GB2259776A

GB2259776A - Flexible envelope testing method and apparatus

Info

Publication number: GB2259776A
Application number: GB9120254A
Authority: GB
Inventors: Willson Barrett David Grant
Original assignee: Barbara Ann Grant
Current assignee: Barbara Ann Grant
Priority date: 1991-09-23
Filing date: 1991-09-23
Publication date: 1993-03-24
Also published as: GB9120254D0

Abstract

Apparatus (10) for testing a seal of an envelope 39 of flexible material comprises a pressure unit 21, 29 pivotally mounted for movement towards a base member 11 by means, e.g. an air cylinder, applying a constant force for effecting compression of the envelope (39). Pivotal movement of the unit is detected by an encoder 37 included in a circuit which signals when the magnitude of the movement is greater than a reference, such magnitude being indicative of an imperfect seal of the envelope. <IMAGE>

Description

Flexible Envelope Testing Method and Apparatus This invention relates to a method of and apparatus for testing integrity of an envelope of flexible material containing a fluid.

It is known to provide apparatus for testing integrity of seals of packages comprising envelopes of flexible material containing foodstuffs. In one type of apparatus packages are conveyed in a path below a series of vertically freely movable circular pads having brushes thereon which successively engage each package when being conveyed along the path. The arrangement is intended to be such that, if a gas contained in a package leaks through a seal of the package when the package is subjected to downward force of the pads, the pads will move downwardly by gravity or spring pressure further than if the seal did not leak. The downward movement of the pads beyond a predetermined position, therefore, is intended to be indicative of integrity of the seal.

A disadvantage of such known apparatus is that it is unreliable because the pressure applied to each package by the successive pads is not accurately controlled and, in consequence, there is little direct relationship between downward movement of the pads and a reference derived from compressing a package under controlled conditions.

Furthermore, vertical movement of the pads is not related to the nominal or original height of a package, in the direction of the vertical movement, resulting from the volume of gas present. Therefore, the indication given does not compensate for variations of pre-fill of gas; thus the degree of leakage is only a small factor in determining the final height of the pack under pressure.

According to the present invention, there is provided a method of testing of an envelope of flexible material containing a fluid comprising the steps of locating the envelope on a support, applying a predetermined force to a movable component in a direction towards the support so as to compress the envelope and expel some of the fluid, measuring movement of the component and comparing the said movement with a reference so as to determine whether the rate of egress of the fluid is within a predetermined range.

Also according to the present invention there is provided apparatus for testing an envelope of flexible material containing a fluid comprising a support for supporting the envelope, compressing means adapted to move towards the support for applying a predetermined compressive force to the envelope when on the support and signal generating means responsive to movement of the compressing means whereby signals generated by the signal generating means are indicative of a rate of emission of the fluid.

Following is a description, by way of example only and with reference to the accompanying drawing, of one method of carrying the invention into effect.

The drawing is a diagrammatic general arrangement of one embodiment of apparatus in accordance with the present invention.

Referring to the drawing, there is shown a support frame 10 having a rigid horizontal bed plate 11 and two pairs of depending brackets 12, 13 located above the bed plate 11, each pair of brackets 12, 13 having journalled therein a corresponding one of a pair of shafts 14, 15, one shaft 15 of which has secured thereto a pulley 16. The shafts 14, 15 each have secured thereto a corresponding end portion of each of two pairs of elongate rigid links 17, 18, each opposite end portion of the links being pivotally connected to a corresponding one of a pair of shafts 19, 20 of a sub-frame 21.

The sub-frame 21 is of substantially elongate rectangular configuration having a rectilinear portion 22 and two pairs of end webs 23, 24. The rectilinear portion 22 has journalled therein at opposite end portions thereof rollers 25, 26 and each pair of end webs 23, 24 has journalled therein a corresponding one of a pair of rollers 27, 28. The roller 27 is adapted to be rotated on a transverse longitudinal axis thereof relative to the corresponding pair of webs 23 by drive means (not shown).

The rollers 25, 26, 27 and 28 engage with an endless belt 29 which extends around the rollers 25 - 28 such that the rollers 25 - 28 and the belt 29 together comprise a conveyor.

The support frame 10 has located thereon a frictionless air cylinder 30 located above the sub-frame 21, the cylinder 30 having a ram 31 which is pivotally connected to a crossbeam 32 secured to the rectilinear portion 22 of the sub-frame 21.

The support frame 10 also is provided with a depending pair of webs 33 in which is journalled a shaft 34 having secured thereto a pulley 35. The pulley 35 and the pulley 16 of the shaft 14 engage with a drive belt 36 which extends around the pulleys 16, 35 so that, when the shaft 15 rotates relative to the brackets 13, corresponding rotation of the shaft 34 is effected relative to the webs 33. An encoder 37 is provided for measuring rotation of the shaft 34 relative to the webs 33.

In use, a conveyor belt 38 delivering flexible packs 39 from a machine (not shown) is guided over the bed plate 11 in the direction of the arrow 'A' indicated in the drawing.

In operation, power is supplied to the roller 27 such as to drive the belt 29 in a direction of the arrow 'A ' from the rotary axis of the roller 26 to the rotary axis of the roller 25 and the speed is controlled such that the belt 29 moves at substantially the same speed as the belt 38, which also moves in the direction of the arrow 'A', thus reducing friction. The cylinder 30 then is operated with a result that the ram 31 lowers the sub-frame 21 so that the run of the belt 29 between the rollers 25, 26 is moved towards the belt 38 thereby reducing a distance 'B' between the belts 29 and 38. The force applied by the cylinder is constant and is such as to compress each of the packs 39 when engaged by the belt 29, at least some air contained whithin an envelope of flexible material of the packs being expelled through a seam or the seams of the envelope.

The force effected by the cylinder 30 is such as to ensure that some deflation or compression of each of the packs 39 is effected while in contact with the belt 29. In consequence the distance 'B' is reduced in proportion to the amount of deflation or compression and the downward movement of the sub-frame 21 causes the links 18 to move in a clockwise direction of the longitudinal axis of the shaft 15, as viewed in the drawing, with a result that the shaft 15 turns relative to the supporting brackets 13 and the shaft 34, due to the drive belt 36, turns relative to the supporting webs 33. The angular movement of the shaft 34 effects generation of signals by the encoder 37.The signals are received in a comparator (not shown) whereby the angular rotation of the shaft 34 is compared with a reference and, if in excess of a predetermined magnitude, an output signal from the comparator will be generated.

Additional apparatus may be provided responsive to such an output signal which would reject a pack 39 on issuing from contact with the belt 29.

In this manner, of the distance 'B' is effectively monitored as each pack 39 travels in contact with the belt 29, and a leakage rate of air issuing from the pack 39 through a seal thereof is determined and thereby provides a test for seal integrity.

It will be appreciated that the shaft 34 may be provided with gearing providing a ratio of, for example, 20:1 and the encoder 37 may provide output at a rate of 10,000 pulse/rev whereby the encoder 37 would be capable of providing 200,000 pulses for each revolution of the shaft 34.

It will also be appreciated that the air cylinder 30 may be replaced by other means, for example a dead weight or a spring, for providing a constant force.

Furthermore, it will be appreciated that packages may also be conveyed in a circular path between fixed support plates and compression plates which are pivotally mounted, the pivots being coupled to encoders. By this means multiple heads may be compactly configured within available line space hence extending the testing time for each package and/or increasing the possible thoughput rate.

Claims

1. A method of testing an envelope of flexible material containing a fluid comprising the steps of locating the envelope on a support, applying a predetermined force to a movable component in a direction towards the support so as to compress the envelope and express some of the fluid, measuring movement of the component and comparing said movement with a reference so as to determine whether the rate of egress of fluid is within a predetermined range.

2. Apparatus for testing of an envelope of flexible material containing a fluid comprising a support for supporting the envelope, compressing means adapted to move towards the support for applying a predetermined compressive force to the envelope when on the support and signal generating means responsive to movement of the compressing means whereby signals generated by the signal generating means are indicative of rate of emission of the fluid through the seal.

3. Apparatus as claimed in Claim 2 wherein the compressing means comprises a component located for pivotal movement relative to a reference.

4. Apparatus as claimed in Claim 3 wherein the signal generating means is responsive to said pivotal movement.

5. Apparatus as claimed in Claim 4 wherein the signal generating means comprises an encoder.

6. Apparatus as claimed in any one of Claims 2 to 6 wherein the support is adapted to move the envelope.

7. Apparatus as claimed in Claim 6 wherein the support comprises a conveyor.

8. Apparatus as claimed in Claim 7 wherein the compressing means comprises a conveyor.

9. Apparatus as claimed in Claim 8 wherein the compressing means conveyor is suspended from a structure.

10. Apparatus as claimed in Claim 9 wherein the compressing means comprises a plurality of links each pivotally connected to the structure.

11. Apparatus as claimed in any one of Claims 2 to 6 wherein the support is adapted to move in a curved path.

12. A method of testing an envelope of flexible material containing a fluid substantially as hereinbefore described and as illustrated in the accompanying drawings.

13. Apparatus for testing an envelope of flexible material containing a fluid substantially as hereinbefore described and as illustrated in the accompanying drawing.