Patent Description:
Glass bottles and containers for consumer products, such as beverages or other liquid food products, form and the ecologic alternative to lightweight plastic containers and bottles. However, bottles and containers made of glass bear the risk to splinter, if the glass container falls on the ground. Hence, shards of a fallen glass container may cause injuries. Furthermore, glass bottles may function as returnable bottles. However, in use, the glass bottles are prone to scuffing which means, that the softer surface areas of the glass bottles are scratched, so that the optical appearance of the glass bottle becomes less attractive from refilling cycle to refilling cycle.

On the other side, an increase of the used material for the glass containers in order to increase the resistance of a respective glass container causes an increase of weight of the glass container which leads to an uncomfortable weight for the consumer.

<CIT> discloses a glass container comprising a wall section and a bottom section, wherein the wall section and the bottom section surround an inner volume, wherein the tempered section forms a sandwich structure comprising an outer compression stress layer and an inner tensile stress layer.

Hence, there may be a need to provide a glass container which is simple and cost-efficient to manufacture and comprises at the same time an increased resistance against failure from impact and internal pressure.

This need may be met by a glass container and a respective method for manufacturing a glass container according to the independent claims.

According to first aspect of the present invention, a glass container is presented. The glass container comprises a wall section and a bottom section, wherein wall section and the bottom section surround an inner volume. The tempered section forms a sandwich structure comprising an outer compression stress layer and an inner tensile stress layer. The bottom section comprises a bottom tempered section, wherein a thickness relation between the wall thickness of the wall tempered section and the bottom thickness of the bottom tempered section is between <NUM> and <NUM>,<NUM>. Hence, good results with respect to the robustness of the tempered section by providing a bottom thickness having the above-mentioned ranges.

According to further aspect of the present invention, a method for manufacturing a glass container as described above. The method comprises the steps of providing a glass container with a wall section and a bottom section, wherein the wall section and the bottom section surround an inner volume, and forming a tempered section at least in the wall section by thermal treatment, so that the tempered section forms a sandwich structure comprising an outer compression stress layer and an inner tensile stress layer. The bottom section comprises a bottom tempered section, wherein a thickness relation between the wall thickness of the wall tempered section and the bottom thickness of the bottom tempered section is between <NUM> and <NUM>,<NUM>. Hence, good results with respect to the robustness of the tempered section by providing a bottom thickness having the above-mentioned ranges.

The glass container according to the present invention may describe glass bottles or other glass packages for liquid or solid material, such as beverages or other disclose or solid food articles. The glass container is made of the respective wall section and a bottom section which surround the respective inner volume for storing the material restored. Additionally, the glass container may comprise an opening for filling the container. The glass container may comprise a bottleneck in which the opening is formed.

At least the wall section comprises the tempered section. Specifically, the complete wall section forms the tempered section. In a further exemplary embodiment, the wall section and the bottom section forms the tempered section. However, in alternative embodiments, only a section of the wall section is tempered. Hence, the tempered section is harder than surrounding glass sections. The tempered section of the glass bottle comprises a glass section which is treated in a tempering process for increasing the resistance of the glass material and the tempered section, respectively.

In an exemplary embodiment of the method, the tempering process comprises a heating of the tempered section to a temperature of <NUM> to <NUM> and a subsequently rapid cooling to a temperature of approximately <NUM> to <NUM> within a cooling duration of <NUM> minute to <NUM> minutes. For cooling the glass containers, ambient air may be blown into the inner volume and around the glass containers in order to provide a continuous cooling between the inner surface and outer surface of the glass container. According to an exemplary embodiment of the method the cooling is provided by blowing pressurized air with a temperature of <NUM> to <NUM> inside the glass container and from outside against the glass container. As a result, the tempered glass section is hardened and in particular harder than other glass sections which are not treated in the hardening process.

Specifically, by the present approach of the present invention it has found out, by controlling the cooling of the inner and outer surface of the tempered section, specific layers having different pre-stressed characteristics can be generated. Specifically, in the tempered section, and in the layer facing to the inner volume may be prestressed by tensile stress and may form the inner tensile stress layer and an outer layer facing to the environment of the tempered section may be prestressed by a compression stress and may form the outer compression stress layer. However, the interaction between the outer compression stress layer and the inner tensile stress layer forms a robust sandwich structure similar to a composite material.

According to a further exemplary embodiment at least the wall section comprises a tempered section having a wall thickness between <NUM>,<NUM> and <NUM>,<NUM>. During the tempering process a high inner stress of the glass material occurs such that many glass containers may have cracks and other defects due to the high internal tensions caused by the tempering process. Specifically, due to the difficult control of the cooling rate inside the inner side of the glass container and the outer side of the glass container, internal tensions are generated which may cause cracks. Hence, if providing a wall thickness that is too thick, the center sections of the wall element receive less cooling energy than the outer sections of the wall element, such that cracks are generated during the cooling period. On the other side, if the wall thickness of the glass container is too small, the glass containers are less robust specifically during handling of the glass between the heating process and the cooling process, so that the glass containers during the heat treatment may be damaged.

Hence, it has found out, that by providing for the tempered section with a wall thickness between <NUM>,<NUM> and <NUM>,<NUM>, in particular between <NUM>,<NUM> and <NUM>,<NUM>, the internal stress of the glass bottle during cooling is reduced so that a tempered section can be provided having less inner defects and at the same time providing proper resistance against mechanical damage.

According to a further exemplary embodiment a first wall thickness and a opposite second wall thickness of the tempered section at a predefined distance to the bottom section comprises a relation of <NUM>:<NUM>, in particular <NUM>:<NUM>,<NUM>. Specifically, the wall section forms a hollow cylinder which is closed by the bottom section on one side. An exemplary embodiment, the bottom section may form a cylindrical, rectangle or polygonal of the cylindrical wall section. However, based on the manufacturing process, the wall thickness of a first wall section at a certain distance to the bottom section may differ to the wall thickness of a second wall section being located at the same distance to the bottom section. However, it has found out, that if the thickness difference between two (opposing) wall sections having the same distance to the bottom surface is too much, defects procure during heating and cooling the glass container, even if the wall thickness of the wall section is within the above-described inventive range. However, it has found out, that if the thickness relation between first wall thickness and the opposite second wall thickness of the tempered section at a predefined distance to the bottom section is within the above defined relation, less stress and defects are generated and a good hardening result is achieved.

According to a further exemplary embodiment, the outer compression stress layer has a wall thickness of <NUM> to <NUM>, in particular <NUM> to <NUM>. Additionally or alternatively, the inner tensile stress layer has a wall thickness of <NUM> to <NUM>, in particular <NUM> to <NUM>. Specifically, the thickness of the specific layers can be adjusted by respective cooling power applied to the inner side or the other side of the glass container during tempering. It has found out, that by providing the inner tensile stress layer thicker, in particular by the above-mentioned values, with respect to the thinner outer compression stress layer, a robust sandwich and tempered section, respectively, can be achieved.

According to a further exemplary embodiment, the outer compression stress layer comprises a pretensioned compression stress of -<NUM> MPa to -<NUM> MPa, in particular -<NUM> to -<NUM> MPa, more in particular -<NUM> MPa to -<NUM> MPa. Additionally or alternatively, the inner tensile stress layer comprises a pretensioned tensile stress of <NUM> MPa to <NUM> MPa, in particular <NUM> to <NUM> MPa more in particular <NUM> MPa to <NUM> MPa. It has found out during tests, in particular internal pressure tests and impact tests, that by providing the tensile stress in the inner tensile stress layer and the compression stress in the compression stress layer within the above-mentioned ranges, a most robust sandwich and tempered section, respectively, can be achieved.

The values for the tensile stress and the compression stress define the maximum stress values within a respective layer. Specifically, the compression stress of a compression layer reduces in the direction to the tension layer and vice versa. At a transition section between a compression stress layer and a tensile stress layer, the value for the stress is <NUM>.

According to a further exemplary embodiment, wherein the sandwich structure further comprises an inner compression stress layer, wherein the inner tensile stress layer is arranged between the outer compression stress layer and the inner compression stress layer. Specifically, by controlling the cooling of the inner and outer surface of the tempered section, the above-mentioned central structure can be generated, specifically a sandwich structure having the central inner compression stress layer covered by the outer and inner tensile stress layer. Specifically, it has found out, that the inner tensile stress layer is prone to external impacts. Hence, by additionally providing the in the compression stress layer, the central tensile stress layer is fully covered and protected by the surrounding compression stress layers. The inner compression stress layer faces the inner volume and is in particular in contact with the inner volume of the glass container. Hence, the interaction between the outer compression stress layer, the inner tensile stress layer and the inner compression stress layer forms a robust sandwich structure.

According to a further exemplary embodiment, the inner compression stress layer has a wall thickness of <NUM> to <NUM>, in particular <NUM> to <NUM> and wherein the inner compression stress layer comprises a pretensioned compression stress of -<NUM> MPa to -<NUM> MPa, in particular -<NUM> to -<NUM> MPa, more in particular -<NUM> MPa to -<NUM> MPa. Specifically, the thickness of the specific layers can be adjusted by respective cooling power applied to the inner side or the other side of the glass container during tempering. It has found out, that by providing the inner compression stress layer thinner than the outer compression stress layer according to the ranges as described above, a good robustness against impacts can be achieved. Specifically, it has found out, that by providing the inner tension stress layer thicker than the outer and the inner compression stress layer, a robust sandwich and tempered section, respectively, can be achieved.

According to a further exemplary embodiment, the bottom section comprises a bottom thickness between <NUM> and <NUM>, in particular <NUM>,<NUM> to <NUM>. Specifically, the thickness of the bottom section interacts as well with the tempered section since due to the cooling speed of the glass container during tempering, respective stress in the temper section affected by the thickness of the bottom section can appear. Hence, good results with respect to the robustness of the tempered section have been found by providing a bottom thickness having the above-mentioned ranges.

According to a further exemplary embodiment, a thickness relation between the wall thickness of the wall tempered section and the bottom thickness of the bottom tempered section is between <NUM>,<NUM> and <NUM>,<NUM>. Hence, good results with respect to the robustness of the tempered section by providing a bottom thickness having the above-mentioned ranges.

According to a further exemplary embodiment, the bottom tempered section forms a bottom sandwich structure comprising a bottom outer compression stress layer and a bottom inner tensile stress layer. The bottom outer compression stress layer has a wall thickness of <NUM> to <NUM>, in particular <NUM> to <NUM>. Additionally or alternatively, the bottom inner tensile stress layer has a wall thickness of <NUM> to <NUM>, in particular <NUM> to <NUM>. Additionally or alternatively the bottom outer compression stress layer comprises a pretensioned compression stress of -<NUM> MPa to -<NUM> MPa, in particular -<NUM> to -<NUM> MPa, more in particular -<NUM> MPa to -<NUM> MPa. Additionally or alternatively the bottom inner tensile stress layer comprises a pretensioned tensile stress of <NUM> MPa to <NUM> MPa, in particular <NUM> MPa to <NUM> MPa more in particular <NUM> MPa to <NUM> MPa. The thickness of the specific layers can be adjusted by respective cooling power applied to the inner side or the other side of the glass container during tempering. Furthermore, the cooling rate of the bottom sandwich structure may be controlled by a temperature-controlled cooling plate to which the glass container may be adjusted during tempering. Specifically, by applying one of the above-mentioned parameters for the bottom structure, good results with respect to the robustness of the tempered section and the bottom sandwich can be achieved.

According to a further exemplary embodiment, the bottom sandwich structure further comprises a bottom inner compression stress layer, the inner tensile stress layer is arranged between the outer compression stress layer and the inner compression stress layer, wherein the bottom inner compression stress layer has a bottom wall thickness of <NUM> to <NUM>, in particular <NUM> to <NUM> wherein the bottom inner compression stress layer comprises a pretensioned compression stress of -<NUM> MPa to -<NUM> MPa, in particular -<NUM> to -<NUM> MPa, more in particular -<NUM> MPa to -<NUM> MPa. It has found out, that by providing the bottom inner compression stress layer thinner than the bottom outer compression stress layer according to the ranges as described above, a good robustness against impacts can be achieved. Specifically, it has found out, that by providing the bottom inner tension stress layer thicker than the bottom outer and the inner compression stress layer, a robust sandwich and tempered section, respectively, can be achieved.

According to a further exemplary embodiment, the glass container further comprises a bottleneck section comprising an opening between the environment and the inner volume. The walls section is formed between the bottom section and the bottleneck section, wherein the bottleneck section comprises a bottom tempered section forming a bottleneck sandwich structure comprising a bottleneck outer compression stress layer and a bottleneck inner tensile stress layer. The bottleneck sandwich structure further comprises in particular a bottleneck inner compression stress layer. The thickness of the bottleneck section interacts as well with the tempered section since due to the cooling speed of the glass container during tempering, respective stress in the temper section affected by the thickness and the structure of the bottleneck section can appear. Hence, good results with respect to the robustness of the tempered section have been found by providing also a bottleneck sandwich structure as described above.

According to a further exemplary embodiment, wherein the material of the glass container comprises more than at least <NUM>%, in particular more than <NUM> %, sodium carbonate. By adding sodium carbonate, the melting point of the raw glass material is reduced so it can be transformed into glass at lower temperatures. It has found out that by providing the above-described sodium carbonate concentration, an proper tempering process can be provided, since lower start temperatures and hence a respectively adapted cooling rate during tempering has a positive effect on the robustness of the tempered glass containers.

Summarizing, by the approach of the present invention a glass container is provided having a higher robustness and a higher durability. Furthermore, improved abrasion and scratch resistance (scuffing) is provided. As an additional effect, due to the more robust glass container, less material may be used so that an up to <NUM>% lighter glass container can be provided (especially for returnable bottles). The tempered glass container with the respective thicknesses and in particular with the sandwich structure according to the present invention, an improved internal pressure resistance, improved impact resistance, improved thermal shock resistance is provided. Furthermore, it has shown than high resistance and an improved drop test performance in drop tests of glass containers from a height of <NUM> to <NUM> meters are achieved by the presented glass containers. Furthermore, by the described glass container, shards of broken glass containers according to the present invention are not too small and thus visible and easy to clean from the ground for the consumer.

Also for the bottlers of the described glass containers benefits are provided. Specifically filling line performance due to less breakages can be enhanced, and an easier packaging is possible, since e.g. no cardboard box dividers are necessary. Furthermore, the weight reduction of returnable and non-returnable packaging glass at higher strength is possible. Additionally, specifically due to the soda concentration and the possible material reduction, a carbon footprint reduction is possible.

It has to be noted that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments have been described with reference to apparatus type claims whereas other embodiments have been described with reference to method type claims.

It is noted that in different figures similar or identical elements are provided with the same reference signs.

<FIG> shows a schematical view of a glass container <NUM> according to an exemplary embodiment of the present invention. The glass container <NUM> comprises wall section <NUM> and a bottom section <NUM>, wherein the wall section <NUM> and the bottom section <NUM> surround an inner volume Vi, wherein the tempered section <NUM> may also form a sandwich structure <NUM> comprising an outer compression stress layer <NUM> and an inner tensile stress layer <NUM> as shown in detail in <FIG>. Furthermore, the wall section <NUM> comprises a tempered section <NUM> having a wall thickness tw between <NUM>,<NUM> and <NUM>,<NUM>.

The glass container <NUM> describes in the shown embodiment a glass bottle for liquid or solid material, such as beverages or other disclose or solid food articles. Additionally, the glass container <NUM> comprises a bottleneck section <NUM> having an opening for filling the container <NUM>.

At least the wall section <NUM> comprises the tempered section <NUM>. Specifically, the complete wall <NUM> section forms the tempered section <NUM>. By the exemplary embodiment, the tempered section <NUM> has a wall thickness between <NUM>,<NUM> and <NUM>,<NUM>. Hence, the internal stress of the glass container <NUM> during cooling is reduced so that a tempered section <NUM> can be provided having less inner defects and at the same time providing proper impact resistance.

A first wall thickness tw1 and an opposite second wall thickness tw2 of the tempered section <NUM> at a predefined distance to the bottom section comprises a relation of <NUM>:<NUM>. Specifically, in the present example, the wall section <NUM> forms a hollow cylinder which is close by the bottom section <NUM>. The bottom section <NUM> may form a cylindrical, rectangle or polygonal base/ground area of the cylindrical wall section <NUM>. The wall thickness tw1 of a first wall section at a certain distance to the bottom section <NUM> differs to the wall thickness tw2 of a second wall section being located at the same distance to the bottom section <NUM>.

The bottom section <NUM> comprises as well a bottom tempered section, wherein a thickness relation between the wall thickness tw1, tw2 of the wall tempered section <NUM> and the bottom thickness tB of the bottom tempered section is between <NUM> and <NUM>,<NUM>.

The bottom section <NUM> comprises a bottom thickness tb between <NUM> and <NUM>. Specifically, the thickness tb of the bottom section <NUM> interacts as well with the tempered section <NUM> since due to the cooling speed of the glass container <NUM> during tempering, respective stress in the temper section <NUM> affected by the thickness of the bottom section <NUM> can appear.

The material of the glass container <NUM> comprises more than at least <NUM>%, in particular more than <NUM> %, sodium carbonate.

<FIG>shows a schematic overview a sandwich structure of a glass container <NUM> according to an exemplary embodiment of the present invention. The tempered section <NUM> forms a sandwich structure <NUM> comprising an outer compression stress layer <NUM> and an inner tensile stress layer <NUM>. Specifically, by controlling the cooling of the inner and outer surface of the tempered section <NUM>, specific layers <NUM>, <NUM>, <NUM> having different pre-stressed characteristics can be generated.

The sandwich structure comprises an inner compression stress layer <NUM>, wherein the inner tensile stress layer <NUM> is arranged between the outer compression stress layer <NUM> and the inner compression stress layer <NUM>. Specifically, by controlling the cooling of the inner and outer surface of the tempered section <NUM>, the shown structure can be generated, specifically a sandwich structure <NUM> having the central inner compression stress layer <NUM> covered by the outer and inner tensile stress layer <NUM>, <NUM>. By additionally providing the in the compression stress layers <NUM>, <NUM>, the central tensile stress layer <NUM> is fully covered and protected by the surrounding compression stress layers <NUM>, <NUM>. The inner compression stress layer <NUM> faces the inner volume Vi and is in particular in contact with the inner volume Vi of the glass container. Hence, the interaction between the outer compression stress layer <NUM>, the inner tensile stress layer <NUM> and the inner compression stress layer <NUM> forms a robust sandwich structure <NUM>.

The outer compression stress layer <NUM> has a wall thickness to of <NUM> to <NUM>. The inner tensile stress layer <NUM> has a wall thickness tm of <NUM> to <NUM>. The inner compression stress layer <NUM> has a wall thickness ti of <NUM> to <NUM>. Specifically, the thickness of the specific layers <NUM>, <NUM>, <NUM> can be adjusted by respective cooling power applied to the inner side or the other side of the glass container <NUM> during tempering. It has found out, that by providing the inner tensile stress layer <NUM> thicker, in particular by the above-mentioned values, with respect to the thinner outer compression stress layers <NUM>, <NUM>, a robust sandwich <NUM> and tempered section <NUM>, respectively, can be achieved.

The bottom section <NUM> may also form a bottom sandwich structure comprising a bottom outer compression stress layer and a bottom inner tensile stress layer similar as shown in <FIG>. The bottom outer compression stress layer has a wall thickness of <NUM> to <NUM>, a bottom inner tensile stress layer has a wall thickness of <NUM> to <NUM> and a bottom inner compression stress layer has a bottom wall thickness of <NUM> to <NUM>.

<FIG> illustrates a diagram of respective pretensioned compressing layers <NUM>, <NUM> and a tension layer <NUM> according to an exemplary embodiment of the present invention. Along the x-axis, the way from the outer surface through the tempered section <NUM> along the thickness direction of the wall thickness tw to the inner surface facing the inner volume Vi is shown. The wall thickness is defined at a location where the smallest thickness of the wall section is existent. The y-axis describes the measured pretensioned stress level of the layers <NUM>, <NUM>, <NUM>, wherein the tensile stress has a positive sign and the compression stress has a negative sign.

In the shown exemplary embodiment the outer compression stress layer <NUM> comprises a maximum pretensioned compression stress -<NUM> MPa. The inner tensile stress layer <NUM> comprises a maximum pretensioned tensile stress of <NUM> MPa. The inner compression stress layer <NUM> comprises a maximum pretensioned compression stress of -<NUM> MPa. The maximum compression stress of the outer compression stress layer <NUM> and inner compression stress layer <NUM> as formed at the outer surfaces of the tempered section <NUM>. The maximum tensile stress of the inner compression stress layer <NUM> is formed in the center (regarding the thickness of the tempered section <NUM>) of the inner tensile stress layer <NUM>. The values for the tensile stress and the compression stress define the maximum stress values within a respective layer. Specifically, the compression stress of a compression stress layers <NUM>, <NUM> reduces in the direction to the inner tensile stress layer <NUM> and vice versa. At a transition section between a compression stress layers <NUM>, <NUM> and a tensile stress layer <NUM>, the value for the pretensioned stress is <NUM>.

It has found out during tests, in particular internal pressure tests and impact tests, that by providing the tensile stress in the inner tensile stress layer and the compression stress in the compression stress layer within the above-mentioned ranges, a most robust sandwich and tempered section, respectively, can be achieved.

Claim 1:
Glass container (<NUM>), comprising
a wall section (<NUM>) and a bottom section (<NUM>),
wherein the wall section (<NUM>) and the bottom section (<NUM>) surround an inner volume (Vi),
wherein the tempered section (<NUM>) forms a sandwich structure (<NUM>) comprising an outer compression stress layer (<NUM>) and an inner tensile stress layer (<NUM>),
wherein the bottom section (<NUM>) comprises a bottom tempered section,
wherein a thickness relation between the wall thickness (tw) of the wall tempered section (<NUM>) and the bottom thickness of the bottom tempered section is between <NUM> and <NUM>,<NUM>.