GB2572979A

GB2572979A - Testing Apparatus and method

Info

Publication number: GB2572979A
Application number: GB1806310.7A
Authority: GB
Inventors: Mark Malone Stephen; John Taylor Benjamin; Robert Severn Nicholas
Original assignee: Proseal UK Ltd
Current assignee: Proseal UK Ltd
Priority date: 2018-04-18
Filing date: 2018-04-18
Publication date: 2019-10-23
Anticipated expiration: 2038-04-18
Also published as: GB2572979B; GB201806310D0

Abstract

A testing apparatus comprises an electrically powered actuator for connection to an article to be tested and a controller. The controller is arranged to drive the actuator and determine the current drawn by the actuator and/or speed of the actuator thereby to determine theforce applied by the actuator during its operation. The actuator may be driven at a substantially constant speed. The apparatus may be arranged for peel strength testing of film lids. An apparatus for peel strength testing may be arranged to compare the force applied to remove a film lid from a container with thresholds and thereby determine if a container is satisfactory.

Description

TESTING APPARATUS AND METHOD

Technical Field of the Invention

The present invention relates to testing apparatus and to a method of its use. Particularly, but not exclusively, the present invention relates to a testing apparatus and method for performing peel strength testing to determine the force required to remove a film lid from a container.

Background to the Invention

Heat sealing machines are employed to apply and seal plastic film lids to plastic food containers. In order to ensure a well-adhered and air-tight seal, a number of parameters must be controlled during the sealing process, including times, temperatures and pressures. Optimum operational parameters may vary between heat sealing machines. Optimum operational parameters may also vary depending on the shape of container or composition of plastic materials.

In addition to providing a seal that preserves the quality of the food contained, the consumer must be able to peel the lid from the container in a satisfactory manner. The consumer experience will be enhanced by a film lid that peels easily and consistently.

At the present time, it is difficult to determine the parameters that provide these desired characteristics. It would be advantageous to provide an apparatus and a method for quantifying the quality of the seal of a plastic film lid by measuring the force required to peel the lid from the container throughout removal of the lid from the container.

It is an object of embodiments of the present invention to address this need.

Summary of the Invention

According to a first aspect of the present invention there is provided a testing apparatus comprising an electrically powered actuator arranged to apply a force to an article to be tested and a controller, wherein the controller is arranged to drive the actuator and determine the current drawn by the actuator and/or the speed of the actuator thereby to determine changes in the force applied by the actuator during its operation.

An electrical actuator may conveniently be used to apply a force to a film lid of a container to remove the lid. The current drawn by an electrical actuator is typically proportional to the force it delivers. So, determining current is a convenient way of measuring force or at least relative force applied by the actuator. As an alternative to knowing or determining the current directly the force provided by an electrical actuator may also be determined by supplying a known power supply to the actuator, such as a constant voltage, and measuring the speed of the actuator.

In one embodiment the controller is arranged to drive the actuator at a substantially constant speed and to determine the current drawn by the actuator. This facilitates determining the force or relative force applied by the actuator during operation. It also allows measurements of different articles to be easily compared.

The apparatus may comprise a connector arranged to connect to the article to be tested, and thus enable the actuator to apply a force to the article. The connector may comprise a clamp or fastener. A clamp may have substantially flat mating surfaces.

The actuator may be arranged to move the connector through a linear, preferably a substantially horizontal, path.

The actuator may be a linear actuator or it may be a rotary actuator such as an electric motor or servomotor connected to a mechanism which converts rotary to linear motion. In one arrangement a rotary actuator drives a belt or chain which runs through a partially linear path. The belt or chain may be endless. The belt may toothed.

The apparatus may comprise a jig for holding the article to be tested. The apparatus may comprise a platform for supporting the article to be tested. The platform may be height adjustable. The platform may comprise one or more fixtures to retain the article to be tested relative to the platform. The fixtures may comprise a clamp and/or a stop.

The controller may be a microcontroller and may be programmable. The apparatus may comprise a user interface by which a user can control the controller. This may comprise a key pad and display, or a touch screen or an interface for connection to a personal computing device. The controller may be arranged to record and/or display the current drawn by the motor relative to movement of the actuator or time. The current may be determined as the current delivered or intended to be delivered by the controller, since the controller is supplying current to the motor the value of the current is already known by the controller. Or the current may be determined by a current sensor.

The testing apparatus may be for use in peel strength testing or tear testing and/or for performing peel strength testing to determine the force required to remove a film lid from a container.

According to a second aspect of the invention there is provided a method of performing peel strength testing to determine the force required to remove a film lid from a container comprising the steps of providing testing apparatus according to the first aspect invention, with or without any of its preferred features;

using the actuator to peel a film lid from a container; and noting the current drawn by the actuator and/or speed of the actuator during removal of the lid.

The method may comprise the step of determining the force applied by the actuator during the test and comparing the force with one or more thresholds thereby to determine if the film lid was sealed to the container in a satisfactory manner. This may involve comparing the applied force, and/or a mean applied force, to a minimum threshold and/or a maximum threshold.

The method may comprise the step of comparing the force applied during different parts of the test to associated thresholds, thereby allowing different parts of the test to be compared to different thresholds.

The test may be divided into initial, intermediate and final parts. The initial and final parts may include peaks of force require to initiate and end removal of the film lid from the container. The peak force applied during the initial and final parts of the test may be compared to thresholds. The mean force applied during the intermediate part of the test may be compared to thresholds. Alternatively or additionally maximum and minimum forces applied during the intermediate part may be compared to thresholds.

The method may include determining that a lid was not sealed in a satisfactory manner in the event that a maximum or mean force does not exceed a minimum threshold, or exceeds a maximum threshold.

Some or all aspects of the method may be performed automatically or semiautomatically by the testing apparatus.

In a further aspect the invention also provides a testing apparatus for performing peel strength testing to determine the force required to remove a film lid from a container, the apparatus being arranged to determine the force required throughout removal, to compare the force against one or more predetermined thresholds and to indicate that the container has failed a test if the measured force does not meet the, any or each threshold.

The testing apparatus may be according to the first aspect of the invention or it may differ. For example and alternative apparatus comprises a suitable actuator for applying a force to remove a film lid from a container and a load cell arranged to measure the applied force.

The testing apparatus may compare the force to a minimum threshold and/or a maximum threshold. The testing apparatus may be arranged to determine the mean force applied over at least part of the test and compare it to a minimum and/or maximum threshold. The testing apparatus may be arranged to compare the force applied during different parts of the test to associated thresholds, thereby allowing different parts of the test to be compared to different thresholds.

The test may be divided into initial, intermediate and final parts. The testing apparatus may be arranged to identify the peak force applied during the initial and final parts of the test and compare these forces to thresholds. The testing apparatus may be arranged to determine the mean force applied during the intermediate part of the test and compare this to thresholds. Alternatively or additionally the apparatus may be arranged to determine maximum and minimum forces applied during the intermediate part and compare these to thresholds.

Detailed Description of the Invention

In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 is a side view of testing apparatus;

Figure 2 is a part cut away side view of the apparatus of figure 1;

Figure 3 is a left side view of the apparatus of figure 1;

Figure 4 is an enlargement of a part of figure 1;

Figure 5 is an enlargement of a part of figure 1;

Figure 6 is an enlargement of a part of figure 1 showing the apparatus in use; and

Figure 7 is a graph displayed by the apparatus of figure 1 showing force recorded by the apparatus against time during removal of a film lid from a container.

References to upper and lower and like terms refer to the apparatus when oriented as shown in the drawings (which is the orientation in which it is normally intended to be used) but should not be otherwise taken as limiting.

Referring to the drawings, a film lid testing apparatus, generally 1, comprises a base 2, a stage 3, an actuator system 4 and a grip 5.

The base 2 is flat, rectangular and made of plate metal. Three pairs of plastic feet 6 provided on the lower surface of the base 2 prevent the base 2 from slipping when the apparatus is supported by a surface.

The stage 3 comprises an upright post, a platform 8, a first fixture 9 and a second fixture 10.

The post is cylindrical and comprises an elongate body 7 and a top cap 11. The lower end of the elongate body 7 is attached to the upper surface of the base 2 adjacent to one of its shorter sides. The top face of the post comprises a threaded hole. The top cap 11 comprises a disc and a bolt 12. The disc is substantially the same diameter as the elongate body 7 and comprises a central hole which aligns with the threaded hole in the elongate body 7. The bolt 12 is screwed into the threaded hole through the disc to connect the disc to the elongate body 7 whilst allowing a gap between the disc and elongate body 7 within which a part of the first fixture 9 is received.

The platform 8 comprises a flat, rhomboid plate with a cylindrical collar 13 extending from one corner. The central axis of the cylinder extends substantially perpendicularly to the surface of the plate. An elongate slot 14 extends along the major axis of the plate from about mid-way along the axis to a point adjacent the corner of the plate opposite to that from which the collar extends. The collar 13 is sized to pass over the post 7 with a close sliding fit so that the platform 8 can be raised and lowered relative to the base 2. The collar 13 is provided with a threaded hole extending through its side wall and a locking bolt 15 extends in the threaded hole enabling the platform 8 to be secured relative to the post at a chosen height over the base 2.

The first fixture 9 comprises a clamp and a rearwardly extending portion received between the elongate body 7 and top cap 11 of the post so that the first fixture 9 is rotatably and releasably secured adjacent the top of the raising post.

The clamp comprises upper 16 and lower 17 jaws formed from a single piece of resilient metal and having opposing teeth. The jaws 16, 17 are connected at their rear ends and resiliently biased to an open position at their unconnected ends. Coaxial, circular holes are formed through said upper 16 and lower jaws 17. A threaded rod 21 extends through the coaxial holes. An over-centre cam assembly 22 is connected at one end of the threaded rod 21 and a nut 23 is connected at the opposite end. This forms a clamp for urging and locking the jaws 16, 17 towards each other so as to grip a material to be tested between the teeth. In use, with the over-centre cam 22 in an unlocked position, the nut 23 should be threaded sufficiently onto the rod 21 so that when the overcentre cam 22 is rotated to a locked position the jaws 16, 17 are urged together by a desired amount.

The tooth of the upper jaw has a stepped edge. The tooth of the lower jaw has a flat edge. When the jaws 16, 17 are urged together the edge of the tooth of the lower jaw contacts a front part of the tooth of the upper jaw and the stepped part of the tooth of the upper jaw extends behind the tooth of the lower jaw.

The second fixture 10 forms a stop and comprises a V-shaped plate 18 with an upright elongate post 19 positioned at each tip of the V. Each post comprises a cylindrical body with a groove about its circumference adjacent its free end. A rubber O-ring 20 is positioned in the groove to provide a resilient, high-friction surface. A threaded rod 24 extends through a hole formed in the V-shaped plate near its vertex and the slot 14 in the plate of the platform 8. An over-centre cam assembly 25 is connected at one end of the threaded rod and a nut 26 at the other, enabling the second fixture 10 to be releasably clamped to the platform body 8.

The actuator system comprises two spaced apart pulleys 27 mounted in and adjacent opposite ends of an elongate housing 28 having a generally square cross-section. The pulleys 27 each lie in substantially the same plane and have substantially parallel axes of rotation. An endless toothed belt 29 extends between the pulleys 27. The housing 28 is supported on a pair of legs 30.

Each leg 30 comprises an elongate body, a foot 31 extending perpendicularly to the body and an arm 32 spaced above and parallel to the foot 31. Each foot 31 is mounted to the upper surface of the base 2, and the legs 30 are parallel to one another and the shorter sides of the rectangular base 2. The legs are spaced from one another by around half the length of the housing 28.

The housing 28 extends substantially the full length of the base 2 and perpendicular to the legs 30. A slot 33 is provided along substantially the length of a lower wall of the actuator housing 28 in the plane in which the pulleys 27 lie. The belt 29 extends adjacent the slot 33 inside the housing 28. A hook 34 attached to the belt 29 extends through the slot 33 and toward the base 2.

The actuator system further comprises a servomotor 35 comprising a drive shaft and encoder, a micro controller 36 and a user interface comprising a keypad 37 and a display screen 38. Alternatively and/or additionally the controller and/or user interface may be implemented by a programmed computer such as a PC.

The drive shaft is connected to one of the pulleys 27 so the servomotor 35 can drive the pulley, and thus the belt 29, to cause the hook 34 to move substantially linearly to and fro along the slot 33 in the housing 28.

The controller 36 controls the current supplied to the servomotor 35 and is arranged to vary the current supplied in response to changes in rotational velocity of the drive shaft as measured by its encoder. The controller 36 additionally records the current supplied to the servomotor 35 as a function of position of the drive shaft and/or time and stores it in a memory which forms part of the controller 36.

This information may be displayed on the screen 38 as a table or graph or some other suitable form or may be transmitted to a computer or other device via a suitable hard wired or wireless connection.

The grip 5 is connected to the hook 34 fastened to the belt 29 by a length of wire 39 with a loop formed in each end. One loop is passed over the hook 34 of the belt 29 and the other loop over a hook 40 comprised in the grip 5.

The grip 5 further comprises a clamp the rear of which is connected to the hook 40. The clamp comprises upper 41 and lower 42 jaws formed from a single piece of resilient metal and having opposing teeth. Respective circular, coaxial holes extend through the jaws. The hole in the lower jaw is threaded and the hole through the upper jaw is not threaded and of a slightly larger diameter than that through the lower jaw. The jaws are connected at their rear ends and resiliently biased to an open position. A bolt 43 having a threaded metal body and thumb wheel head extends through the aperture in the upper jaw and into the aperture in the lower such that tightening the bolt draws the two jaws together against their resilient bias. The opposing teeth comprise flat mating faces so that, when the teeth are urged into contact the mating faces are flush. This construction allows for delicate objects, such as the film lid of a film-sealed container, to be held by the grip 5 without being cut or weakened.

In operation a container 44 with a film lid 45 to be tested is placed on to the platform 8. In the example shown in figure 6, the container 44 has a rectangular cross section and tapers inwardly from a rim to its base. A lip protrudes outwardly from the rim. The film lid 45 is heat sealed to the rim with an edge of one corner free to facilitate gripping and removal of the lid 45 by a user. Such containers are well known and so will not be described in further detail.

If necessary the platform height is adjusted by loosening the locking bolt 15 and sliding the collar 13 up or down the post 19 so that the lip of the container is adjacent the opening between the jaws 16, 17 of the first fixture 9. The locking bolt is then tightened to secure the platform at the desired height.

The lip of the container at the corner with the free corner of film lid is then clamped into the first fixture 9 with the corner of the rim abutting the protrusion of the tooth extending from the upper jaw 16. This helps ensure that the rim of the container is not pushed into the clamp such that the film lid is undesirably gripped by the fixture. This construction also aids repeatability of positioning.

If necessary, the platform height may be adjusted to ensure that the base of the container sits flat on the platform when the lip is clamped in the fixture.

The second fixture 10 is now urged along the slot 33 in the platform to a position where the O-rings 20 contact each side of the corner of the container opposite to the corner held in the first fixture 9. The second fixture 10 is secured in position by operating the cam assembly 25.

Together the first and second fixtures 9,10 secure the container 44 against sliding movement on the platform 8, and particularly against sliding movement in the direction of the slot 33 in the housing 28. It will be appreciated that the first and second fixtures 9, are capable of securing containers with a variety of different shapes in this way, as well as securing containers in a repeatable way facilitating comparison of the results of testing multiple different containers.

If necessary, a user causes, via the user interface, the actuator system to drive the hook 34 to the end of the housing 28 nearest the stage 3 as shown in figures 1 and 2. The free corner of film lid is then placed between the jaws 41, 42 of the grip 5 and the bolt 43 tightened so as to clamp the film lid.

The user then requests a test cycle via the user interface.

The test cycle is automatically implemented by the controller 36. The controller 36 initially counts down a delay timer. When the predetermined time has elapsed the controller accelerates the servomotor 35 to predetermined rotational velocity and then maintains it at that rotational velocity, causing the hook 34 to move towards the opposite end of the housing 28 at a constant linear velocity. The preferred velocity is about 2.6 m/s, although velocities in the range 1.5 to 3.0 or 3.5 m/s are also suitable.

Moving the hook 34 in this way peels the film lid 45 from the container 44 initially applying a force to the lid 45 at an angle of about 45 degrees (or at least with an angle in the range 40 to 50 degrees) to the horizontal. This simulates a user’s action in removing a lid from a container.

As the film lid 45 is removed from the container 44, the angle at which force is applied to the lid will decrease, depending on the size of the container.

The force required to continue peeling the lid 45 will typically vary owing the changes in adhesion strength between the lid 45 and container 44 and changes in the width of the bond between the lid 45 and container 44 at the point at which the lid 45 is being separated from the container 44. To maintain movement of the hook 34, and so servomotor 35, at a substantially constant velocity the controller 36 varies the current supplied to the servomotor 35. The supplied current and cumulative position of the servomotor drive shaft and/or time elapsed is monitored during the test cycle and the magnitude of the current drawn stored every 100ms in the controller’s memory. Operation of the motor terminates when the hook 34 reaches the opposite end of the housing 28 or when the film lid 45 is removed from the container 44. This can be achieved by programming the required travel distance or time of the hook 34 to remove the lid 45 and stopping the servomotor 35 when the hook 34 has travelled the required distance or for the required amount of time, or by detecting a change in current required to maintain the constant rotational velocity of the drive shaft when the film lid 45 is fully removed from the container 44 which will be characterised by a sudden drop in the required current.

The data collected and stored in memory may then be displayed on the user interface. The data can be shown as a plot of time or distance against current or force. Figure 7 shows an example of a plot of time (in ms) along the horizontal axis against force (in g/f).

The current consumed by an electric motor is proportional to the torque delivered by the motor and so, in the apparatus, to the force applied by the hook 34. Therefore, the instantaneous current supplied to the motor during the test cycle is proportional to the bond strength of the film lid to the container at the time or position. With appropriate calibration, force can be determined from the current drawn by the motor. Even without calibration, variations in current drawn by the motor usefully represent variations in bond strength as the lid is peeled from the container.

The apparatus could be calibrated, for example, connecting the hook 34 to a line which extends over a pulley and connects to a mass with a known value, so that movement of the hook raises the mass. Repeated measurements of the motor current required to raise the mass and different known masses, or no mass, can be made to determine an acceptable accurate calibration constant (or function) relating current to force applied by the hook.

The plot of figure 7 is characteristic for this type of container. Initial movement of the hook away from the container takes up any slack in the line 39 and free end of the film lid 45 to which the line is connected by the grip 5. This usefully allows the servo motor to accelerate from rest to its running speed before any force is applied to remove the film lid from the container. When the slack is taken up the force applied by the hook 34 rises sharply to an initial peak 46. This is the force required to begin peeling the lid from the container to a point where the width of the bond between the lid and the container at the point of peel reaches a maximum at the corner of the container. Beyond that, the width of the bond at the point of peel reduces to a roughly constant value as the lid is peeled from adjacent sides of the container. As such the force applied by the hook falls from the initial peak and then fluctuates over the course of the peel. Fluctuations at this stage represent variations in the strength of the bond of the lid to the container along its edges owing to the quality and/or width of the bond. Towards the end of the peel the force rises sharply to a second peak 47 as the remaining corner of the lid is peeled from the container. At this point the width of the bond at the point of peel increases again as the lid is peeled from the corner of the container. Finally the force drops sharply as the width of the bond reduces and the lid is removed from the container.

This information enables a user to obtain a good understanding of the quality and acceptability of a particular bond. To facilitate determining if a particular bond is acceptable it is useful to formally characterise the bond and determine if certain characteristics of the bond meet predetermined criteria.

The apparatus is further arranged to determine or assist a user in determining certain characteristics of the bond of a film lid to a container and to automatically determine if these, and the bond as a whole, fall within certain predetermined acceptable thresholds.

To do this the controller is arranged to determine parts of the peel strength data for a particular test relating to the initial peel, intermediate peel and final peel. These parts are shown on the graph of figure 7 as 48 (initial peel) being up to the first 1000ms of elapsed time into the peel, 49 (intermediate peel) being from 1000 to 6000ms and 50 (final peel) being from 6000ms to 8000ms. The boundaries separating the three parts may be selected by a user and provided to the controller before or after completion of the test. One or more sets of data identifying boundaries between parts of interest of peel test results may be stored by the controller for selection by a user. These may for example relate to different types of container, for example different sizes and shapes, and may be stored in association with information relating to the type of container to which the relate. This information may be displayed by the controller via the display 38 to enable a user to select a set of data appropriate to the type of container being tested.

The controller is further arranged to determine the highest force applied during the initial and final parts of the peel and to calculate the mean force applied during the intermediate part of the peel. These three values are then compared with respective minimum and maximum thresholds relating to each parts of the peel. These thresholds are represented by heavy lines 51 on figure 7. These thresholds may be entered into the controller by a user. The controller may store different sets of thresholds relating to different types of container and/or intended uses of a container. For example, thresholds for a satisfactory seal may vary according to container size and type, the material of the container and/or its film lid and the product the container is intended to contain. Each set of thresholds may be stored together with a description of a container type and/or application to which it relates. This information may be displayed by the controller via the display 38 to enable a user to select a set of thresholds appropriate to the container being tested. Threshold data may be stored together with data identifying the boundaries of the different parts of the peel of interest discussed above so that both this data and thresholds to be applied may be chosen by a user via a single selection.

The controller 36 determines if the peak force values in the initial and final parts of the peel fall within their associated thresholds. If not, the controller indicates that either or both parts of the peel are considered a fail. The controller also determines if the mean force applied during the intermediate part of the peel lies within the associated thresholds. If not, this part of the peel is considered a fail. If any part of the peel is considered a fail then the peel as a whole is considered a fail and so the bond of the lid to the container is considered unsatisfactory.

The enables a user, and in particular a relatively unskilled user, to test a container against predetermined criteria to establish if the bond of the lid to the container is satisfactory, with the apparatus providing a simple yes or no answer. Where the container is determined to be unsatisfactory additional data may be obtained from the apparatus to indicate which part or parts of the lid seal did not meet the necessary thresholds, and to look at the peel strength plot as a whole. This is useful in identifying, and thus rectifying, the cause of the seal being unsatisfactory.

In another embodiment the controller determines the maximum and minimum forces measured during the intermedia part of the peel and determines if these values fall outside the associated thresholds. If so, that part of the peel is considered a fail.

The apparatus provides a convenient and repeatable way to measure the force required to peel a film lid from a container and to determine if the bond of the film lid to the container is satisfactory for a chosen purpose. The apparatus can accommodate a wide variety of types and sizes of container, with the adjustable platform enabling the pull to remove the lid to start from the same position. The test is performed with the container horizontal so that any foodstuff in the container is unlikely to spill, and in a manner which repeatably and substantially reproduces the action of a user. Using current drawn by the servomotor to measure the force required to remove the lid is a simple and cost-effective way to measure the force which minimises the number of components required.

The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims. For example in the described embodiment the controller is arranged to drive the servomotor at a substantially constant speed and the current drawn or supplied to the motor is determined in order to measure the force applied by the motor. In an alternative embodiment the controller could supply a constant voltage to the motor and the speed of the motor could be measured in order to determine the force applied by the motor. In each case a knowledge of a characteristic of the electrical power supplied to the motor and its speed are used to determine the force or relative force applied by the motor.

Claims

1. A testing apparatus comprising an electrically powered actuator arranged to apply a force to an article to be tested and a controller, wherein the controller is arranged to drive the actuator and determine the current drawn by the actuator and/or the speed of the actuator, thereby to determine changes in the force applied by the actuator during its operation.

2. A testing apparatus as claimed in claim 1 wherein the controller is arranged to drive the actuator at a substantially constant speed and determine the current drawn by the actuator.

3. A testing apparatus as claimed in either claim 1 or 2 claim comprising a connector arranged to connect to the article to be tested and thus enable to actuator to apply a force to the article to be tested.

4. A testing apparatus as claimed in claim 3 wherein the actuator is arranged to move the connector through a linear path.

5. A testing apparatus as claimed in claim 4 wherein the connector is moved through a substantially horizontal path.

6. A testing apparatus as claimed in any of claims 3 to 5 wherein the connector is connected to a belt or chain and the actuator is arranged to drive the belt or chain.

7. A testing apparatus as claimed in any of claims 3 to 6 wherein the connector comprises a clamp having flat mating faces.

8. A testing apparatus as claimed in any preceding claim wherein the actuator is a servomotor.

9. A testing apparatus as claimed in any preceding claim comprising a platform for supporting the article to be tested.

10. A testing apparatus as claimed in claim 9 wherein the platform comprises one or more fixtures to retain the article to be tested relative to the platform.

11. A testing apparatus as claimed in any preceding claim wherein the controller is a microcontroller.

12. Atesting apparatus as claimed in any preceding claim comprising a user interface by which a user can control the controller.

13. A testing apparatus as claimed in any preceding claim wherein the controller is arranged to record and/or display the current drawn by the actuator relative to movement of the actuator or time.

14. A testing apparatus as claimed in any preceding claim wherein the current is determined as the current delivered or intended to be delivered by the controller.

15. A testing apparatus as claimed in any of claims 1 to 13 wherein the current is determined by a current sensor.

16. A testing apparatus as claim any preceding claim for use in peel strength testing or tear testing.

17. A testing apparatus as claimed in any preceding claim for performing peel strength testing to determine the force or relative force required to remove a film lid from a container.

18. A method of performing peel strength testing to determine the force required to remove a film lid from a container comprising the steps of

a. providing testing apparatus according to claim 17;

b. using the actuator to peel a film lid from a container; and

c. noting the current drawn by the actuator and/or speed of the actuator during removal of the lid.

19. A method as claimed in claim 18 comprising the step of determining the force applied by the actuator during the test and comparing the force with one or more thresholds thereby to determine if the film lid was sealed to the container in a satisfactory manner.

20. A method as claimed in claim 19 comprising the step of comparing the applied force to a minimum threshold and/or a maximum threshold.

21. A method as claimed in claim 19 or 20 comprising the step of comparing a mean force applied over at least part of the test to a minimum and/or maximum threshold.

22. A method as claimed in any of claims 19 to 21 comprising the step of comparing the force applied during different parts of the test to associated thresholds, thereby allowing different parts of the test to be compared to different thresholds.

23. A method as claimed in claim 22 wherein the test is divided into initial, intermediate and final parts and comprising the step of comparing the peak force applied during the initial and final parts of the test to thresholds.

24. A method as claimed in claim 23, wherein the test is divided into initial, intermediate and final parts, and comprising the step of comparing the mean force applied during the intermediate part of the test to one or more thresholds.

25. A testing apparatus for performing peel strength testing to determine the force required to remove a film lid from a container, the apparatus being arranged to determine the force required throughout removal, to compare the force against one or more predetermined thresholds and to indicate that the container has failed a test if the measured force does not meet the, any or each threshold.

26. A testing apparatus as claimed in claim 25 arranged to compare the force or mean force applied over at least part of the test to a minimum threshold and/or a maximum threshold.

27. A testing apparatus as claimed in either of claims 25 or 26 arranged to compare the force, or mean force, applied during different parts of the test to associated threshold or thresholds, thereby allowing different parts of the test to be compared to different thresholds.

28. A testing apparatus as claimed in claim 27 wherein the test is divided into initial, intermediate and final parts.

29. A testing apparatus as claimed in claim 28 arranged to identify the peak force applied during the initial and final parts of the test and compare these forces to thresholds and/or to determine the mean force applied during the intermediate part of the test and compare this to thresholds.

30. A testing apparatus as claimed in any of claim 25 to 29 comprising a testing apparatus as claimed in any of claims 1 to 17.