WO2005028312A1

WO2005028312A1 - Heat sealing machine

Info

Publication number: WO2005028312A1
Application number: PCT/GB2004/004036
Authority: WO
Inventors: Richard Michael Ireland
Original assignee: Porvair Sciences Limited
Priority date: 2003-09-22
Filing date: 2004-09-22
Publication date: 2005-03-31
Also published as: GB0322165D0

Abstract

A heat sealing machine for sealing microplates and trays with a sealing film. The machine comprises a sealing film source (3), a feed arm (5) connected to a film feed shoe (20), and a heat sealing area which comprises a plate holding device (10), a hot plate (8) and film cutting means (29), in which the film feed shoe feeds film from the sealing film source to the heat sealing area and which can be moved by means of the feed arm between a loading and operating position.

Description

Heat Sealing Machine

The present invention relates to the sealing of microplates and trays commonly used in numerous applications in the life science industry.

Microplates are in wide use in laboratories for performing chemical assays and sample storage across a wide range of technologies, but in particular in the life sciences. It is sometimes necessary to cover or seal the microplates when the samples in the microwells are to be stored. Samples may need to be stored at room temperature or at lower temperatures, either refrigeration or freezer temperatures (-80°C), and it is essential that the seal is maintained at these temperatures.

One method of sealing the microplates is to use an adhesive film and place it over the microplate and apply pressure causing the adhesive to form a seal between the top surface of the microplate and the film.

Another method of sealing microplates is to use a heat seal. Generally, a polymer film is placed on top of the microplate and heat is applied through a hot plate on top of the film. The heat will soften the film and 'melt' it at the interface between plate and film. Once cooled, the film will act as a leak proof seal on top of the microplate.

Typically, such heat sealing instruments are available in two types. Firstly there are manual systems where an appropriately dimensioned piece of film is sealed to the microplates by manually holding down a hot plate on a single piece of film which has previously been cut to size and placed over the microplate. This is a labour intensive process and is not suitable for high volume situations where a number of plates need to be sealed.

Secondly there are automatic systems where a reel of film is used and is cut into sections during operation, the hot plate for sealing the film being operated by mechanisms within the instrument. Automatic systems are commonly used when a high throughput of sealed plates is required. The speed of sealing cycle time in these units is therefore very important.

However, the automatic systems of the prior art suffer problems which slowdown operation. Firstly, the method of loading the sealing film is difficult and lengthy. It often results in the delicate film being creased which in turn makes it less suitable for use in sealing microplates as it does not form a tight seal over the whole plate or it may jam and block the machine. It is also necessary to allow the system to cool before the film can be replaced. Secondly, the prior art systems operate "in-out" shuttle systems where the plate to be sealed is placed on a shuttle and moved into the machine to have the film sealed to the top of the plate. It is then shuttled out of the machine when the sealing process is complete.

An object of the present invention is to provide a machine into which, the sealing film can be more easily and quickly loaded to reduce down time while the film is loaded.

A further object of the invention is to increase the throughput of the machine.

According to one aspect of the present invention there is provided a heat sealing machine comprising a sealing film source, a feed arm connected to a film feed shoe, and a heat sealing area which comprises a plate holding device, a hot plate and film cutting means, in which the film feed shoe feeds film from the sealing film source to the heat sealing area and which can be moved by means of the feed arm between a loading and operating position.

In one embodiment the film feed shoe includes one or more film gripping means. A first means may be a physical grip such as that provided by a spring- loaded lever and gripper means. A second means, which may be present in addition to the first, may be one or more friction plates which control the movement of the film through the feed mechanism during operation using a light frictional gripping force. In another embodiment the feed shoe may be provided with both film gripping means. The physical grip may hold the film in position while the shoe is moved from the loading position to the operating position and may then be released. The second means may control the movement of the film through the feed shoe in operation.

According to another aspect of the present invention, there is provided a heat sealing machine comprising a sealing film source, a film feed shoe, and a heat sealing area which comprises a plate holding device, a hot plate and film cutting means, in which the plate holding device is mounted to move rotationally within the heat sealing area. The plate holding device may have positions for two or more plates simultaneously such that one plate can be loaded or unloaded while another is being sealed. The plate may further have three or more positions such that there may be one position for loading, one for sealing and one for unloading thereby increasing the throughput of the machine considerably.

The plate holding device is arranged such that it may hold a range of multiwell pates, including 96 well plates and 384 well plates. The plates may be held in place by any suitable means, for example raised portions on the top surface of the plate, or by recesses in the plate in which the microplates sit. The plate holding device may be driven rotationally by means of a step motor operated by central control means.

The present invention also extends to a method of sealing a microplate in which a microplate is loaded onto a plate holding device which is then rotated into position in a heat sealing machine under a hot plate, sealing film is fed by way of a film feed shoe to the heat sealing area where it rests above the microplate to be sealed, the film is secured to the microplate by means of heat applied directly through the hot plate and is cut by cutting means. The method may further include the steps of loading and unloading microplates from the plate holding device while further microplates are being sealed.

Another aspect of the present invention is a method of loading sealing film to a heat sealing machine, in which a feed arm carrying a film feed shoe is moved from an operating position to a loading position, a clamp on the feed shoe is unlocked to reveal a film track, sealing film is placed onto the track, the clamp is replaced with a slight excess of film protruding at the front, the clamp activating gripping means and the feed arm is returned to the heat sealing machine.

Optional features discussed above in connection with the apparatus apply equally to the method.

The invention may be put into practice in a number of ways and one embodiment is shown here by way of example with reference to the following figures, in which:

Figure 1 is a perspective view of the heat sealing machine in the operating position; Figures la and lb show respectively schematic views of the arrangement in the heat sealing area;

Figure 2 is a perspective view of the heat sealing machine in the film loading position; Figure 3 is a perspective view of the feeder arm and feeder shoe in the film loading position;

Figure 4 is a perspective view of the feeder arm and feeder shoe in the film loading position with the clamp open and film being fed into the shoe;

Figure 5 shows an elevation view from the side of the feed shoe being fed with film;

Figure 6 is an elevation view from the side of the feed shoe in the operating position;

Figure 7 shows a perspective view of the plate holding device from above; and

Figure 8 shows a plan view from below of the plate holding device of figure 7.

Figure 1 shows a heat sealing machine 1 in the operating position. The machine comprises a roll of sealing film 3 which is fed via a feed arm 5 to a heat sealing area 4. In the heat sealing area 4 there is a hot plate (not shown in figures 1 and

2) which is a standard hot plate for activating the sealing mechanism between the thin polymer sealing film and the microplate. There are also film cutting means (not shown in figures 1 and 2) for cutting the film to the appropriate length for the microplate to be sealed.

Figures la and lb show schematically the arrangement of the microplate 2, the film 30, the hotplate 8, a film grabber 27, suction pipes 28 and cutting wheel 29. The end of the film 30 is grabbed by the film grabber 27 and pulled out over the waiting microplate. The grabber moves the film 30 a pre-determined distance for the dimension of plate which is being sealed. The system also includes a set of sensors (not shown) which can send a signal to the film grabber to stop or continue pulling if the length of film released is not sufficient to cover the microplate. The film 30 is held up by suction pipes 28 so that the cutting wheel 29 can move transversely across the film 30 and cut off a suitable length for the microplate being sealed. The suction is then stopped and the hot plate 8 descends to seal the film 30 over the microplate 2.

The heat sealing system is controlled by means of programmable control means 7 which can vary the heating time and temperature and therefore also the speed of rotation of the plate holding means.

The microplate 2 is carried to the heat sealing area 4 by means of a plate holding means, in this embodiment a turntable 10. Referring to figures 7 and 8 the turntable 10 has a number of raised portions 11 (only some of which are labelled for reasons of clarity) on the top surface of the plate to hold the microplates in position. In the embodiment shown the raised portions are arranged such that the turntable can hold three microplates simultaneously. As the turntable rotates in operation, it stops in each of three locations - a loading stationl3, a sealing station 14 and an unloading station 15. The movement of the turntable is controlled by means of a stepper motor 12 and belt 16 which in turn are controlled by central processing means (not shown).

At the loading station a microplate 2 is position on the turntable and is held in place by the raised portions such that the plate does not move. The loading of the microplates may be automated and performed by robotic arms as is known in the art. The turntable is rotated through 120° such that the loaded microplate is now at the sealing station 14 where the film is passed over the microplate and is secured to the plate by heat. The heat sealing may typically take between 1 and 40 seconds depending upon the type of film or foil which is being used and also the structure of the microplate. The temperature of the hot plate can also be varied by manual or automatic control. Typically it is within the range of 150-200°C again depending on the type of film or foil and plate.

Films or foils are usually made of a suitable polymer for example polypropylene, polyester or a polypropylene/polyester laminate. The choice of the film is usually made to take into account the necessary downstream processing of the samples. In some cases it is necessary to be able to easily access the plate, when easy peal film will be required. In other circumstances the primary requirement is that the film seal can be easily pierced with a probe to get a sample out again, when an easy pierce film will be required. In all cases the films chosen will be suitable for the temperature range at which the sample will be stored and this is not the primary driving force behind the selection of the film material.

Once the microplate has been sealed the turntable 10 rotates a further 120° clockwise to an unloading station 15 where the sealed plate is removed and transferred to transporting means (not shown) to be taken away to the fridge, freezer or other suitable storage position. Again, the removal of the sealed microplate from the turntable may be by means of a robotic arm as is known.

Naturally once the system is in operation, all three of these operations can take place simultaneously such that while one microplate is being loaded another is being sealed and a sealed microplate is being removed. Thus the time taken to heat seal one microplate is not "wasted" but used to remove a sealed microplate and load a new microplate to be sealed on the turntable for the next sealing.

This multi-station system considerably increases the throughput of the sealing machine by two or three fold when compared to the prior art systems. Referring to figure 2, the feed arm 5 is more clearly shown. At the end of the feed arm 5 is a feed shoe 20 which is shown in more detail in later figures. The feed arm can be rotated from the operating position as shown in figure 1 to a loading position as shown in figure 2. When the feed arm is in the operating position a protective cover 6 moves up to shield the thin film from external damage.

Referring to figure 3, the feed arm 5, roll 3 of sealing film and feed shoe 20 are more clearly shown. The feed arm 5 can be moved between the operating position shown in dotted lines and a film loading position as shown in bold lines. Once in the film loading position, a clamp 22 may be released to reveal film gripping means. These may comprise spring loaded gripper means 24 and friction fingers 26.

Once the clamp is released, sealing film 30 is pulled manually from the roll 3 and is fed into the film track 21. A sufficient amount of film is pulled to extend slightly beyond the end of the film track such that it can be "grabbed" and pulled through the system for the first sealing once the system is activated. In contrast to prior art systems, the flimsy and fragile film does not have to be carefully fed through holes or slots, which is difficult and time consuming.

In the present invention the film 30 is laid along a track and is then held in place by the activation of the clamp 22. Closing the clamp activates a spring loaded gripper 24. The spring 25 pushes the gripper 24 out against the clamp 22 and secures the film in place while the feed arm is moved from the loading position to the operating position.

As the feed arm 5 is moved to the operating position more film 30 is being pulled from the roll 3 but the spring loaded gripper means securely hold the film. When the feed arm reaches the operating position, the spring loaded gripper means 24 are deactivated and the movement of the film is then controlled by the friction fingers 26 and the film grabber 27 discussed above. Within the gripper, fingers clamp on the film 30 and move backwards over the position of the microplate, pulling the film through the heat sealing unit, and the film is then cut by cutting means 29 as described above.

The friction fingers 26 may be made of thin plastic and they apply a light gripping force to the foil to control the movement through the feed mechanism to a position over the microplate to be sealed. They also serve to prevent any back movement of the film, substantial movement of the film as it is being cut or movement caused by outside influences.

The sealing film loading means discussed above is one way of significantly reducing down- time with such a plate sealer. Since the feeder is swung away from the heat sealing area it is not necessary to wait for the whole system to cool down before the film can be replaced. Further the film is easily fed to the system without having to feed it through small holes or channels where tears in the film or creases can occur.

As discussed in part above, the sealing film may be a foil polypropylene laminate, a foil, clear polyester or a polyester/polypropylene laminate. The selection will depend on the downstream requirements of the sealed microplate. The film is typically between 10-50μm thick and the roll of film may be up to 600m long which would provide sufficient film to seal 5000 microplates before the roll would need to be changed. The heat sealing machine is approximately 580mm high by 580mm deep by 670mm wide when the largest roll of film is attached. Of course, the additional components which may be present to load or unload microplates and to transport them away after sealing may increase these dimensions. However, it can be seen that the unit is of a size which can be easily accommodated on a worktop.

Claims

1. A heat sealing machine comprising a sealing film source, a feed arm connected to a film feed shoe, and a heat sealing area which comprises a plate holding device, a hot plate and film cutting means, in which the film feed shoe feeds film from the sealing film source to the heat sealing area and which can be moved by means of the feed arm between a loading and operating position.

2. A heat sealing machine as claimed in claim 1, in which the film feed shoe includes one or more film gripping means.

3. A heat sealing shoe as claimed in claim 2, in which the film gripping means is a physical grip.

4. A heat sealing machine as claimed in claim 3, in which the physical grip is a spring loaded lever and gripper means.

5. A heat sealing machine as claimed in claim 2, in which the film gripping means comprises one or more friction plates.

6. A heat sealing machine as claimed in claim 2, in which the film gripping means comprises a physical grip and one or more friction plates.

7. A heat sealing machine comprising a sealing film source, a film feed shoe, and a heat sealing area which comprises a plate holding device, a hot plate and film cutting means, in which the plate holding device is mounted to move rotationally within the heat sealing area.

8. A heat sealing machine as claimed in any preceding claim, in which the plate holding device has positions for two or more plates simultaneously.

9. A heat sealing machine as claimed in any preceding claim, in which the plate holding device is configured such that it can hold a range of multiwell plates.

10. A heat sealing machine as claimed in any preceding claim, in which the plates are held on the plate holding device by raised portions on the top surface of the plate.

11. A heat sealing machine as claimed in any of claims 1 to 9, in which the plates are held on the plate holding device by recesses in the top surface of the plate.

12. A heat sealing machine as claimed in any preceding claim, in which the plate holding device is driven rotationally by means of a step motor.

13. A heat sealing machine as claimed in claim 12, in which the step motor is operated by central control means.

14. A heat sealing machine as claimed in any preceding claim, in which the film cutting means comprise a cutting wheel.

15. A heat sealing machine as claimed in any preceding claim, in which plates are loaded and/or unloaded automatically.

16. A heat sealing machine as claimed in claim 15, in which the plates are loaded and/or unloaded by robotic arms.

17. A heat sealing machine as claimed in as preceding claim, in which the sealing film is selected from a polymer.

18. A heat sealing machine as claimed in claim 17, in which the sealing film is selected from polypropylene, polyester or a polypropylene/polyester laminate.

19. A heat sealing machine as claimed in any preceding claim, in which the film is between 10 and 50 μm thick.

20. A method of sealing a microplate in which a microplate is loaded onto a plate holding device which is then rotated into position in a heat sealing machine under a hot plate, sealing film is fed by way of a film feed shoe to the heat sealing area where it rests above the microplate to be sealed, the film is secured to the microplate by means of heat applied directly through the hot plate and is cut by cutting means.

21. a method as claimed in claim 20, in which the plate holding device can accommodate two or more plates simultaneously such that plates may be loaded and/or unloaded while another plate is being sealed.

22. A method of loading sealing film to a heat sealing machine, in which a feed arm carrying a film feed shoe is moved from an operating position to a loading position, a clamp on the feed shoe is unlocked to reveal a film track, sealing film is placed onto the track, the clamp is replaced with a slight excess of film protruding at the front, the clamp activating gripping means and the feed arm is returned to the heat sealing machine.