IE61334B1

IE61334B1 - Apparatus for controlling sealing in a container for holding a fluid under pressure

Info

Publication number: IE61334B1
Application number: IE303088A
Authority: IE
Inventors: Maurice Riviere; Daniel Dauteuil
Original assignee: Metal Box Plc
Priority date: 1987-10-07
Filing date: 1988-10-06
Publication date: 1994-11-02
Also published as: GR3004574T3; DK559188D0; PT88680A; EP0311475A1; PT88680B; FR2621689A1; EP0311475B1; IE883030L; FR2621689B1; ES2031618T3; DE3870566D1; DK559188A

Abstract

The sealing-monitoring device is used for a vessel (1) with a bottom (11) attached to a tubular body (10) by means of a rolled crimping bead (13). It comprises a head (4) for sealing connection to a compressed-gas source (49), a base (2) with a cylindrical side wall (20), into which an O-ring (22) fits, and a plane bottom wall (21) into which a circular gasket (23) fits. The vessel body (10) bears on the O-ring (22) and the bead (13) on the gasket (23) by means of the metal sheet where the bottom (11) is formed. Delimited in this way is an enclosure (25) in communication with a pressure-gauge capsule (3). If there is a leak, the gas increases the pressure in the enclosure (25) which is of very small dead volume. If the pressure increase exceeds a threshold, a fault signal appears at (55).

Description

This invention relates to a device for checking for leaks in a container intended for holding a fluid under pressure, and comprising a tubular body and a bottom joined along a circular ridge in a plane perpendicular to the axis of the body, the device including means for making a temporary leak-proof connection of the container to a source of pressurized gas, an enclosure into which the container penetrates in leak-proof fashion, and which is equipped with means for measuring pressure, and associated means, coupled to the pressure-measuring means, for revealing the increase of pressure in the enclosure which results from an accidental leak of pressurized gas across the ridge during a determinate interval.

The containers whose leaktightness is to be checked according to the present invention are essentially aerosol containers, the bottom of which, being concave in order to withstand the pressure without compromising the vertical stability of the container, is joined by making a rolled seam from the edges of the bottom and of the body, with several folds. The leak-proofing is perfected by the application of a dressing of rubber along the seam ridge, applied in the soft state.

These aerosol containers (atomizers) comprise inter alia a dome at the end of the body opposite the bottom, and generally applied likewise by making a seam, and they present an edged central opening where an atomizer valve is fixed at a later stage of manufacture.

Since we are concerned with articles manufactured by mass production, the procedure for checking leaktightness should be quick to apply and should lend itself to automation .

The basic procedure consists of introducing the container into a fluid-tight enclosure, following which the opening in the dome of the container receives a sealing spout connection to a source of pressure, with a leak-proof joint. The enclosure is connected to a manometer. A gas pressure of several bar is applied to the interior of the container, and the pressure which obtains within the enclosure, on the outside of the container, is measured after a predetermined period during which the pressure is applied. If this pressure is significantly raised above the starting pressure, the reason is that gas has passed from the inside of the container to the outside across a leak in the container wall.

French patent specification FR-A-2 515 348 describes a device of this type. However, instead of directly monitoring a rise in pressure in the test enclosure, the gas within that enclosure is aspirated at a constant rate, and the time necessary for obtaining a given depression is determined. This interval is significantly increased in the case of a leak.

Although this document gives no indication of the minimum detectable rate of leaking, and the corresponding measurement interval, it does not seem that the indicated differences of design would be capable of reducing the measurement interval corresponding to the minimum leakage, - 4 since these differences do not apply to the parameters, described further down herein, which directly affect the duration.

In practice leaks occur at the seams. Moreover, especially if the pressure on the interior of the container is relatively high in order to apply significant force to the seams, it is found that very slow leaks are very rare.

Thus, those containers that show a rate of leakage not 3 - 5 exceeding 0.5 cm /min (1.1 x 10 g/s in standard units) under 9 bar of pressure differential, have a leak-tightness which is sufficient in practice for their intended application.

The present devices, acting according to the method described above, react in about fifteen seconds to the 3 minimum rate of leakage, 0.5 cm /min.

It will be easily understood that checking for leaks on mass-production lines must be done on an automatic machine having a barrel with many positions where the containers are arrested on a feed conveyor, charged in one position, connected to the supply connector, enclosed in the enclosure and pressurized for a predetermined interval, then undergo a pressure measurement in the enclosure, are restored to atmospheric pressure internally, removed from the enclosure and finally, according to the test results, discharged to an onward conveyor if they are good, or discarded if they leak.

Because of the great number of the operations, and of the time interval necessary for pressurizing the containers, a high rate of production demands a machine with a large number of positions, which is both expensive and bulky.

Thus a typical test machine (Borden model AP-36-600) includes a barrel with 36 positions and occupies a space about 3 m x 1.3 m x 2.7 m.

It is immediately clear that a substantial reduction of the response time, ie the pressurization period at the end of which a significant increase is noted in the enclosure in response to the typical minimum leakage (0.5 cm /min) would be able to reduce noticeably the cost and the bulk of a test machine, for equal performances.

There is little that can be done to improve the sensitivity of the manometer, which should give a reliable discrimination between the pressure increase resulting from a leak and the accidental feed variations of the pressure resulting from temperature variations and machine manoeuvres (rapid closing of the enclosure in particular).

Increasing the pressure inside the containers will have little efficacy, because one may not exceed the values which the containers can withstand without risking permanent deformation and deterioration. Moreover the leakage rate is practically proportional to the pressure difference between the two ends of the leakage channel. If we double the pressure in the container (18 bar instead of 9), the leak rate will be doubled, which will divide the response time by two, ie a limited gain in sensitivity against an excessive increase in pressure.

The third parameter on which one might act is the volume of the enclosure, since the speed with which the pressure rises in response to a given leak is inversely proportional to that volume of the enclosure which remains after introduction of the container, ie the dead volume.

In practice the reduction of dead volume takes place by reduction of the diameter of the enclosure. The use of this expedient is limited by the necessity of leaving a certain play between the body of the container and the lateral wall of the enclosure, both for avoiding damage to containers with bad axial orientation and because of the piston effect of the body introduced into the enclosure at high speed. Finally the volume defined by the concave bottom and the volume to the height of the dome represent incompressible dead volumes.

Statistical analyses of sealing defects in containers for pressurized fluid, especially aerosol dispensing cans, carried out by the applicant have shown that more than 80% of the defects recorded were in the seams, especially the seam of the bottom to the body. It appeared as a result that checking this seam for leaks would constitute an effective check on the fluid-tightness of the container.

Thus, in order to produce less costly and bulky test machines than the conventional machines, with at least equal performances, especially outputs, the invention proposes a device for checking for leaks in a container intended for holding a fluid under pressure and having a tubular body and a bottom joined to the body along a circular ridge in a plane perpendicular to the axis of the body, the device including means for making a temporary leaktight connection of the container to a source of pressurized gas, an enclosure into which the container is introduced in leaktight fashion, the enclosure being equipped with pressure-measuring means, and associated means coupled to the pressure-measuring means, capable of revealing the pressure increase in the enclosure resulting from an accidental gas leak under pressure across the container in a given period, characterized in that » in testings the enclosure is delimited on the one hand by a seating having a cylindrical side wall and a plane base wall which is perpendicular to the side wall, and two annular seals of elastomer fitted in parallel respectively into the side wall and the base wall, and on the other hand by the body and the bottom of the container which abut against one or the other of the annular seals respectively, with the ridge being disposed adjacent and between the annular seals and between them. - 7 It will be understood that in this way the enclosure presents a minimal dead volume, so that the minimal leak can be identified in two seconds from opening the pressurizing valve.

Moreover, the placement of the container on the seating requires only a short translatory movement, which is rapid compared with the translation necessary on the conventional machines (greater than the length of the body).

For preference, for a container in which the bottom and the body are joined by a rolled seam of several folds, the first fold, which defines the resting base of the container, bears on the seal fitted in the base wall.

According to whether the sealing is performed by outward or inward rolling, the cylindrical wall of the seating is disposed externally or internally of the seam ridge, and the seal fitted in this cylindrical wall bears upon the body or against the bottom.

Other features and the advantages of the invention will appear, furthermore, from the following description given by way of example, with reference to the attached drawings in which: Figure 1 is a section in elevation of a device according to the invention, with an associated block diagram; Figure 2 is a section of the seating of the device of figure 1, intended for a container with a seam rolled outwardly; Figure 3 is a section through a variant of the seating, intended for a container with a seam rolled inwardly; Figure 4A is a section of a head for connecting the container to a pressure source, in the position of use; Figure 4B is a section of the head shown in Figure 4A, in the inserted position; Figure 5 is a section through a variant of the head for checking the seam of the dome for leaks.

According to the embodiment chosen and represented in figure 1, the device is intended for checking for leaks in a container 1 intended when complete to contain a fluid under pressure, such as an aerosol atomizer can, and consisting of a tubular body 10, a concave bottom 11 joined to the body 10 by a rolled seam forming a ridge 13 of several folds, and of a dome 12 likewise joined on by a rolled seam 14, and having a central opening bounded by a rolled lip 15. The fluid-tightness of the seams 13 and 14 is perfected by application of a rubber seal applied in the soft state, in conventional manner.

The device comprises a seating 2 having a cylindrical side wall 20 and a plane base wall 21, perpendicular to the side wall 20.

A sealing ring 22 of elastomer is fitted into the side wall 20, and similarly a sealing ring 23 of rectangular section, likewise of elastomer, is fitted into the base wall 21. As can be seen in figure 1, and again somewhat better in figure 2, the container 1 is inserted into the interior of the cavity formed by the side wall 20 and base wall 21 of the seating 2, so that the bottom seam ridge 13 bears against the seal 23 fitted in the base wall 21, whereas the body 10, coaxial with the cylindrical wall 20, is enclosed by the sealing ring 22 fitted into that wall.

Since the seam ridge 13 is rolled outwardly, the metal plate which constitutes the bottom 11 is at the outside of the ridge as far as the second fold, and rests on the seal at the locus of formation of the first fold. There is thus formed an annular enclosure 25 defined firstly by the side wall 20 and base wall 21, and secondly by the lower part of the body 10 and the bottom plate 11 between the first and second folds of the seam ridge 13.

It will be noted that, if a leakage channel has formed in the seam ridge 13, it will necessarily open into the annular enclosure 25, since it will follow the direction of the rolling.

The enclosure 25 is placed in communication with a manometer capsule 3 contained therein, by means of a channel 24, consisting, as can be better seen from figure 2, of a succession of mutually perpendicular bores, stopped off by screwed plugs.

This channel 24 opens into the enclosure 25 through the cylindrical wall 20, between the seal 22 which is fitted there, and the junction with the base wall 21. Towards the manometer capsule 3, it opens at the centre of a truncated conical projection 29 of the seating 2.

As can be better seen in figure 2, the manometer capsule 3 comprises a deformable wall consisting of an elastic membrane 30 secured around its edge between the edge 28 of a chamber 31 formed in the seating 2, and a breech 34. The membrane 30 comprises a circular wave which is housed between the edge 28 and the truncated conical central projection 29 formed in the seating 2, so as to reduce the dead volume of the chamber 31 beneath the membrane 30.

At the centre of the membrane 30, on the side thereof facing the breech 34, there is fixed a disc 32 of ferromagnetic material. Along the axis of the capsule 3 and facing the disc 32 there is disposed an induction coil or captor 33, having a feed cable 35.

It will be understood that a leak opening within the enclosure 25 will tend to push the membrane 30 away from contact with the seating 2, so that as the disc 32 approaches the inductive captor 33, the latter emits a signal representing the volume of gas which has passed through the leak.

If figures 4A and 4B are inspected for the details of the connection head 4 which are represented with insufficient clarity in figure 1, it will be seen that the head 4 comprises a socket 40, at the end of a neck 41, this socket 40 serving to cover the dome 12 of the container 1 by a truncated conical recess 40a, having a throat 40b for the centralized housing of the lip 15 of the central opening of the dome.

The head 4 comprises moreover an axial tube 42, sliding within the neck of the socket 41 and connected to a source 49 of compressed air by way of an electrically operated valve 48.

The tube 42 penetrates axially into the container 1, and its end is provided with a stop member 43, held by a hollow screw 43a engaged in the lumen of the tube 42.

This stop member 43 has a planar periphery 43b upwardly turned, and a truncated conical centre portion 43c which extends upwardly to join the exterior of the tube 42.

An elastically deformable tubular seal 44 is inserted around the tube 42 and held between the neck 41 and the stop member 43.

Moreover this seal 44 is held, by reason of enlargement 44a, between the neck 41 and the inside edge of the socket 40.

When placing the head 4 on the dome 12 of the container 1, the tube 42 is lowered (figure 4B) so that the stop member 43 is below the seal 44. This seal 44 can thus be inserted in the central opening of the dome 12. Subsequently the tube 42 is retracted (figure 4A, figure 1) until the truncated conical central portion 43c engages the bottom of the seal 44, and the planar periphery 43b abuts the lower face of said seal 44.

It will be understood that the consequent radial expansion of the seal 44 ensures that it is held in leaktight manner upon the lip 15 which borders the central opening of the dome 12, while the combination of expansion by the central portion 43c and of the pressure of the planar periphery 43b constrains that part of the seal 44 which has penetrated into the central opening of the dome 12 to form a radial cushion which bears against the lip 15, so as to prevent the container 1 from expulsion under the effect of the internal pressure.

The operation of the device is governed by associated means 5 which will be described below.

In order to check the leaktightness of the seam ridge 13 of the container 1, said container is introduced into the seating 2, as was mentioned in the description of this seating; the head 4 is positioned with the tube 42 in the lowered position, until the dome has been covered by the socket 40, and then the tube 42 is retracted as has been said above during the description of the head 4. Afterwards a central relay 50 sends a signal firstly to the valve 48 to cause it to open and thus establish communication between the compressed air source 49 (at about 9 bar) with the interior of the container 1, and secondly to a delay circuit 51, set to about 2 seconds.

As was said during the description of the pressure measuring capsule 3, if a leak exists in the ridge 13, the membrane 30 and its ferromagnetic disc 32 are progressively displaced towards the inductive captor 33 which responds by emitting a progressively intensifying signal. This signal is forwarded to one input of a differential amplifier 52 mounted as a comparator with an adjustable threshold. If the signal emitted by the captor 33 exceeds the threshold value set by the potentiometer 53, the amplifier 52 emits a signal which is applied to a first input of an AND gate 54.

When the end of its period arrives, the delay circuit 51 emits a signal which is applied to the second input of the AND gate 54, as well as to the central relay 50 to finish the test cycle.

Thus, if the leak loss of the ridge 13 has caused a swing of the comparator 52 before the delay circuit 51 has emitted its end-of-period signal, when that signal arrives the two inputs of the AND gate 54 will be in the up state, and a signal will appear at the output 55, signifying that the ridge 13 is leaking.

Conversely, if the comparator 52 has not swung at the time of appearance of the end-of-period signal of the delay circuit 51, the ridge 13 will be taken to be leak-tight.

The variant represented in figure 3 relates to a container 1 in which the bottom 11 is joined to the body 1 by a seam rolled inwardly, so that, in the seam ridge 113, the metal sheet which constitutes the body 10 is located on the outside as far as the second fold.

The seating 102, then, comprises a cylindrical side wall 120, and a planar base wall 121, perpendicular to the side wall 120. But here the side wall 120 is disposed on the inside of the seam ridge 113 and thus of the body 110. An elastomer ring seal 122 is fitted in the upper part of the side wall 120 so as to bear against the bottom 11, while the first fold of the seam ridge 113 bears against an annular seal 123 of rectangular cross-section, likewise of elastomer, and fitted in the base wall 121.

Thus, when the container 1 is placed upon the seating 102, there is defined a sealed enclosure 125 limited on the one hand by the side wall 120 and the base wall 121, and on the other hand by the body 10 and the bottom 11, and the body 10 extends into the seam ridge 113 at the outside of the latter as far as the second fold. As with a ridge rolled towards the outside, an accidental leak channel thus opens within the enclosure 125.

A channel 124 which opens to the enclosure 125 in the cylindrical side wall 120 between the seal which is fitted there and the junction with the base wall 121, establishes communication between the enclosure 125 and a pressuremeasuring capsule 3 identical to the capsule of figure 2.

It follows that, to transform the device for a seam ridge 13 outwardly rolled into a device for a seam ridge 113 inwardly rolled, it is sufficient to replace the seating 2 by the seating 102.

To consider figure 5, the connection head 4 there represented comprises, for its function of connecting the container 1 to a source of pressurized gas, the same elements as does the head which is represented in figures 1 and 4AS 4B, which carry the same reference numerals.

But the socket 40 extends to a skirt 40j, in the direction of the bottom of the container 1, around the rolled seam 14 of the dome 12 above the body 10; a ring seal 62 is fitted within this skirt 40j, so as to come to bear against the body 10 in the neighbourhood of the junction bulge 14. The latter is thus enclosed in the inner space 135 within the socket 40, between the tubular seal 44 and the annular seal - 14 62. This inner space 135, together with the walls of the container 1, constitutes an enclosure comparable to the enclosures 25 and 125 previously described. A pressuremeasuring capsule 63. of the same structure as the capsule 3 already described, communicates with the inner space 135 by a channel 40k„ This capsule 63 comprises a flexible membrane 7 with a ferromagnetic disc 72, on the produced axis of an inductive captor 73. The signal emitted by the inductive captor 73 will be treated like that emitted by the captor 33.

It will be appreciated that in this way the leaktightness of the seam of the dome can be systematically monitored, with the same sensitivity as the leaktightness of the seam of the bottom, and without reducing the latter, since the enclosures 25, 125 and 135 are separate.

It will be understood that the device of the invention not only reduces considerably the duration of the cycle, or active duration, which goes from 15 to about 2 seconds, but also permits significant reduction in the duration of the charging and discharging operations, by reducing the longitudinal displacement of insertion of the container into the enclosure, and for connecting the source of compressed air, and by reducing the mass of the bodies being moved.

The invention, of course, is not limited to the described examples, but encompasses all variants lying within the scope of the claims.

In particular, the associated leaktightness analysis means which have only been described by their function, can assume any form or finish which leads to equivalent results, and can be incorporated in or coupled with means for governing a complete test machine.

Claims

1. Device for checking for leaks in a container intended for holding a fluid under pressure, and having a tubular body and a bottom joined to the body along a circular ridge in a plane perpendicuΊar to the axis of the body, the device including means for making a temporary leaktight connection of the container to a source of pressurized gas, an enclosure into which the container is introduced in leaktight fashion, the enclosure being equipped with pressure-measuring means, and associated means coupled to the pressure-measuring means’, capable of revealing the pressure increase in the enclosure, resulting from an accidental gas leak under pressure across the container in a given period, characterized in that, in besting, the enclosure is delimited on the one hand by a seating having a cylindrical side wall and a planar base wall which is perpendicular to the side wall and two annular seals of elastomer fitted in parallel respectively into the side wall and the base wall, and on the other hand by the body and the bottom of the container which abut against one or the other of the annular seals respectively, with the ridge being disposed adjacent the annular seals and between them,

2. Device according to claim 1, for a container in which the ridge has been obtained by rolled closure of several folds, with a sealing gasket of rubber or the like,, characterized in that the first fold of the closure bears against the seal fitted in the base wall of the seating.

3. Device according to claim 2, for a container of which the sealing ridge is outwardly rolled, characterized in that the cylindrical side wall of the seating is disposed externally of the ridge and in that the annular seal fitted in this wall bears against the body.

4. Device according to claim 2, for a container of which the seam ridge is inwardly rolled, characterized in that the cylindrical wall of the seating is disposed internally of the ridge and in that the annular seal fitted in said wall bears against the bottom.

5. Device according to any one of claims 1 to 4, characterized in that the pressure-measuring means consists of a capsule in the form of a disc with one wall being an elastically deformable membrane, and of a proximity captor sensitive to axial displacement of the centre of the membrane.

6. Device according to claim 5, characterized in that the proximity captor is of the inductive type and is disposed in line with the axis of the capsule, while the membrane bears in its centre a disc of ferromagnetic material.

7. Device according to one of claims 5 and 6, characterized in that the capsule comprises a chamber within the seating, and is connected to the enclosure by a channel formed in the seating and opening at the cylindrical wall between the seal which is fitted there, and the junction with the planar wall.

8. Device according to any one of claims 1 to 7, for a container comprising, at the end of the body opposite the bottom, a dome with a central opening bordered by a lip, characterized in that the connecting means consists of a head with a socket which come to cover the dome, and with an axial tube connected to the source of pressurized gas, said tube being adapted to slide axially within the socket and terminating at its anterior end in an abutment and with an elastically deformable tubular seal attached on the tube between the socket and the abutment, the seal being adapted to penetrate partially into the central opening of the dome, while the retraction of the tube with respect to the socket thus causes a radial expansion of the tubular seal which bears in fluid-tight fashion upon the lip bordering the central opening of the dome,,

9. Device according to claim 8, characterized in that the abutment adapts to the tube adjacent the tubular seal by way of a truncated cone.

10. Device according to any one of claims 8 and 9, wherein the dome is secured on the body by a rolled seam, characterized in that the socket extends in one piece, beyond the seam as a skirt with an annular seal which bears against the body, a pressure-measuring means being in communication with an interior space in the socket between the tubular seal and the annular seal.

11. Device for checking for leaks in a container intended to hold a pressurized fluid and comprising a tubular body, a bottom and a dome joined to the body by a rolled seam and comprising a central opening bordered by a lip, the device comprising means for making a temporary leaktight connection of the container to a source of pressurized gas, an enclosure into which the container is introduced in leaktight fashion, the enclosure being furnished with pressure-measuring means and associated means coupled to the pressure-measuring means and capable of revealing the increase of pressure within the enclosure resulting from an accidental leak of pressurized gas across the container in a determinate interval, characterized in that the connecting means consists of a head with a socket serving to cover the dome, with an axial tube connected to the pressurized source and with an elastically deformable tubular seal fitted around the tube, housed in the socket t t and adapted to penetrate partially within the central opening of the dome and to bear against the lip in fluidtight manner by radial expansion, and in that the socket extended in one piece, below the joint as a skirt where an annular seal is fitted which bears against the body, defines between the tubular seal and the annular seal, together with the container which it overlies an enclosure in communication with the pressure-measuring means.

12. Device according to claim 1 for checking for leaks in a container intended for holding a fluid under pressure., substantially as herein described with reference to or as illustrated.in the accompanying drawings.