means can be used which can sense the initial position of a lid and the posi-tion assumed during leak testing. Among such proximity sensors are ultrasonic position-detecting sensors, e.g., of the general type available from Polaroid Corporation of Cambridge, Massachusetts. Ultrasound detecting sensors of the type which can listen to a leak may be used as a detecting means, also. Such sen-sors are sold by American Gas & Chemical Co., Ltd. of Northvale New Jersey. It has been noted that Ultrasound detectors can be used in conjunction with the leak detectors of the invention to listen for air leaking through the lid and thereby extending the func-tion and use of the leak detectors of the invention which, in the form described herein, assume the integrity of the container and lid structure.
ILLUSTRATIVE EMBODIMENT OF THE INVENTION
In this application there is des~ribed a preferred embodiment of the invention and suggested various alternatives and modifications thereof, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can be made within the scope of the invention. The suggestions herein are selected and included for the purposes of illustration in order that others skilled in the art will more fully understand the invention and the prin-ciples thereof and will be able to modify it and embody it in a variety of forms, each as may be best suited to th~ condition of a par-icular case.
~2~9~4 K68-002(A) IN THE DRAWINGS
Figure 1 is a plan view of a lea~-detecting apparatus showing the relationship of a pressure chamber assembly to a container being tested of the invention taken along the Section 1:1 of Figure 2.
Note, however, with respect to Section 1:1, none of the structure of container appears in Figure 1.
Figure 2 is a section in elevation of a leak~
detecting apparatus of the invention showing the rela-tive position of a package being tested to a testingsensor and seal means.
Figure 3 is a schematic diagram indicating the use o~ a proximity sensor in the process of the invention.
Figure 4 is a section showing the construction of a reinforced gasket seal useful with the invention.
Figure ~ is a schematic diagram showing a calibra-tion scheme useful with the invention.
Figure 6 is an alternative dual-force seal embodi-ment of the invention.
It will be understood that the apparatus of the invention will include suitable support means for posi-tioning the container to be tested with respect to the leak-detecting means. Moreover, the air is admitted and allowed out of the system through valves and with the use of electronic controls which are commonly used in the engineering arts. These aspects of the appara-tus are not novel in themselves and are not described in detail herein. Many different versions of such control systems can be used, and they can be readily ~Z~939~
K68-002(A) selected and utilized by engineers familiar wi~h the design of pneumatically and/or electronically actuated automatic test apparatus. Normally guch apparatus wilL
be packaged in an appropriate exterior housing with whatever pneumatic and electronic controls desirable for its operation.
Referring to Figures 1 and 2, it is seen that a leak-detecting apparatus 10 comprises support means 12 for a container 14 such that container 14 is positioned directly under proximity sensor 16 centered in pressure chamber assembly 18 which is positioned to seal the flange 20 of container 14 against support means 12.
The sealing assembly will be positioned by conventional pneumatic or hydraulic prime mover which is not illustrated since such systems are well known and easily implemented by those skilled in the art. When such seal is accomplished, a pressure chamber 23 will form an annular zone around the package, but the pressure from pressure chamber 23 on the package will be limited to that exerted on the external edge of the flanged seal 20 formed by an aluminum foil lid 17 and container body 19.
Pressure chamber assembly 18 comprises an outer sealing block portion 22 as a housing and frame for the components thereof. A sealing gasket 24 is carried within block 22 and adapted to seal block 22 against container-support means 12 with whatever pressure is exerted on the seal by the prime mover. Assembly 18 further comprises an inner seal means comprising a gasket;support 25 and a sealing gasket 27 of a cast two-component polyurethane having a Shore A durometer of about~80. The gasket 27 is, in turn, mounted on gasXet support 25 which~is attached to the outer sealing block 22 by a thin, e.g., about 0.008-inch .
: . .
.
. .
' ' ' " ' ' ' ~Z~3g~
K68-002(A) thick, annular piece of beryllium copper metal. This thin metal section is a spring means 32 as will be further described below. Screws 34 hold annular sprin~
32 to the outer sealing block 22.
Inward from inner sealing block 22 is a sensor-support ring 36 fastened to the inner wall 38 of sealing block 22. Ring 36 is sealed about and holds the centrally-positioned proximity sensor 16 and also comprises spaced conduits 52 which assure that the volume 54 a~ove container 14 will be at ambient pressure maintained outside the pressure chamber. In most circumstances, atmospheric pressure will be con-venient.
Referring to Figure 2, it will be seen that an enclosed volume, in reality pressure chamber 23, is formed by sealing of the seal assembly 18 against con-tainer 14 and container support 12. Test air, typi-cally at 20 to 80 pounds per square inch pressure above atmosphere, is admitted into chamber 23 through value 'V' in conduit 60, as will be described below.
When the fluid is admitted, the pressure will tend to force its way through defects in the container seal 70 which is formed between aluminum lid member 17 and plastic container body 19. This may be an adhesive bonded-seal or a heat seal, or another seal which is intended to be substantially air tight. This test pressure bears against annular spring 32 and helps to maintain the sealing pressure of the inner sealing block 30 against flange 20 of the container even as pressure may build up in the seal itself. Sufficient compensating pressure will ~ind its way into any seal defects and, thus, such defects will not be sealed off by the inner seal.
g3~4 --lo--K68-002(A) When a container is properly positioned, as seen in Figure 2, and test pressure is applied to the edge of seal, air will be forced through defects in the seal and into container 14, forcing the lid upwardly, increasing the output signal of proximity detector 16.
In operation of the apparatus, container 14 is brought into test position on support 12. Thereupon the sealing ass-embly 18 is caused to descend into sealing position as shown in Figure 2. At this point the interior seal block 25 and its gasket 27 rest only lightly on the sealed flange portion 20 of the con-tainer. Test fiuid, usually a gas liXe air or nitrogen or helium, is used to bring chamber 23 up to test pressure. Once pressure is reached, the output of the proximity detector 16 is taken as indicative of the initial vertical position of lid 17. It is suggested that this initial reading be delayed for a very short time, e.g., 0.05 to 0.3 seconds, in order to allow the package to adapt its initial test geometry to the pressure. The actual test time will depend on the nature of a particular package. It can be less than one second (but will commonly be about 2 to 3 seconds and usually be from 1 to 6Q seconds). Continuous reading of the sensor output will be obtained as a measure of the vertical position of the lid, i.e., the position assumed as a result of any gas f]ow through seal defects into the container.
The height of the lid will be used in determining whether the seal is defective. It is convenient to have a "reject signal", e.g., a red light or buzzer or both activated on sensing of a rejected package.
' , ~9939~
K68-002(A) In any event, the pressure chamber is depressurized, the sealing assembly is raised and the package is removed for another cycle.
Other modes of operation can also be used. For example, time could be utilized as a constant test period and the failure of the sensor output to indicate an unde-sirable upward movement of the device during th~ set time would then indicate a suitable seal.
Figure 3 illustrates schematically the sensory control of a seal integrity tester constructed according to the invention. Conventional pneumatic and electrical apparatus such as solenoid valves and pneumatic conduits are not shown in an detail because these will be understood by those skilled in the art on reading the description.
With a package 14 to be tested in position, a test button is used to initiate a test cycle. A timer 303 is set to a maximum test time. Simultaneously, a reset signal is sent to bi-stable f~lip-flop 305 via conduit 306. ~ visual indication of a suitable state of the flip-flop is sent to green light 307 via electrical con-duits 308 and 310. AIso, valve 309 is actuated via con-duits 308 and 312 to bring the sealing assembly (18 as seen in Figures 1 and 2) down to form the pressure chamber 23 around the seal to be tested.
Then, valve 313 is opened to allow gas to enter the sealing assembly. The timer is started. Then, after a 0.1 second delay 316, (in which time the mechanical shifts in package configuration due to the stresses of the pressure and sealing action may occur) the test time will be started via conduit 318. When the 0.1 second delav ~nds, ~ample-and-hold ~r-uit 317 will go to the i lZS~3~
K68--002 (A ) hold state via conduit 322. The signal to b~ held at this ti~e is a signal from sensor 16 which is indicative of the vertical position of a metal package lid. This signal level on conduit 319 from sensor 16 will be held on conduit 324 even though the line 319 signal continues to vary. The signal on conduit 322 also enables the read gate 321. Read gate 321 is used to avoid setting the flip-flop at times during chamber closure, pressuriza-tion, and other times when testing is not taking place.
If the seal under test has no leaks, the signal level on conduit 319 will remain the same as the signal level on line 324. Thus, the output signal from com-parator 323 on conduit 326 will not change and therefore will not allow a "set" command signal via conduit 329.
The logic level signal on conduit 308 will not change, and the green "OK" lamp 307 will remain on.
The timer 303 will time down to zero and terminate the test by a signal sent through conduit 331 to the sequence controls. Alternately the test can be ter-minated by a stop button 328. In ~either case both air valves 309 and 313 simultaneously operate to depressurize and open to lift the sealing assembly.
As indicated above, if the seal being tested has a leak, the distance between the lid puffed up by gas leaking into the package and the sensor will become smaller. In such a case, the signal levels on conduit 319 and conduit 324 will be different because the con-duit 319 signal voltage will increase as the lid con-tinues to rise. Comparator 323 will send a signal based on this difference through conduit 326, thereby enabling read gate 321 and causing a "set" logic com-mand to be output by bi-stable flip-flop 305. The ~e~ult~nt signal on conduit 3~8 will put out the green ' : "' ' ' . : ' ~LZ~3g4 K68-002(A) light 307 and put on the red light 3~0. The timer will normally stop at this time. The pressure chamber will be depressurized and raised.
It is important that gasket 27 be radially stable with respect to the apparatus and package. Therefore it is often advisable to reinforce the gasket with an internal support structure 40 as seen in Figure 4 wherein a polyurethane gasket 27 of Shore A durometer of about 80. The annular spring 32 is fixed to the aluminum support structure 40 and positioned against a small overlap in structure 40 at 44. V-grooves 46 are used to help hold the gasket 27 in position.
The apparatus described herein is already constructed to have a leak-sensitivity of about 0.2 cubic centimeter per second leak rate.
In addition to the features of the invention described above, it is sometimes advisable to provide a calibrating means with the apparatus as seen in Figure 5. One such calibration means can comprise a hypoder-mic needle-like conduit 502 adapted for insertion into the headspace 504 of a container 514. A small calibrated leak device 516 (of the type commerically available) controls the amount of simulated leak gas being passed into the package.
Figure 6 illustrates schèmatically another sealing assembly apparatus according to the invention. A
spring 602 is utili~ed to limit initial pressure on flange 20. However, as pressure increases in pressure zone 623, it tends to force the gasket 627 downwardly as a result of further pressure exerted on the spring by spring cap 604. The sealing pressure on gasket 627 however is independent from the mechanical sealing ~2~3~
-~4-K68-002(A) pressure exerted by the prime mover on gasket 24 via the principle annular sealing block 622. o-rings 630 and 632 provide gas seal means between the pressure zone 623 and ambient and the spring chamber 635. The rings also provide sufficient flexibility and movement to allow the differential pressure to be effective at gaskets 627 and 24.
It is further noted that the apparatus can be used in a suction mode with the "pressure chamber" having a pressure below the ambient pressure. In such a case, the deflection of the lid, indicative of a leak, would be downward.
Moreover, in the suction mode, it is possible to utilize chemical sensors to detect minute quantities of materials in the container which are sucked out and use these quantities as a criterion of leak severity.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which might be said to fall therebetween.
Claims (17)
1) Leak detecting apparatus for use in detecting lateral leaks in defective seals of packages of the type wherein flange seals are formed by at least one lateral bond between (a) a flexible lid part of said package and (b) an outwardly-flared flange of a container part of said package, said apparatus having;
(1) support means to hold said package by bearing against the bottom of said flange and to provide a sealing surface;
(2) a pressure chamber assembly adapted to form a pressure chamber about the outer edge of a said flange seal, said pressure chamber assembly comprising;
(a) a housing over said lid;
(b) a first interior gasket means depending from said housing to bear selectively against the top of said flanged seal as it rests on said sealing surface of said support means;
(c) a second exterior gasket means spaced outwardly from said first gasket means depending from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface;
(d) both said gasket means, the exterior edge of said package seal, and said sealing surface defining a pressure chamber isolating said outer edge of said flange from ambient pressure;
(e) said first gasket means enclosing, and sealing from said pressure chamber, a deflection-test zone within said housing and above the non-flanged portion of said lid; and (f) sensing means in said zone to sense deflection of said lid caused by fluid flowing from said pressure chamber through said flanged seal into said package;
(3) means to move said pressure chamber assembly into and out of sealing position; and (4) means to supply test fluid to said pressure chamber.
K68-002(A)
(1) support means to hold said package by bearing against the bottom of said flange and to provide a sealing surface;
(2) a pressure chamber assembly adapted to form a pressure chamber about the outer edge of a said flange seal, said pressure chamber assembly comprising;
(a) a housing over said lid;
(b) a first interior gasket means depending from said housing to bear selectively against the top of said flanged seal as it rests on said sealing surface of said support means;
(c) a second exterior gasket means spaced outwardly from said first gasket means depending from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface;
(d) both said gasket means, the exterior edge of said package seal, and said sealing surface defining a pressure chamber isolating said outer edge of said flange from ambient pressure;
(e) said first gasket means enclosing, and sealing from said pressure chamber, a deflection-test zone within said housing and above the non-flanged portion of said lid; and (f) sensing means in said zone to sense deflection of said lid caused by fluid flowing from said pressure chamber through said flanged seal into said package;
(3) means to move said pressure chamber assembly into and out of sealing position; and (4) means to supply test fluid to said pressure chamber.
K68-002(A)
2. Apparatus as defined in Claim 1 wherein said first gasket means is mounted on biasing means to limit sealing pressure on said flanged seal.
3. Apparatus as defined in Claim 2 wherein said first gasket means is formed of a resilient material having a Shore A durometer of from about 20 to about 100 .
4. Apparatus as defined in Claim 2 wherein said biasing means is a thin resilient sheet extending out-wardly from said pressure chamber assembly, said sheet forming a portion of the wall of said pressure chamber and wherein said wall, when pressurized, forms means to approximately balance any gas pressure within a said defective seal.
5. Apparatus as defined in Claims 2, 3 or 4 wherein said pressure-chamber assembly seals against said flanged portion around the entire periphery of said package.
6. Apparatus as defined in Claim 4 wherein said biasing means extends outwardly to bias said first gasket means around the entire periphery of said package.
7. Apparatus as defined in Claim 2 wherein said pressure-chamber assembly is generally ring-shaped and carries of proximity-sensor at its central portion forming means to detect said vertical position of said lid.
K68-002(A)
K68-002(A)
8) Apparatus as defined in Claim 2 wherein said biasing means is a thin pressure-deflectable sheet carried on said housing of said pressure chamber assembly and extending outwardly and horizontally over said test zone to form a wall defining part of said pressure chamber, said wall carrying said first gasket means thereon and said wall being responsive to pressure in said pressure chamber to determine test sealing pressure applied against said flanged seal by said first gasket means.
9. A process for testing leaks in the flanged seal of a container wherein said flange is formed of a flexible lid portion sealed to a body portion, said process comprising the steps of;
(a) isolating the exterior edge of said container seal in a pressure chamber formed of at least two seal means;
(b) applying mechanical sealing pressure directly on said flange as part of said isolating step with a first mechanical seal means;
(c) modifying said sealing pressure of said first mechanical seal means on said flange in direct response to the pressure in said pressure chamber;
(d) maintaining a substantially constant pressure on a second mechanical seal means; and (e) measuring deflection of said lid portion as a criterion of a leak in said flanged seal.
K68-002(A)
(a) isolating the exterior edge of said container seal in a pressure chamber formed of at least two seal means;
(b) applying mechanical sealing pressure directly on said flange as part of said isolating step with a first mechanical seal means;
(c) modifying said sealing pressure of said first mechanical seal means on said flange in direct response to the pressure in said pressure chamber;
(d) maintaining a substantially constant pressure on a second mechanical seal means; and (e) measuring deflection of said lid portion as a criterion of a leak in said flanged seal.
K68-002(A)
10) A pressure-chamber assembly apparatus for use in detecting lateral leaks in defective seals of packa-ges of the type wherein flange seals are formed by at least one lateral bond between (1) a flexible lid part of said package and (2) an outwardly-flared flange of a container part of said package, which package is sup-ported on means to hold said package by bearing against the bottom of said flange and means to co-operate with said apparatus to provide a sealing surface and complete a pressure chamber about the outer edge of a said flange seal: said pressure chamber assembly comprising;
(a) a housing over said lid;
(b) a first interior gasket means depending from said housing to bear selectively and seal against the top of said flanged seal, (c) a second exterior gasket means spaced out-wardly from said first gasket means depending from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface;
(d) both said basket means, the exterior edge of said package seal, adapted to define with a said sealing surface a pressure chamber within which said outer edge of said flange if isolated from ambient pressure;
(e) said first gasket means enclosing, and sealing from said pressure chamber, a deflection-test zone within said housing and above the non-flanged portion of said lid; and (f) sensing means in said zone to sense deflec-tion of said lid caused by fluid flowing from said pressure chamber through said flanged seal into said package.
K68-002(A)
(a) a housing over said lid;
(b) a first interior gasket means depending from said housing to bear selectively and seal against the top of said flanged seal, (c) a second exterior gasket means spaced out-wardly from said first gasket means depending from said housing, surrounding and spaced from said interior gasket means and forming means to seal against said sealing surface;
(d) both said basket means, the exterior edge of said package seal, adapted to define with a said sealing surface a pressure chamber within which said outer edge of said flange if isolated from ambient pressure;
(e) said first gasket means enclosing, and sealing from said pressure chamber, a deflection-test zone within said housing and above the non-flanged portion of said lid; and (f) sensing means in said zone to sense deflec-tion of said lid caused by fluid flowing from said pressure chamber through said flanged seal into said package.
K68-002(A)
11. Apparatus as defined in Claim 10 wherein said first gasket means is mounted on biasing means to limit sealing pressure on said flanged seal.
12) Apparatus as defined in Claim 11 wherein said biasing means is a thin pressure-deflectable sheet carried on said housing of said pressure chamber assembly and extending outwardly and horizontally over said test zone to form a wall defining part of said pressure chamber, said wall carrying said first gasket means thereon and said wall being responsive to pressure in said pressure chamber to determine test sealing pressure applied against said flanged seal by said first gasket means.
13. Apparatus as defined in Claim 11 wherein said first gasket means is formed of a resilient material having a Shore A durometer of from about 20 to about 100 .
14. Apparatus as defined in Claim 11 wherein said biasing means is a thin resilient sheet extending out-wardly from said pressure chamber assembly, said sheet forming a portion of the wall of said pressure change and wherein said wall, when pressurized, forms means to approximately balance any gas pressure within a said defective seal.
15. Apparatus as defined in Claims 11, 13 or 14 wherein said pressure-chamber assembly seals against said flanged portion around the entire periphery of said package.
16. Apparatus as defined in Claim 14 wherein said biasing means extends outwardly to bias said first gasket means around the entire periphery of said package.
K68-002(A)
K68-002(A)
17. A pressure-chamber assembly as defined in Claim 11 wherein said assembly is generally ring-shaped and carries of proximity-sensor at its central portion forming means to detect said vertical position of said lid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87907786A | 1986-06-26 | 1986-06-26 | |
| US879,077 | 1986-06-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1299394C true CA1299394C (en) | 1992-04-28 |
Family
ID=25373395
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000540516A Expired - Lifetime CA1299394C (en) | 1986-06-26 | 1987-06-25 | Testing containing seals |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS6342439A (en) |
| CA (1) | CA1299394C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0339626A (en) * | 1989-07-05 | 1991-02-20 | Cosmo Keiki:Kk | Leak inspecting method for sheet type seal and leak inspecting device using said method |
| DE4017693C2 (en) * | 1990-06-01 | 1995-11-16 | Martin Lehmann | Leakage test |
| JP4763425B2 (en) * | 2005-11-08 | 2011-08-31 | デルタ工業株式会社 | Slide adjuster for vehicle |
-
1987
- 1987-06-25 JP JP15876587A patent/JPS6342439A/en active Pending
- 1987-06-25 CA CA000540516A patent/CA1299394C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6342439A (en) | 1988-02-23 |
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| MKEX | Expiry |