EP0887262A1

EP0887262A1 - Method and apparatus for sealing a closure of a container

Info

Publication number: EP0887262A1
Application number: EP97201967A
Authority: EP
Inventors: Gerrit A. Van Schouwenburg
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-06-27
Filing date: 1997-06-27
Publication date: 1998-12-30

Abstract

The invention relates to an apparatus and to a method for sealing a closure of a container (1), which closure is formed of closure panels and which closure is provided with inactive sealing agent, comprising the steps of:
i) activating sealing agent by local heating of the closure; and
ii) closing the closure such that the closure is sealed by the activated sealing agent, wherein the local heating of the closure is selective throught mechanical shielding (23,24) during heating, increasing the heat capacity before or during heating and/or cooling before, during or after heating such that when the closure panels forming a pouring sprout in the closed closure of the container is inactive, and to a closed container obtainable with the method and/or apparatus.

Description

The present invention relates to a method and an apparatus for sealing a closure of a container, and to a container closed and sealed using said method and/or apparatus.

Such a container generally is made of paperboard. When a liquid is contained in this container the inner surface is preferably coated with a coating impermeable to said fluid. When the fluid is water the coating consists of paraffin or an aluminum, or plastic, or thermoplastic foil.

The container to be closed and sealed comprises a body and an open end formed by closure panels provided with an inactive sealing agent. The sealing agent is conventionally a thermoplastic material such as polyethylene. Upon application of heat the sealing agent is heated above its softening point such that the sealing agent becomes tacky, that is activated. Contacting another closure panel which may be provided with other (activated) sealing agents and subsequently cooling the sealing agent to below its softening point will result in the formation of a seal inbetween the contacted closure panels.

The afore-mentioned type of container is filled, closed and sealed at a relatively high rate. In order to obtain properly sealed containers at a low degree of seal failure, relatively high temperatures are used. Depending upon the product a froth may develop during filling of the container with fluids. This froth will wet parts to be sealed and interfere with the sealing and closure of the container. Especially when the content of the container consists of milk or a similar milk product which due to the prior processing contains gas such as air, froth will form and impart the formation of a proper seal. This will result in a higher degree of improperly sealed containers. This may be compensated for by further increasing the temperature. This ensures a tight seal but in the end it is very difficult to open the container and form the pouring sprout in order to make the content of the container available for use.

EP-A-0 028 941 discloses the use of a heating head provided with openings such that a horizontal sheet of cold air is formed near the site where activation of sealing agent is to be avoided. However, due to variations in the relative positions of the heating head and the open end of the container to be formed, the efficiency of the shielding with the cold air is also variable due to changes in the interference with the cold air sheet and the heat applied by the heating head.

EP-A-0 546 383 discloses the use of adhesive tape which tape is locally applied at the sites of the closure that are to be sealed.

EP-A-0 699 585 discloses the use of a complex heating head for activating sealing agents according to a complex complement pattern.

It is the object of the present invention to improve the afore mentioned apparatus and method such that the degree of fall out is further reduced while the container can still be properly opened at its pouring sprout without the need of excessive force and preferably without damage of the sprout, which improvement does not relate to the use of a complex heating head or means that interfere with the design or working mode of an existing closing apparatus.

The present invention is based on the insight that the afore mentioned objective can be obtained when in a specific way specific parts of the sealing agent are locally prevented from being activated, respectively is deactivated after having been activated. By using mechanical shielding the inaccuracy of interference of cold air and applied hot air is avoided, increasing heat capacity to a specific site will result in such a lower heating of that part that the sealing agent will not become activated, and cooling will result in a deactivation of sealing agent before sealing and closure.

Accordingly, it is avoided to use additional means for improving the sealing, such as the application of additional sealing agent strips, or adapted sealing apparatus elements, which in the later case may complicate the apparatus and/or interfere with the required high rate of closing and sealing this type of containers. Equipment widely used to close and seal gable-top cartons applies hot air of 200-500°C to heat the top of the carton. The hot air is blown out of a complex pattern of slits or holes and directed onto the locations where a seal must be formed. The design of the heating head aims at a good uniform heating of the surface without heating the surroundings area's excessively. In practice the position of the heating head vis-à-vis the carton changes slightly each time a new container is places under the head, as a result the flow of the air, and in particular the cross-wind velocity, can be badly controlled.

Increasing the air temperature or air velocity to ensure proper sealing, as is often necessary when froth formation interferes with the sealing, will aggrevate this effect, resulting in cartons which can only be opened with difficulty and applying excessive force. In opening such a tightly closed container the pouring sprout is often damaged, rendering pouring difficult.

Accordingly, the present invention provides a method for sealing a closure of a container, which closure is formed of closure panels and which closure is provided with inactive sealing agent, comprising the steps of:

i) activating sealing agent by local heating of the closure; and

ii) closing the closure such that the closure is sealed by the activated sealing agent.

characterized in that

the local heating of the closure is selective through mechanical shielding during heating, locally increasing the heat capacity before or during heating and/or cooling before, during or after heating such that when the closure is closed at least part of the sealing agent of the closure panels forming a pouring sprout in the closed closure of the container is inactive.

The present invention provides also an apparatus for sealing a closure of a container, which closure is formed of closure panels, and which closure is provided with inactive sealing agents, comprising:

i) means for locally activating sealing agent by heating;

ii) means for closing the closure such that the closure is sealed by the activated sealing agent,

characterized in that

the means for locally activating sealing agent comprises mechanical shielding means, heat capacity increasing means and/or cooling means, such that when the closure is closed at least part of the sealing agent of the closure panels forming a pouring sprout in the closed closure of the container is inactive; and
means for avoiding activation of at least part of the sealing agent of closure panels forming a pouring sprout in the closed closure of the container, and/or
means for deactivating at least part of the activated sealing agent of closure panels forming a pouring sprout in the closed closure of the container before closing and sealing the closure.

Finally, the present invention relates to the obtainable closed and sealed container. When at least parts of the closure panels forming the pouring sprout have inactive sealing agents when closing and sealing the closure, the force required to open the container and to form the pouring sprout is relatively low although a proper closing and sealing of the closure of the container is garantueed. Furthermore, the boundary between unactivated and formerly activated sealing agent is relatively sharp.

According to a preferred embodiment the mechanical shielding means comprise a plate, or a flexible element such as a sponge, for covering said part of the sealing agent during heating.

According to another preferred embodiment the increase of the heat capacity or the heat capacity increasing means comprise the application of a medium to or near the closure parts to be shielded having a higher heat capacity than the sealing agent.

According to another preferred embodiment the cooling or cooling means comprise application of a coolant to the closure.

If according to a preferred embodiment the method or apparatus the inactive part of the sealing agent reside at the outer side of the folding closure panel, then closure panels not contributing to the sealing are not mutually adhered and therefore the opening force is further reduced. A still further reduction of the opening force is obtainable when according to a preferred embodiment the inactive part of the sealing agent resides at the middle part or the center of the outer side of the folding closure panel. In a still further preferred method or apparatus the inactive part of the sealing agent resides at the middle and center part of the outer side of the folding closure panel. This means that in the most preferred embodiment there is some active sealing agent in the end part of the outer side folding closure panels forming the pouring sprout. Thereby, an optimum closure of the container is feasible at the lowest increase of the required opening force.

In the alternative or in addition it is preferred that the inactive part of the sealing agent resides at the inner side of the folding closure panel. Accordingly, this inner side is not adhered to the inner side of the lateral closure panel. This results in a pouring sprout not comprising side wall having torn apart innersurface of the container. Preferably the inactive part is either the end part, the middle part or the end part and middle part. Most preferred is the allowance of some active sealing agents at the very center of the inner side of the folding closure panel, because that center side contacts the center side of the facing folding closure panel which does not form part of the pouring sprout. Accordingly, it is avoided that any content of the container may come out during storage and shipment via the opening inbetween these center sides in the folding closure panels.

In the alternative or in addition the inactive part of the sealing agent resides at the inner side of a lateral closure panel facing the inner side of the folding closure panel of the pouring sprout. Again is avoided adherence of closure panel parts which are not required for obtaining a proper sealing of the closure of the container. Accordingly, a relatively low force is required for opening the container.

The avoidance of having active sealing agent at the specified parts of the closure panels, is obtainable in several ways. In the first alternative at those parts activation of the sealing agents present is avoided. In another alternative, at those specific parts activated sealing agent is deactivated prior to closure and sealing of the closure.

Both alternatives have the advantage of providing all folding closure panels with sealing agents, thereby avoiding the use of complex means for only depositing or applying sealing agents or agents preventing sealing at very specific sides at these closure panels.

In the apparatus according to the present invention inhibition of activation of the sealing agent is obtainable by the use of shielding means. These shielding means serve the function of avoiding applied heat in reaching those specific parts of the closure panels forming the pouring sprout. These shielding means may comprise a plate, or a flexible element such as a sponge, for covering said part of the sealing agent, or comprise means for creating a fluidum layer adjacent the part of the sealing agent, which fluidum comprises a gas, such as air and nitrogen, or an aerosol such as steam, vapour or a mist whereby said fluidum creates a local high pressure area steering to outflowing hot air around the shielded area's, and/or absorbs the heat.

According to the other alternative the apparatus comprises means for deactivating sealing agent at the specified parts of the closure panels after activation has taken place at said specific part. These deactivation means may comprise according to a preferred embodiment means for cooling said parts with a coolant, such as air, nitrogen, or an aerosol such as steam or a mist or cooling elements, or means for compressing the filled container or the content such that the container content is raised and heat of said parts of activated sealing agent is dissipated via the raised container content.

Finally, the present invention relates to a closed container obtainable with the method and/or apparatus as disclosed hereinbefore. This closed container is characterized by the presence of inactive sealing agent at the specified part of the closing panels forming a pouring sprout. Sealing agent that was not activated during the closure and sealing procedure is very well detectable either by using an optical microscope or by atomic force microscopy. Both methods show in the inactive sealing agent domains having a regular, generally line-wise appearance and a random unstructured appearance after heating and deactivation. Still, it is observable when opening the pouring sprout whether these specific parts of the closure panels comprised inactive sealing agent during the closing and sealing procedure. If the sealing agent was active it should have adhered to the other side and pressing of tearing part sealing agent would be noticeable. When activated sealing agent was deactivated before closure and sealing, then the deactivated sealing agent is not provided with torn apart pieces of the facing closure panel.

The afore-mentioned and other features and advantages of the method, apparatus and container according to the present invention will be further illustrated in the form of the adjacent non-limitive description, while making reference to the annexed Figures.

In the Figures is:

Figure 1 a gable top container of the type according to the present invention.

Figure 2 in top view (Figure 2A and 2B) and in cross-section (Figure 2C) a method or apparatus comprising means for inhibiting activation.

Figure 3 alternative inhibition means in top view (Figure 3A) and cross-section (Figure 3B).

Figure 4 an apparatus comprising still another embodiment of the inhibition means.

Figure 5 an apparatus for closing a closure comprising deactivation means.

And Figure 6 an apparatus according to the present invention comprising deactivation means comprising container content coolant.

Figure 1 shows a container 1 of the type according to the present invention.

The container comprises a body 2 formed by side body panels 3 and 4. These side body panels 3 and 4 are connected to lateral folding panels 5 and side folding panels 6.

The side folding panel 6 comprises two side panel parts 7 and 8 and a central panel part 9 mutually separated by a score line 10.

The lateral folding panel 5 is connected to a lateral closure panel 11 having a lateral sealing edge 12.

The side folding panel 6 is connected to the folding closure panel 13 having an end part 14, a middle part 15, and a center part 16.

Finally, there is a score line 17 passing through the lateral folding panel 5. This score line facilitates the formation of the pouring sprout which is substantially formed by the side folding panel 6, the folding closure panel 13 and the boundary parts of the lateral folding panel 6 up to the score line 17.

According to the present invention sealing agents may be applied to the inner side of the lateral sealing edges 12, to the inner and outer side of the folding closure panel 18 not forming part of the pouring sprout, and to the facing end parts 14 of the folding closure panel 13. When a seal is formed inbetween these edges 12 and closure panel 18 there is a minimum closure and sealing of the container.

Preferably, there should not be a seal inbetween the facing, middle part 15 and center part 16 of the outer folding closure panel 13 of the pouring sprout because in principal they do not contribute to the sealing of the closure. This applies also to the inner side of the folding closure panel 13 at its end, middle and center part. At the inner center part there may be a seal because it contributes to the sealing of the closure.

With reference to Figure 2, is shown in top view a container 1 according to the present invention. In the opening 19 between the lateral sealing edges 12, the folding closure panel 13 and the folding closure 18 is inserted a heating element 20. Two

additional heating elements

21 and 22 are positioned such that the folding closure panel 13 and folding closure panel 18 lay between the heating element 20 at the respective

additional heating element

21 or 22.

The heating element 20 is provided with shielding element 23 and the additional heating element 22 with shielding elements 24.

Reciprocating the

heating elements

20 and 22, result in shielding the middle parts 15 of the folding closure panel 13.

Heating fluidum (such as hot air) coming out of the

heating elements

20, 21 and 22 allowed to penetrate into the space 41, will result in a softening of the sealing agent because its temperature is raised above its softening point. The shielded middle parts 15 and center part 16 of the folding closure panel 13 will have sealing agent in the inactive state because heat cannot reach these middle parts 15.

When subsequently the container 1 is closed, the middle part 15 of the folding closure panel 13 will not adhere to the inner side of the lateral closure panel 11 nor to the facing part of the folding closure panel 13.

With reference to Figures 3A and 3B, the shielding means consist of sponge material 26 residing between the two

heating elements

22 and 20 thereby avoiding the contact between heating fluidum ejected by the heating element and the middle part 15 and the center part 16 of the folding closure panel 13. This sponge material may be cooled to below the softening temperature of the thermoplastic sealing agent in order to avoid the hot sealing agent to become tacky, the sponge material to become too hot, and/or adherence of the sponge to the sealing agent/carton.

Figure 4 shows another embodiment. In this embodiment the

heating elements

20 and 22 are provided with means 26 for generating insulating fluidum layers 27 and 28 between the

heating elements

20 and 22 and the middle part 15 and center part 16 of the folding closure panel 13. This layer of insulating material may be water droplets, or cooled steam or mist. These means 26 comprise a channel 29 via which the fluidum is supplied to openings 30 facing the

space

31 and 32 between the respective heating element and the folding closure panel 13.

Figure 5 shows another embodiment. In this embodiment the sealing agent applied to the lateral closure panels 11, lateral sealing edges 12, the folding closure panel 13 and the folding closure panel 18 was activated with heating means shown in the afore-mentioned Figures. Subsequently, deactivation means 32 are used to deactivate sealing agent at the folding closure panel 13. At its outer side is deactivated sealing agent in the middle part 15 and the center part 16 using cooled steam ejected from apertures 33. At the inner side activated sealing agent is deactivated only in the middle part 15 of the folding closure panel 13 using cooled steam or mist ejected via the apertures 34. The apertures 33 and 34 are both provided in a coolant emitting block 35 respectively 36 suspending from a traverse 37 connected to a strut 38 through which is passed a line 39 for feeding coolant to the apertures 33 and 34. In stead of the shown deactivation means 32 use can be made of a cooling sponge or cooling plate which is pressed against the inner and outer side of panel 6.

Finally, Figure 6 shows a container 1 having at its inner side an alu-foil coating. Using pressing blocks 40 as deactivation means, the container is compressed and its content raised such that heat is dissipated and the inner side folding panels 6 via the heat conducting alu-foil. Accordingly, sealing agent in the

folding panel

6 and 5 is deactivated before closure and does not participate in the formation of the seal.

Claims

Method for sealing a closure of a container, which closure is formed of closure panels and which closure is provided with inactive sealing agent,
comprising the steps of:

i) activating sealing agent by local heating of the closure; and

ii) closing the closure such that the closure is sealed by the activated sealing agent.

characterized in that

the local heating of the closure is selective through mechanical shielding during heating, increasing the heat capacity before or during heating and/or cooling before, during or after heating such that when the closure is closed at least part of the sealing agent of the closure panels forming a pouring sprout in the closed closure of the container is inactive.
Apparatus for sealing a closure of a container, which closure is formed of closure panels, and which closure is provided with inactive sealing agents, comprising:

i) means for locally activating scaling agent by heating;

ii) means for closing the closure such that the closure is sealed by the activated sealing agent,

characterized in that

the means for locally activating sealing agent comprises mechanical shielding means, heat capacity increasing means and/or cooling means, such that when the closure is closed at least part of the sealing agent of the closure panels forming a pouring sprout in the closed closure of the container is inactive; and

means for avoiding activation of at least part of the sealing agent of closure panels forming a pouring sprout in the closed closure of the container, and/or

means for deactivating at least part of the sealing agent of closure panels forming a pouring sprout in the closed closure of the container before closing and sealing the closure.
Method or apparatus according to claim 1 or 2, wherein the mechanical shielding or the mechanical shielding means comprise a plate, or a flexible element such as a sponge, for covering said part of the sealing agent during heating.
Method or apparatus according to claim 1-3, wherein the increasing of the heat capacity or the heat capacity increasing means comprise the application of a medium near or to the closure parts to be shielded, having a higher heat capacity than the sealing agent.
Method or apparatus according to claim 1-4, wherein the cooling or cooling means comprise application of a coolant to the closure.
Method or apparatus according to claim 1-5, wherein the inactive part of the sealing agent reside at the outer side of the folding closure panel.
Method or apparatus according to claim 6, wherein the inactive part of the sealing agent resides at the middle part or the center of the outer side of the folding closure panel.
Method or apparatus according to claim 6 or 7, wherein the inactive part of the sealing agent resides at the middle and center part of the outer side of the folding closure panel.
Method or apparatus according to claims 1-8, wherein the inactive part of the sealing agent resides at the inner side of the folding closure panel.
Method or apparatus according to claim 9, wherein the inactive part of the sealing agent resides at the end part or the middle part of the inner side of the folding closure panel.
Method or apparatus according to claim 9 or 10, wherein the inactive part of the sealing agent resides at the end part and middle part of the inner side of the folding closure panel.
Method or apparatus according to claims 6-11, wherein inactive part of the sealing agent resides at the inner side of a lateral closure panel facing the inner side of the folding closure panel of the pouring sprout.
Apparatus according to claim 1-12, wherein the shielding means comprise means for creating a fluidum layer adjacent the part of the sealing agent, which fluidum comprises a gas, such as air and nitrogen, or an aerosol such as steam or a vapour.
Apparatus according to claims 1-13, wherein deactivating means comprise means for cooling said parts of the sealing agent with a coolant, such as air, nitrogen, or an aerosol such as steam or vapour, or a mist or cooling elements, or means for compressing the container such that the container content is raised and heat of said parts of sealing agent is dissipated via the raised container content.
Closed container obtainable with the method and/or apparatus according to claims 1-14.