WO2005077774A1

WO2005077774A1 - Container with internal thread and method of its manufacture

Info

Publication number: WO2005077774A1
Application number: PCT/DK2005/000108
Authority: WO
Inventors: Kim R Norland
Original assignee: Kim R Norland
Priority date: 2004-02-18
Filing date: 2005-02-18
Publication date: 2005-08-25

Abstract

A container (1) with a closure portion (5) defining a center axis (13), said closure portion (5) having an outer side (6) and an inner side (4), said inner side (4) having a thread (3), the bottom of the groove of said thread (3) lying on a revolved surface (4), where the thread (3) is divided into a number of segments (7) along the helical path of said thread (3), said thread segments (7) separated by a number of gaps (8), each of said gaps (8) extending in depth at least to said revolved surface (4). In this way a container is provided which is comfortable to the mouth of a person drinking directly from the container. In addition, a container is provided which has low flow resistance and helps to prevent fluid from collecting in the thread. In addition to the container, a cap and a method of producing a container according to the invention is also provided.

Description

Container with internal thread, and method of its manufacture

Field of Invention

The present invention relates to a container with a closure portion defining a center axis, said closure portion having an outer side and an inner side, said inner side having a thread, the bottom of the groove of said thread lying on a revolved surface, a cap for such a container, and a method for manufacturing such a container by means of an injection molding machine.

Background of the Invention

Many beverages are drunken directly from the container in which the beverage is contained. For example, carbonated beverages such as Coca-Cola™ are often consumed directly from the bottle. During consumption of the beverage, the mouth of the consumer is in direct contact with the neck portion of the bottle. Since typical bottles have a neck portion with a closure portion comprising an external thread located directly at the opening of the bottle, this can be unpleasant for the consumer's mouth. In addition, the external thread can easily collect bacteria, other unwanted contaminants, or any other form of microorganism which could lead to contamination or tainting of the beverage or a bad taste for the user.

Description of the Prior Art

One solution to these problems is to form the inner side of the closure portion with a thread instead of forming the outer side of the closure portion with a thread. Since, in this case, the thread is on the inner side of the bottle, the outer side of the bottle can be made smooth. A smooth outer side is more comfortable to the consumer's mouth. In addition, a smooth surface is more resistant to picking up bacteria, contaminants or other forms of microorganisms.

It is known to form the inner side the closure portion of a container with a thread. US patent 1,415,908 provides for a glass jar closure system. US patent 2,026,304 provides for a glass bottle with an internal thread and a pliable stopper. US patent application 2003/0057173 provides a glass wine bottle with an internal thread.

However, the internal threads as provided by the above mentioned patent documents do not lend themselves well to high volume production as is required in, for example, the production of bottles for the carbonated beverage production industry. During the manufacture of beverage containers, such as Coca-Cola™ bottles, bottles are typically formed out of plastic in a two stage forming process. In the first step, a preform is injection molded. The preform comprises the final formed neck portion and an unshaped bottle section. The preform is then inserted in a blow molding machine and the bottle section is blow molded into the final bottle shape.

During traditional molding of preforms, a two-part mold can be used. After the plastic has been injected into the mold, the mold is split into two and the preform can be removed from the mold. This is a very fast process. However, in the injection molding of an internal thread, the molding of the thread occurs inside the neck portion of the preform. It is therefore not possible to split the mold in two and remove the preform directly. Rather, after the mold is split in two, the preform has to be unscrewed from the injection mold. This is a time consuming process. Since production speed is a very important parameter in, for example the carbonated beverage market, internal threads as known are not well suited for this market. Another problem with the- internal threads as known is that while drinking, the fluid flows over the thread. When drinking is stopped, a portion of the fluid can remain trapped in the threads on the inside of the bottle. This can lead to bad taste or bacteria collecting in the thread. In addition, the fluid flowing over the threads creates turbulence in the fluid as it exits the container. This can lead to splashing and/or reduced flow out of the container.

Summary of the Present Invention

A first aspect of the current invention is to provide a container as mentioned in the opening paragraph which is comfortable to drink from.

A second aspect of the current invention is to provide a container as mentioned in the opening paragraph which reduces the amount of fluid which can be trapped in the thread.

A third aspect of the current invention is to provide a container as mentioned in the opening paragraph with low resistance to pouring.

A fourth aspect of the current invention is to provide a container as mentioned in the opening paragraph which agitates the beverage on leaving the bottle thereby increasing the carbon-dioxide release in carbonated beverages .

A fifth aspect of the current invention is to provide a container as mentioned in the opening paragraph which can be manufactured at high production rates .

An sixth aspect of the current invention is to provide a method of manufacturing a container as mentioned in the opening paragraph which does not require expensive and/or complicated machinery. The new and unique way in which the current invention fulfills the above mentioned aspects is by presenting a container as mentioned in the opening paragraph, where the thread is divided into a number of segments along the helical path of the thread and the thread segments are separated by a number of gaps, each of the gaps extending in depth at least to the revolved surface. In this way, the outer side of the closure portion can be made in different shapes and can therefore be made comfortable to drink from.

The segmented thread on the inner side of the closure portion reduces the amount of fluid which can be trapped in the thread. In a continuous thread, a small amount of fluid remains trapped by the thread after pouring. By segmenting the thread, there is less thread in which the fluid can be trapped. In addition, the segmented thread reduces the amount of flow resistance experienced by the fluid when it is poured out of the container. The gaps between the thread segments allow the fluid to flow out of the container with less resistance than if the thread were continuous. This also reduces the amount of splashing and turbulence created by the thread.

The slight agitation of the fluid as it flows over the segmented thread also results in an increase in the amount of carbon dioxide released during the pouring. This increases the fizzing effect of the fluid as it leaves the container. This means that less carbon dioxide needs to be added to the fluid for the same amount of fizzing to be experienced by the person drinking the fluid.

A segmented thread also results in a lower cost during the manufacturing process since the tooling does not have to be as accurate. Slight misalignments in the tooling will not have a negative effect on the form of the thread. In a preferred embodiment of the container a number of said gaps can be divided into at least one set, each of the at least one set of gaps extending along a path, where the angles formed between the tangent vectors of said at least one path and the center axis of the closure portion are in the range from 0° to 60°, preferably from 0° to 30°, and especially from

0° to 15°. This creates channels which run through the thread. These channels allow the fluid to flow through the thread along these channels. This further reduces the amount of flow resistance. The channels also provide paths which allow the fluid trapped in the threads to run out of the threads .

In order to use simpler tooling during the injection molding of the container, a number of the gaps can be divided into more than one set of gaps and the paths along which said sets of gaps extend can be similar in shape but rotated around the center axis of the closure portion. In this way, a number of channels are defined around the circumference of the inner side of the closure portion of the container. In this way, parts of the tooling can slide along these channels. This reduces the demand for either unscrewing the tooling from the formed part or the need for collapsible tooling which is complicated and expensive.

In addition to arranging the gaps along a path, a number of the thread segments can be divided into at least one set, each of said at least one set of thread segments extending along a path, said at least one path being similar in shape to said at least one path along which said at least one set of gaps extend, but rotated around the. center axis of the closure portion.

In order to allow the formed container to be withdrawn from the part without using collapsible tooling, the length of said gaps can be made larger than the length of said thread segments, said lengths being the dimensions of said thread segments and said gaps along the helical path of said thread.

In a preferred embodiment the outer side of the closure portion can be smooth in an area extending from or nearly from the mouth of the container. A smooth outer side will be comfortable to the mouth of the person drinking from the container.

A cap for a container according to the opening paragraph can be manufactured with second sealing means to seal the outer side of the closure portion of the container from contaminants and/or microorganisms. In a preferred embodiment, the second sealing means could comprise a flange on the skirt which forms a seal with a flange on the closure portion of the container. This is a simple arrangement which effectively prevents any form of contaminants or microorganisms from reaching the outer side of the closure portion of the container.

In another beneficial embodiment of a cap the center portion can be hollow and can be covered by a removable lid. In this way, items, such as tokens for a contest, can be placed in the cap.

One well suited method for manufacturing a container according to the invention is by means of an injection molding machine where a form having a core with at least one center part and at least one retractable part is mounted on the machine, injecting melted plastic into the form, cooling the plastic below the solidification point, retracting the at least one retractable part of the core relative to the center part of the core, rotating the core relative to the formed part, said rotation being less than a full rotation of the core, and withdrawing the core from the formed part along a path similar in shape to the path along which the at least one set of gaps extend. This method results in a high output since the formed container does not have to be completely unscrewed from the core. In addition, it makes use of a relatively simple core, instead of a more complex collapsible core.

Brief Description of the Figures

The invention will be explained in greater detail below where further advantageous properties and example embodiments are described with reference to the drawings, in which

Fig. 1 is a schematic perspective representation of a container and a cap according to the invention,

Fig. 2 shows a folded-out view of the thread on the inner side of the closure portion of the container,

Fig. 3 shows the container and the cap seen from the side,

Fig. 4 shows a section view defined by the line IV-IV in fig. 3,

Fig. 5 shows a side view of the top part of a container according to the invention,

Fig. 6 shows a section view defined by the line VI-VI in fig. 5,

Fig. 7 shows a second embodiment of a cap according to the invention,

Fig. 8 shows a collapsible core as is known in the prior art,

Fig. 9 shows the same in a collapsed state, Fig. 10 shows a schematic perspective representation of a core used in an example method of manufacture of a container according to the invention,

Fig. 11 shows a schematic perspective representation of the same in a second state,

Fig. 12 shows a schematic side view of the same,

Fig. 13 shows a schematic section view of the same defined by the line XIII-XIII in fig. 12,

Fig. 14 shows a schematic section view of a second embodiment of a core used in the manufacture of a container according to the invention, and

Fig. 15 shows a section view of the same in a second state.

Description of a Preferred Embodiment of the Invention

Fig. 1-6 show different views of the top section of a plastic bottle 1 used for carbonated beverages such as Coca-Cola™. Fig. 1, 3 and 4 also show a cap 2 which fits the bottle 1 shown in fig. 1-6.

Bottles of the kind used for carbonated beverages typically have a cylindrical closure portion having an outer side with a thread onto which a plastic cap can be screwed. This external thread is uncomfortable for the mouth when drinking from the bottle. In contrast to typical bottles, the inner side 4 of the closure portion 5 of the bottle 1 shown in fig. 1 has a thread 3. The outer side 6 of the closure portion 5 is smooth and therefore does not irritate the mouth when drinking directly from the bottle 1. In the example shown, the closure portion 5 is cylindrical, however other forms, for example conical, could also be used. The outer side 6 of the closure portion 5 can take many different forms. The outer side could also be coated with different coatings. One example is a material called SoftTouch™ which is especially comfortable to the mouth while drinking. Another example could be a dimpled surface or a wavy surface.

By referring to fig. 1 and 4, it can be seen that the thread 3 on the inner side 4 of the closure portion 5 is divided into a number of thread segments 7 which are separated by gaps 8. In order to describe the thread 3 better, fig. 2 shows a schematic view of the thread 3 as it would appear if the cylindrical closure portion were folded out. The solid parallelograms represent the thread segments 7 and the dotted parallelograms represent the gaps 8. As can be seen from fig. 2, the gaps 8 and the thread segments 7 are of approximately equal length. It can also be seen that the gaps 8 and the thread segments 7 are divided into sets 9a, 9b, 9c, 9d, 10a, 10b, 10c, lOd each set containing three thread segments 7 or three gaps 8. Each set extends along a path 11a, lib, lie, lid, 12a, 12b, 12c, 12d. In the current embodiment, as shown in 1, 2 and 4, the paths 11a, lib, lie, lid, 12a, 12b, 12c, 12d are lines parallel to the center axis 13 of the cylindrical closure portion 5.

However, within the scope of the invention, the paths along which the sets of gaps and thread segments are arranged can take many different forms. For example, the paths can form a helical path instead of a straight line. In this case, the tangent vectors to the paths will form an angle to the center axis of the closure portion. A straight path which is parallel to the center axis, as is the case in the example embodiment shown in fig. 1-6, is actually a special case of a helical path where the tangent vectors form an angle of 0° to the center axis. In addition, within the scope of the invention, the gaps and the thread segments could be arranged randomly without being divided into sets following a path.

The paths will be further discussed below where methods of manufacturing of containers according to the invention are discussed.

In the above examples, it is also shown that the gaps 8 are all of a similar length and that the thread segments 7 are all of a similar length. This is useful in certain cases, as will also be discussed further below where methods of manufacturing are discussed. However, similar length is not necessary for the invention. Both the thread segments 7 and the gaps 8 can have different lengths.

In fig. 1, it can be seen that the thread 3 is lying on the inner side 4 of the closure portion 5. The inner side 4 can be described as a revolved surface which is cylindrical. However, the revolved surface on which the threads lie could also take many other forms, such as a conical surface. As can be seen from fig. 1, the bottom of the groove of the thread 3 is located on this revolved surface 4.

The gaps 8 can also be defined by this revolved surface 4, in that it can be understood that a gap is a cut through a thread, the depth of which extends from the top of the ridge of the thread 3 down to the revolved surface 4. In certain cases the cut could extend past the revolved surface 4. In this case, the gaps or cuts would be deeper than the ridges of the threads 3 are high.

Fig. 1 and 4 also show a rim 14 which can be used during the manufacture, the bottling, and the distribution of bottles of this kind. A rim 14 of this kind is known from typical plastic bottles. Fig. 4 shows a section view of the bottle 1 and the cap 2 of fig. 1 as defined by the section line IV-IV in fig. 3. In fig. 4 the details of a cap 2 according to the invention can be clearly seen. The cap 2 comprises a center portion 15 of a cylindrical shape with an external thread 16 which matches the thread 3 on the inner side 4 of the bottle 1. The cap 2 also comprises first sealing means 17 which is a rubber-like seal 17 placed in the top of the cap 2. When screwing the cap 2 onto the bottle 1, the seal 17 is pressed against the top 18 of the closure portion 5 of the bottle thereby sealing the contents of the bottle. The seal 17 could take many different forms. One further example is a seal which is integrated into the cap itself.

The cap also comprises a skirt 19 which covers the outer side 6 of the closure portion 5 of the bottle when the cap is screwed onto the bottle. At the bottom of the skirt 19 is located a second sealing means 20 which prevents any contaminants, bacteria or other forms of microorganisms from reaching the outer side 6 of the closure portion of the bottle when the cap is screwed onto the bottle. This second sealing means 20 comprises a flange 21 on the bottom of the skirt 19 which engages with a flange 22 on the outer side 6 of the closure portion of the bottle. This second sealing means. 20 could take many different forms. One further example of second sealing means could be a skirt of pliable material which tightly grips the entire outer side of the closure section of the bottle when the cap is screwed onto the bottle.

As can be seen from fig. 4, the center portion is hollow. This hollow space 23 can be closed both at the top and at the bottom during the forming process. However, as is shown in fig. 4, the hollow section in this case has been left open at the bottom end. In this case, items, such as tokens for a contest could be placed in the hollow section. A lid (not shown) can then be placed over this hollow center portion 23 in order to seal it from the contents of the bottle. The lid can be a sticker or a rubber plug or one of many other possible devices. Fig. 7 shows a second embodiment of a cap 24 according to the invention. This cap 24 is similar to the cap 2 shown in fig. 4, however, the hollow center portion 23 is sealed at the bottom and opened at the top . The type of cap produced can be changed quickly during the manufacturing process by using a different insert in the mold.

As discussed in the introduction, plastic containers such as those used for carbonated beverages are typically produced in a two-stage process. The first step is an injection molding process and the second stage is a blow molding process. As was also mentioned in the introduction, a thread formed on the inner surface of a cylindrical closure portion is difficult to manufacture at high speed since the container has to be unscrewed from the internal core which forms the thread.

One solution to this problem is to use a collapsible core 25 as shown in fig. 8 and 9. Fig. 8 and 9 show a section view of a collapsible core as known in the manufacturing industry. The collapsible core in this example is comprised of six first parts 26 and six second parts 27. Fig. 8 shows the core in its expanded state and fig. 9 shows the core in its collapsed state. In order to collapse the core, the first parts 26 are retracted in towards the center of the core. Once the first parts have been retracted, the second parts 27 are also retracted in towards the center of the core. When the core is expanded, as is shown in fig. 8, the core defines an external diameter of Dl . When the core is collapsed, as is shown in fig. 9, it has an external diameter of D2 which is less than Dl . By machining a thread into the outer surface of the core in its expanded state, the core can be used to form the thread on the inner surface of the closure section of a container according to the invention. When the core is collapsed the container can be removed without having to unscrew the container from the core.

Use of a collapsible core will result in high production speeds since the container can be removed directly from the mold, just by collapsing the core. However, a collapsible core is a rather complicated piece of machinery. It is comprised of a number of components which need to act in unison. If the alignment of the different components is not correct, the formed thread will be formed poorly. In addition, due to the complex nature of the collapsible core, the core will be a rather expensive piece of equipment. However, since the thread in a container according to the current invention is segmented and separated by gaps, the precision requirements to the core are less. Since the thread is not continuous, small errors in misalignment of the component of the core will not result in steps or misalignments in the formed thread.

Fig. 10-13 show some different views of another example core 28. The core 28 shown in fig. 10-13 is simpler than the core

25 shown in fig. 8 and 9. The top section of a bottle 1 according to the invention is also shown in order to illustrate the relationship between the core 28 and the finished bottle 1. The core 28 shown in fig. 10-13 is comprised of a center part 29 and four retractable parts 30.

Fig. 10 shows the core 28 in the state it is in during the- injection-molding step. As can be seen the retractable parts

30 are not retracted and are an integrated part of the center part 29. Fig. 11 shows the same core 28 but with the retractable parts 30 retracted. Fig. 13 shows a section view of the core 28 as defined by the section line XIII-XIII defined in fig. 12.

When manufacturing a container using the core 28 shown in fig. 10-13, the core 28 would be inserted, in the state shown in fig. 10, into a mold (not shown) which forms the outside of the closure portion. This mold is known from the current method of forming plastic containers. Liquid plastic would then be injected into the mold and cooled until the plastic solidification temperature is reached. The retractable parts 30 of the core 28 would then be retracted, thereby assuming the state as shown in fig. 11. When the retractable parts 30 are retracted, a number of recesses 31 are formed in the core 28. The core 28 is then rotated until the thread segments 7 of the container 1 are centered in said recesses 31. The core 28 can then be withdrawn from the formed container, the mold opened, and the formed container removed.

It should be obvious to the person skilled in the art that the above process is just one of many possible manufacturing processes. It should also be obvious to the person skilled in the art that the steps could be performed in many different orders. In addition, the motions between the mold, the core, and the container could be performed in many different ways. For example, the rotation step could be performed by the formed container being rotated relative to the core, or the core could be rotated relative to the formed container, and so on.

Fig. 14 and 15 show another example of a core 32 which could be used in the manufacture of a container according to the invention. In this case, the core 32 also comprises a center part 33 and four retractable parts 34. However in this case, the retractable parts 34 are retracted towards the center of the core 32. The principle of operation of this core 32 is otherwise identical to the principle of operation of the core 28 shown in fig. 10-13.

In the case of the last two example cores 28,32, it is necessary for the length of the thread segments 7 of the container 1 to be equal to or less than the length of the gaps

8 between the thread segments 7. The gaps 8 will be the same size as the recesses 31 formed in the core 28,32 once the retractable parts 30,34 have been retracted. In order for the core 28,32 to be withdrawn from the formed container, the thread segments 7 of the container 1 have to be able to fit inside the recesses 31 formed in the core 28,32. If the thread segments 7 were longer than the gaps 8, then the core 28,32 could not be withdrawn from the formed container. In order to ensure easy withdrawing, it is best to make the gaps 8 longer than the thread segments 7.

In addition, it is necessary for the paths lla,b,c,d, 12a,b,c,d along which the gaps 8 and thread segments 7 are arranged to be formed in a manner which allows the retractable parts 30,34 to be retracted. A straight path parallel to the center axis, as shown in fig. 1, 2 and 4 is a good example as it allows the retractable parts to be withdrawn straight upwards. Another example would be if the retractable parts 30,34 were formed along a helical path. In this case, the paths 11a,b, c,d, 12a,b, c,d along which the gaps 8 and thread segments 7 were arranged would also have to be helical. If the retractable parts 30,34 were in a helical path, then the retractable parts 30,34 would have to be rotated while being retracted. In the case that the core 25 used is a collapsible core, there are no demands on the spacing or the arrangement of the gaps 8 and the thread segments 7.

It should be obvious to the person skilled in the art that the examples of manufacturing presented above are simplified examples used to illustrate a few different concepts regarding a core for forming the internal thread. The actual manufacturing process used in the manufacturing of a container according to the invention comprises many additional steps and is therefore more complicated. In addition, the example cores presented above are very simple example embodiments. An actual core used in manufacturing will comprise many additional features and be more complicated. Also note that emphasis has been placed on plastic bottles for carbonated beverages. However, the container according to the current invention is not limited to plastic bottles for carbonated beverages . Containers according to the current invention can be produced for all sorts of different applications and in all sorts of different materials. Some examples are pill bottles, motor oil containers, milk bottles, juice containers, etc...

Claims

Claims :

1. A container (1) with a closure portion (5) defining a center axis (13) , said closure portion (5) having an outer side (6) and an inner side (4) , said inner side (4) having a thread (3) , the bottom of the groove of said thread (3) lying on a revolved surface (4), characterized in that said thread (3) is divided into a number of segments (7) along the helical path of said thread (3), said thread segments (7) separated by a number of gaps (8) , each of said gaps (8) extending in depth at least to said revolved surface (4) .

2. A container (1) according to claim 1, characterized in that a number of said gaps (8) are divided into at least one set (9a, 9b, 9c, 9d) , each of said at least one set (9a, 9b, 9c, 9d) of gaps 8 extending along a path (11a, lib, lie, lid) , where the angles formed between the tangent vectors of said at least one path (11a, lib, lie, lid) and the center axis (13) of the closure portion (5) are in the range from 0° to 60°, preferably from 0° to 30°, and especially from 0° to 15°.

3. A container (1) according to claim 2, characterized in that a number of said gaps (8) are divided into more than one set (9a, 9b, 9c, 9d) of gaps (8) and that the paths (11a, lib, lie, lid) along which said sets (9a, 9b, 9c, 9d) of gaps (8) extend are similar in shape but rotated around the center axis (13) of the closure portion (5) .

4. A container (1) according to any one of claims 2 or 3 , characterized in that a number of said thread segments (7) are divided into at least one set (10a, 10b, 10c, lOd) , each of said at least one set (10a, 10b, 10c, lOd) of thread segments (7) extending along a path (12a, 12b, 12c, 12d) , said at least one path (12a, 12b, 12c, 12d) being similar in shape to said at least one path (11a, lib, lie, lid) along which said at least one set (9a, 9b, 9c, 9d) of gaps (8) extend, but rotated around the center axis (13) of the closure portion (5) .

5. A container (1) according to any of claims 2 to 4, characterized in that the length of said gaps (8) is larger than the length of said thread segments (7) , said lengths being the dimensions of said thread segments (7) and said gaps (8) along the helical path of said thread (3) .

6. A container (1) according to any of claims 1 to 5, characterized in that the outer side (6) of the closure portion (5) is smooth in an area extending from or nearly from the mouth (18) of the container (1) .

7. A container (1) according to any of claims 1 to 6, characterized in that the container is a plastic drinking bottle.

8. A cap (2) for a container (1) according to any of claims 1 to 7, comprising: a center portion (15) with an external thread (16) which matches the thread (3) of the inner side (4) of the closure portion (5) of said container (1) , first sealing means (17) to seal the contents of the container (1) , and a skirt (19) which covers the outer side (6) of the closure portion (5) of the container (1) , characterized in that said skirt (6) comprises: second sealing means (20) to seal the outer side (6) of the closure portion (5) of the container (1) from contaminants and/or microorganisms.

9. A cap (2) according to claim 8, characterized in that said second sealing means (20) comprises a flange (21) on the skirt (19) which forms a seal with a flange (22) on the closure portion (5) of the container (1) .

10.A cap (1) according to claim 8 or 9, characterized in that said center portion (15) is hollow (23) and is covered by a removable lid.

11.A method for manufacturing a container (1) according to claim 5 or 6 by means of an injection molding machine, said method comprising the steps of: - mounting on said machine, a form having a core (28,32) with at least one center part (29,33) and at least one retractable part (30,34), injecting melted plastic into the form, cooling the plastic below the solidification point, retracting the at least one retractable part (30,34) of the core (28,32) relative to the center part (29,33) of the core (28,32), rotating the core (28,32) relative to the formed part (1) , said rotation being less than a full rotation of the core (28,32), and - withdrawing the core (28,32) from the formed part (1) along a path similar in shape to the path (11a, lib, lie, lid) along which the at least one set (9a, 9b, 9c, 9d) of gaps (8) extend.