GB2098338A

GB2098338A - Method and apparatus for testing the longitudinal seams of packaging containers

Info

Publication number: GB2098338A
Application number: GB8213274A
Authority: GB
Original assignee: Schweizerische Industrie Gesellschaft
Current assignee: Schweizerische Industrie Gesellschaft
Priority date: 1981-05-08
Filing date: 1982-05-07
Publication date: 1982-11-17
Also published as: NL8201894A; GB2098338B; CH650208A5; DE3216575A1

Abstract

A method and apparatus for strength testing the longitudinal seams of packaging containers that comprise a wrapping of a packaging material around the material to be packaged, after the packaging material has been sealed by a longitudinal seam and before an end or ends of the package is closed and sealed. At least one end of the longitudinal seam is subjected to a tensile load by means of a probe 1, 11 and using a test force determined by a spring 6, 16. If the longitudinal seam S is unsatisfactory a support element 2, 12 on the probe 1, 11 penetrates into the seam, and a control arm 5, 15, rigidly connected to the control element, brings about a switching action of an electrical element 9, 19 whereby a circuit can be closed, so as to prevent onward movement of a package found to be defective. <IMAGE>

Description

SPECIFICATION Method and apparatus for testing the longitudinal seams of packaging containers The present invention concerns a method and apparatus for testing the longitudinal seams of packaging containers that comprise a wrapping of a pakaging material around the material to be packaged, after the packaging material has been sealed by a longitudinal seam and before an end or ends of the package is closed and sealed.

In view of the stringent requirements regarding freedom from germs and from health-hazarding foreign substances in ordinary and luxury foods, it is imperative that the package be absolutely tight, since it is only in this way that the producer can guarantee the quality of his goods to the consumer. The packaging material, which is usually plastics film or a metal foil coated with plastics material, are tight. However, the longitudinal seams of the package represent danger zones.

For the purpose of testing the longitudinal seam, it has been proposed in DE-A 24 34 823 to measure the actual value of the distance between the two outer faces of the seam and to compare this with the required value. The seam is graded as defective when the required value is exceeded as well as when it is fallen short of. In this way, the inclusion of a foreign body in the zone of the seam, incorrect power feed during sealing, and an inadequate quantity of sealable material can be detected. No conclusion can be drawn regarding the quality of the sealing seam itself. Thus, for example, a seam occluding a foreign body which in itself would cause the required value to be exceeded, could be graded as a good seam because of the absence of sealable material that would on its own result in a shortfall of the required value. Thus, the quality of the seam is not judged.Furthermore, the differences between the actual and required values are very slight, so that the arrangement must react in an extremely sensitive manner in order to be able to detect the differences at all.

The object of the present invention is therefore, to solve the problem of testing longitudinal seams.

According to the invention, this object is achieved by a method in which a probe element is applied against the longitudinal seam at at least one end portion of the package to load the seam by an outwardly acting test force, the distance travelled by the probe element as a result of the deformation of the longitudinal seam is determined, and in that when a certain distance is exceeded, the longitudinal seam is graded as unsatisfactory.

The invention also consists in apparatus for performing the method and comprising two pivotally mounted three-armed toggle levers arranged respectively one to each side of the path of conveyance of a plurality of the containers, each of these levers having a first arm forming a support with a support element insertable into an open end of a container conveyed along the said path to engage the longitudinal seam from the inside, a second arm forming a deflecting lever with a probe roller, and a third arm forming a control lever for measuring the distance.

The invention is based on the knowledge that the quality of the packaging material, i.e. the presence of satisfactorily sealable material, is determined by tests carried out elsewhere, and that foreign-body inclusions in the sealing seam can also be avoided by taking special steps. If, however, a seam is not satisfactorily sealed, the reason for this lies in incorrect setting of the sealing jaws or of their operating temperature. In both cases, the error effects the entire length of the sealing seam and is not localised. In addition, the packages and therefore also the sealing seams are subjected to mechanical stress during transportation to the final user, so that a mechanical tensile test on the sealing seam provides a certain degree of safety in this instance too.Since, as stated above, the sealing seam is good or bad over its entire length, it suffices if at least one end portion of the seam is tested.

An embodiment of the method and apparatus according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a front view of apparatus for performing the method, and Figure 2 is a side view of the apparatus of Figure 1.

As shown in the drawings, a packaging container V, filled with goods B - for example round biscuits -lies in a holder 36 and is sealed by means of a longitudinal seam S. The end portions E of the container V are folded inwards to a limited extent so that it retains the objects B.

Holder 36 forms part of a conveyor (not further shown) for conveying a plurality of the containers V in succession along a path normal to the plane of Figure 1.

Two three-armed toggle levers 10 and 20 are rotatably mounted in a bearing block 7, 1 7 solid with the machine frame by means of a spindle 8, 18 at the apex of the three arms 1,3,5 and 11, 13, 1 5 respectively. A first arm 1, 11 forms a probe arm and carries a support element 2, 12 having a surface duplicating that of the package V.

A second arm 3, 13 carries a probe roller 4, 14 respectively at its free end, and the third, control arm 5, 1 5 is pulled into an end position by a spring 6 and 1 6 respectively. In this end position, the control arm establishes contact with an electrical element 9, 1 9 respectively, i.e. because of its position in relation to this element 9, 1 9 it alters an electrical value such as a capacitance.

Located above the two probe rollers 4, 14 is a deflecting means 30 which is actuated, by way of a two-armed lever 35 rotatably mounted on a bearing block 31 solid with the machine frame, by an eccentric disc 32 which is mounted at an offcentre point 33 on a carrier 34 solid with the machine frame, said eccentric disc being driven.

When the packaging container V reaches the test point, which can be readily ascertained electro-optically or mechanically, the eccentric disc 32 is actuated and the deflecting beam 30 is raised. The toggle levers 10, 20 are thus turned by the action of the springs 6, 1 6. As a result of this rotation, the respective first arms 1, 11 engage in the end portions E of the packaging container V until the support elements 2, 1 2 lie internally against the packaging container and below the longitudinal seam S. The support elements 2, 12 are pressed against the packaging container V by the force of the springs 6, 1 6. At the same time, the third arms 5, 1 5 approach the electric elements 9, 19.When the longitudinal seam S is well sealed, the control arms 5, 1 5 cannot actuate the electrical elements 9, 1 9, if a switch, for example, is used, or the capacitance, in the case of a proximity switch, is not altered sufficiently to cause a switching action. If, on the other hand, a defective longitudinal seam S is present, the support elements 2, 12 penetrate into the seam, and the electrical elements 9, 1 9, are actuated and the seam S is graded as unsatisfactory.

The apparatus has been described for the case where the method of the invention is used for handling biscuit packets. However, it will be obvious to persons skilled in the art that other containers open at one end, e.g. those used for coffee or the like, can be tested in the same way.

A method and apparatus for testing the longitudinal seams of packaging containers that comprise a wrapping of a packaging material around the material to be packaged, after the packaging material has been sealed by a longitudinal seam and before an end or ends of the package is closed and sealed. At least one end of the longitudinal seam is subjected to a tensile load by means of a probe 1, 11 and using a test force determined by a spring 6, 16. If the longitudinal seam S does not satisfy requirements, a support element 2, 12 on the probe 1, 11 penetrates into the seam, and a control arm 5, 15, rigidly connected to the control element, brings about a switching action of an electrical element 9, 19 whereby a circuit can be closed, so as to prevent onward movement of a package found to be defective. Thus a packaging container can be tested for strength on a mechanical basis, and this permits an immediate conclusion to be drawn regarding the condition of the longitudinal seam.

Claims

1. A method of testing the longitudinal seams of packaging containers that comprise a wrapping of a packaging material around the material to be packaged, after the packaging material has been sealed by a longitudinal seam and before an end or ends of the package is closed and sealed, characterised in that a probe element is applied against the longitudinal seam at at least one end portion of the package to load the seam by an outwardly acting test force, the distance travelled by the probe element as a result of the deformation of the longitudinal seam is determined, and in that when a certain distance is exceeded, the longitudinal seam is graded as unsatisfactory.

2. A method according to Claim 1, wherein the longitudinal seam is arranged at the top of the package, the probe element is arranged on support elements secured on supports introduced laterally into the ends of the package, and the distance is the depth of penetration of at least one support element into the seam.

3. A method according to Claim 2, wherein the test force is generated by a spring acting on the support arms.

4. Apparatus for performing the method of Claim 1, comprising two pivotally mounted threearmed toggle levers arranged respectively one to each side of the path of conveyance of a plurality of the containers, each of these levers having a first arm forming a support with a support element insertable into an open end of a container conveyed along the said path to engage the longitudinal seam from the inside, a second arm forming a deflecting lever with a probe roller, and a third arm forming a control lever for measuring the distance.

5. Apparatus according to Claim 4, comprising a deflecting beam for simultaneously actuating both of the second arms.

6. Apparatus according to Claim 4, comprising a control element in an electric circuit and arranged to be actuated by the third arm for the purpose of measuring the distance.

7. Apparatus according to Claim 6, wherein the third limb is an electrode of a capacitive proximity switch.

8. A method of testing the longitudinal seams of packaging containers, according to Claim 1 and substantially as hereinbefore described.

9. Apparatus for testing the longitudinal seams of packaging containers, substantially as hereinbefore described with reference to the accompanying drawings.