BRETON, Donald Victor (174 Cemetery Street, North Vassalboro Maine, Maine, 04962, US)
SHARMA, Mangat Rai (Lemvig Veien 17, Jevnakar, NO-3520, NO)
BRETON, Donald Victor (174 Cemetery Street, North Vassalboro Maine, Maine, 04962, US)
| Claims 1. A moulded fiber lid for a container with a container wall with a circumferential rim which has an upper surface and which extends from said container wall, said lid comprises a circumferential, curved locking wall which in contact follows said rim of said container in a radial direction starting from below said upper surface over at least 110 degrees and which lid comprises at least one solid notch extending from said curved locking wall at a position in radial direction remote from said starting position and which notch is provided for snappingly attaching said lid on said rim of said container. 2. The moulded fiber lid of claim 1, wherein said at least one solid notch comprise at least two circumferentially spaced apart solid notches or a substantially circumferential solid notch. 3. The moulded fiber lid of any one of the preceding claims, wherein a density of said notch or notches is lower than the density of said further lid. 4. The moulded fiber lid of any one of the preceding claims, wherein said lid is made from hot-pressed moulded fibre material. 5. The moulded fiber lid of any one of the preceding claims, wherein said rim of said container extends outward, in particular in a rolled rim, and said curved locking wall is curved in radial direction following said rim over at least 110 degrees, in particular over at least 120 degrees. 6. The moulded fiber lid of any one of the preceding claims, wherein said lid is substantially round or elliptic. 7. The moulded fiber lid of any one of the preceding claims, comprising a top wall and a circumferential wall extending from said top wall and continuing in said curved locking wall. 8. The lid according to one of the preceding claims, wherein said lid is produced using a smooth moulded fibre moulding method, said method comprising the steps of suction moulding at least one lid to provide a wet moulded lid, bringing said wet moulded lid on a vacuum mould and hot-pressing said wet moulded lid. 9. The lid according to one of the preceding claims, wherein edges of the lid are treated with a polymer solution for avoiding free fibre ends coming off of the edges. 10. The lid according to one of the preceding claims, wherein said locking wall comprises several, in an embodiment at least four, notches, in an embodiment said notched are solid notched. 11. The lid according to one of the preceding claims, wherein said notches have a small negative draft angle providing an undercut. 12. The lid according to one of the preceding claims, wherein said notches are circumferentially spaced apart. 13. The lid according to one of the preceding claims, wherein said notches extend about 0.05-0.5 mm from an inner surface of said curved locking wall, in an embodiment about 0.2-0.35 mm from said inner surface. 14. A container assembly comprising the container part and said lid according to the preceding claims. 15. Method for producing a lid according to claims 1 to 13, comprising the steps of suction moulding at least one lid producing a wet moulded lid, bringing said wet moulded lid on a vacuum mould and hot-pressing said wet moulded lid. -o-o-o-o-o-o- |
The present invention relates to a moulded fiber lid for a container, such as a disposable cup, for instance a milkshake cup, soft drink beverage cup, disposable coffee cup, or the like. A lid which can be snapped on a such a cup or a beaker are well known. The cup usually has a rim from an outwardly rolled back upper part of the cup, also referred to as a rolled rim. Usually, the lids are injection moulded of thermo formed from all sorts of plastic material. A disadvantage of this material is that these lids cause a lot of waste, and end up as litter in the natural environment. Plastics decompose only very slowly in this natural environment. The plastic litter therefore remains a burden on the environment for a long time. Furthermore, they often require the use of precious sources of raw material.
These lid are thus used for containers for consumable products, such as food or beverages.
Convenience food and beverage chains typically dispense hot beverages such as coffee, tea or soup, or cold beverages such as carbonated drinks, via disposable containers. These may, for example, be made of low-cost paper, card board or plastics material. Disposable lids for the containers are also frequently provided and can assist in reducing the risk of spillage, or in keeping a beverage hot (or cold) for an extended period of time. These factors are particularly important if a consumer is likely to take a beverage on a journey e.g. by rail, road, air or by foot. Also for ice cream and for instance milkshakes, these disposable containers are often used. For instance WO- 2010/027365 discloses such a paper cup with a plastic lid.
Lids for such disposable containers are generally circular or elliptic in shape and frequently provided with an annular recess designed for receiving a complementarily shaped rim. Press fitting of the rim into the recess can then be used to provide a good seal until the lid is removed (e.g. when it was desired to drink the beverage or eat the ice cream). An even tighter seal is desired when the lid should stay on the cup during drinking, like for instance for so called sip lids.
An additional frequently encountered problem is that, in order to keep down costs, walls of the lids are often made of thin plastic material. Furthermore, these lids tend to lack stiffness. A lid of the present invention can be used for a container to contain any desired substance and is not limited to containing particular foods or beverages. It is however particularly useful in containing hot or cold foods or beverages - e.g. chilled drinks, icecream, milk shakes, tea, coffee, hot chocolate, soup, etc. The container can be any desired shape. For example, it may be frustroconical.
Typically, packaging is a low margin product and should be produced in a manner that is amenable for high speed production and not result in any appreciable increase in the cost of the container to the food manufacturer. This is even more so for disposable containers. Because packaging equipment is expensive, it is often times been found desirable to manufacture container components at one facility and assemble them at another facility after filling. It is also desired that the final assembly of the filled containers be done with currently existing machinery at the food production plant. This eliminates the need for a new machine at each manufacturing facility and the attendant costs.
US-2006 213916 discloses a moulded fibre container lid having a skirt extending around the perimeter and having an inside surface into which an undercut is made. The lid is designed to fit onto a base container. The lid is wet-pressed from fibre pulp and subsequently dried. This provides relatively thick, rough products. The lid in fact has a thickened circumferential rim in the skirt locking the lid onto a base container.
Placement and removal leave room for improvement. Furthermore, leak-tightness can be improved. GB- 1.163.740 discloses a closure for containers like mustard jars which should provide a perfectly hermetic seal coupled with mechanical strength. The cover is stamped from metal alloy and has a sealing member of rubber in a peripheral annular part. Such a lid is applied onto a container using a pressure tool which changes the shape of an outer edge portion of the lid by increasing its diameter in order to deform the sealing member to provide fluid-tightness. The lid is held in position by the radial pressure of sealing member and may be supported by a resilient edge which is stamped in the metal. Such a lid is used for storing condiments or other products. Such a lid clearly is not the type of lid for temporarily closing a drinking cup of the like. It is not easy and cheap to produce, is made from metal or the like, and a tool is used to apply it on a container.
Summary of the Invention The invention aims to improve current disposable containers.
In particular, the invention seeks to provide a disposable lid for such a container, in particular a snap-on lid which is easy to apply or snap on the rim of a container.
Furthermore, a substantially leak-tight lid is provided.
According to a first aspect of the invention this is realized with a moulded fiber lid for a container with a container wall with a circumferential rim which has an upper surface and which extends from said container wall, said lid comprises a circumferential, curved locking wall which in contact follows said rim of said container in a radial direction starting from below said upper surface over at least 110 degrees and which lid comprises at least one solid notch extending from said curved locking wall at a position in radial direction remote from said starting position and which notch is provided for snappingly attaching said lid on said rim of said container. It was found that when providing such a lid from moulded fiber material makes it possible to provide a lid which has many beneficial qualities. Moulded fiber material is not a first material one thinks of when designing lids. It was found that it is possible to make it look attractive. It is cheap and fast to produce. It was found to have a good carbon footprint. It was found to be stiff enough to provide a proper lid which can be pushed onto a container without being damaged, when designed carefully. Furthermore, it can be manipulated in an automated environment. And, finally, it was found to be biodegradable. This allows a lid which has seemingly contradictory properties which also seem to contradict the basic properties of moulded fiber. In contrast to plastic lids, it was found that it does not harm animals, for instance hedgehogs which tend to roam waste sites near fast food restaurants. The lid due to its wall part fitting onto the rim provides a leak-tight fit and, despite the material properties which at first seem unbeneficial, also a secure fit. In particular, it allows the lid to be fit using a vertical application load of about 50-70 N, in particular 55-65 N when fitting the lid onto a drinking cup like a (disposable) coffee cup or milkshake cup, for instance. This can provide a slightly higher retention load of the lid onto the rim of the container. In practice, the retention load can be about 55-75 N, in particular about 59-70 N.
Furthermore, The material and the shape of the locking wall were found to contribute in the leak-tight fitting of the locking wall on the rim.
As described above, food containers with removable lids are well known in the industry. Such containers will typically comprise a container bottom or receptacle having a cavity therein for the storage of a food product. The container receptacle will typically have a sidewall, a bottom wall and an upwardly opening top defined by a peripheral lip. A lid is removably mounted or snapped to the receptacle at the open end to selectively close the container opening. The lid may be semi-permanently secured to the receptacle or may be easily removably mounted to the receptacle as for example a friction fit or held in place by a snap lock fit. For some food products, a membrane closure can also be provided for hermetically sealing the container bottom and to provide tamper evidence should the container be opened prior to sale or even after sale. Such containers may be sold as singles or in a multi-pack version. An overwrap may also be provided for the container, particularly those containers which have the lid easily removable, to help prevent tampering and accidental lid removal. Containers with easily removable lids can be used for ice cream, yogurt, margarine, sour cream, dips, sauces and the like. In such case, the container bottom or receptacle is made from a material and by a method compatible with the product to be stored. Examples of such receptacles include a helically wrapped paperboard, a side seamed wrapped construction, a polymeric container made by injection moulding, thermo forming or vacuum forming. After use, the container together with the lid is disposed.
The lid or cover thus includes a notch extending inwardly from the outer periphery of the flange to allow a consumer to easily remove it. In particular, it was found that it was possible to provide at least two solid notches, or a single substantially circumferential notch. These notches are solid, but have a density below the density of the lid. This makes the notch or notches a little flexible and elastically compressible, despite the choice of material. The notch or notches are extending in a radially inward direction, thus being so called undercut notch or notches. The present invention also involves the provision of a process for manufacturing a food container including a lid and container bottom. The container bottom is suitably formed.
In some cases, the container is filled with product, for instance ice cream, at a point of sales, and subsequently the lid is placed on the rim of the container. In such case, the lid should be stiff enough to properly place it on the filled container, and the snap-lock should be fail safe but sure. In fact, the current construction in combination with the used moulded fiber technique allows a lid which is extremely stiff and strong. In an embodiment, the container is a cup. In an embodiment, the upper rim of said cup extends outward. It can have an outward flared rim. Said outward flared rim can even continue into a rolled rim which is common for paper cups. Usually the rim is rolled outward, but thus is not required. In another embodiment, the rim is thickened. A rim extending outward from the wall of the cup provides the easiest basis for snapping the lid onto the cup. The rim has an upper surface. The curved locking surface starts following, in radial direction, the rim from the inside of the cup below the upper surface and continues beyond the widest part of the rim. In combination with the notch or notches which is or are below this widest part this provides a snapping closure. Often, the container and lid are circular of elliptic.
A further aspect of the lid is that it allows efficient stacking and de-stacking because of its smooth- finish production from fiber pulp. In an embodiment, said at least one solid notch comprise at least two circumferentially spaced apart solid notches or a substantially circumferential solid notch.
In an embodiemnt, a density of said notch or notches is lower than the density of said further lid.
In an embodiment, said rim of said container extends outward, in particular in a rolled rim, and said curved locking wall is curved in radial direction following said rim over at least 110 degrees, in particular over at least 120 degrees. In a particular embodiment, said notch or notches are in radial direction about 120-200 degrees away from said starting point where said curved locking lid starts following said rim. Near said notch, the curved locking surface may not be in contact with said rim. In an embodiment, said notch is pased the widest part of said rim for better snapping. The notch or notches may be 170-200 degrees away from said starting point. Thus, the curved locking wall can grap said rim.
In an embodiment, said lid is substantially round or elliptic. Thus a better closure may be possible. In an embodiment, the moulded fiber lid comprises a top wall and a circumferential wall extending from said top wall and continuing in said curved locking wall.
In an embodiment, said lid is produced using a smooth moulded fibre moulding method, said method comprising the steps of suction moulding at least one lid to provide a wet moulded lid, bringing said wet moulded lid on a vacuum mould and hot- pressing said wet moulded lid. In particular, the moulded fiber materil or said lid surface may be probided with a wax additive or wax coating layer for improving water resistance. A skilled person will recognize further, equivalent compounds. In an embodiment, the pulp is processed in a moulded fiber technology using high grade post industrial fiber qualities. In an embodiment, unprinted scan board cuttings and/or mixtures with virgin fiber qualities are used. In fact, cellulose fiber material is used which is suitable for direct food contact according to BfR compliance, German recommendation XXXVI for health related evaluation of materials and objects for direct contact compliance with the foodstuffs.
In an embodiment, the lid comprises a top wall and a circumferential wall extending downwardly from said top wall. Said circumferential wall may continue in a flange, said flange comprising a circumferential wall part extending outwardly from said circumferential wall for resting on an upper rim of said container and a circumferential locking wall extending downwardly from said wall part for encircling the upper rim of said container. In an embodiment, said locking wall comprises at least two solid notches of a substantially circumferential notch for snappingly attaching said lid around said upper rim of said container.
In an embodiment, said circumferential wall is substantially conical. In a further or alternative embodiment, said circumferential wall is curved inwardly.
In an embodiment, said circumferential wall comprises substantially conical buttresses. These rounded, outward extending parts provide additional strength, on particular when pushing the lid onto a container. In an embodiment, said flange further comprises a circumferential rim extending outwardly from said locking wall.
In an embodiment, said lid is produced using a smooth moulded fibre moulding process, said process comprising the steps of suction moulding at least one lid producing a wet moulded lid, bringing said wet moulded lid on a vacuum mould and hot-pressing said wet moulded lid.
In an embodiment, said locking wall comprises several, in an embodiment at least four, notches, in an embodiment said notched are solid notched. These notches can be positioned around the circumference. In moulded fiber, it was found that such an embodiment makes it possible to on the one hand produce these lids in mass production, and on the other hand provide a sufficient snap fit to a cup or beaker. In an embodiment, said notches have a small negative draft angle providing an undercut. In this way, which is not evident in moulded fiber technology as it complicates removal from a mould, it allows the lid to snap onto the rim of a container. In an embodiment, said notches are circumferentially spaced apart.
In an embodiment, said substantially circumferential notch of said notches extend about 0.05-0.5 mm from an inner surface of said locking wall, in an embodiment about 0.2- 0.4 mm from said inner surface. It was found that these sizes still allow removal from a mould, but also allow sufficiently firm snapping on the rim of a container.
The invention further pertains to a container comprising a container part having a bottom wall and a circumferential sidewall connected to said bottom wall and having an upper rim, and the lid described above snap fitted on said rim.
In an embodiment, the lids were made using the smooth moulded fiber technology, but it is possible to manufacture lids using the rough moulded fiber technology in combination with after pressing. When using molded fiber technology, it is possible to produce lids that are made of renewable/sustainable materials which have been proven to comply with
EN13432:2000 (compo stability and biodegradability). In fact, when additionally using containers from a biomaterial coated paper, for instance, it is possible to provide a container, in particular for food products, in particular of the disposable type, that is fully biodegradable and compostable together and does not have to be collected in the waste bin
In an embodiment, the snap fitting allows the lid to be pushed onto the cup or beaker. It may use at least three, but preferably four or more different spots/under- cuts provided by a locally thickened part. At these thickened spots it is possible to make a small negative draft angle which is unique for snap on lid application and normally not possible in moulded fiber. Number of under-cuts may be increased to five or six or more depending on the diameter of the cup and requirement of how tight fit it should provide. Accordingly, it is possible to produce a moulded fiber lid which provides a leak-tight container.
In an embodiment, ASA or AKD sizing may be used to make the fiber lids more water resistant.
In an embodiment, a hole of a certain diameter can be punched, cut or trimmed to enable the use of e.g. a spoon to mix of stir the contents like ice or liquid content of the container. As the lid is made from moulded fiber material, the cut-out part can easily be reintroduced in the production process. Thus leading to zero waste.
The height of the lid dome can be adjusted according to the end use requirement. In some embodiments, the height is about 2-4 cm. In other embodiments, a flatter or higher lid may be provided.
In an embodiment, the lid has a wall thickness of about 0.4-0.8 mm. It was even found to be possible to produce a lid with a wall thickness of about 0.35-0.60 mm. These thicknesses were measured using the Tappi T411 standard method. Using the NEN- EN-ISO 543 2005 gives almost the same results in this case. For comparison reasons, an egg carton made of moulded fiber material has a wall thickness of about 0.88 mm or more.
In an embodiment, at least two notches are provided circumferentially spaced apart. Thus, they can hold the lid firmly on a container. Alternatively, a substantially circumferential notch is provided. In an embodiment, the notch or notches extend about 0.05-0.5 mm from the remaining surface of the circumferential locking flange wall. In an embodiment, the notches extend about 0.2-0.4 mm from said surface. It was found that even such a small extension provided sufficient gripping or allow sufficiently firm snapping on the rim of a container to hold the lid on a container. For instance enough gripping was provided for holding a so-called "sip lid" onto a beaker or cup. In an embodiment, cutting edges may be edge coated with a polymer solution. Thus, it may be avoided that loose fibers fall into the contents, like ice cream or liquid content, of the container. The invention further relates to an apparatus comprising one or more of the characterising features described in this description and/or shown in the attached drawings.
The invention further relates to a method comprising one or more of the characterising features described in this description and/or shown in the attached drawings.
The various aspects discussed in this patent can be combined in order to provide additional advantages. Some of the features may for part of a divisional application.
Description of the Drawings
The invention will be further elucidated referring to an embodiment of a moulded fiber lid shown in the attached drawings, showing in:
Figure 1 a perspective view of a lid;
Figure 2 a cross sectional side view of figure 1 ;
Figure 3 a view in the lids of figure 1 ;
Figure 4 the lid of figure 1 on a container;
Figure 5 a detail on a perspective view of a vacuum die wear ring;
Figure 6 a cross section through part of figure 5;
Figure 7 a radial cross section of a further embodiment of a lid on a container. Detailed Description of Embodiments
In figure 1 , a two lids 1 are shown. These lids are connected via a bridge part. In this example, two lids are produced in one moulding step, in practise it may be possible to produce several connected lids 1. In this embodiment, lid 1 is circular or round. Other shapes like elliptic may be possible. Most cup and bakers, however, are round.
The lids 1 comprise a top wall 2 and a circumferential wall 3 connected to the top wall 2. The circumferential wall 3 in this embodiment is substantially conical. Thus improves the strength. Furthermore, the circumferential wall 3 is slightly curved in inward direction. In combination with flange 4, it provides additional strength. The strength is even further increased by adding substantially conical buttresses 10 to the circumferential wall 3. These buttresses have a wall part and a smooth transition to the connecting wall parts. Together, they form the circumferential wall 3. It was found that the construction provided so much strength that it is possible to press hard on the top wall 2 and sill leave the lid intact.
Flange 4 has several functional parts. It comprises a circumferential flange wall part 5 which extends outward from circumferential wall 3 to allow the lid to rest on top of the rim of a container. It further comprises a circumferential locking flange 6. This locking flange runs from the flange wall part 5 down. Its perimeter is adapted to fit around a rim of a container. In order to provided additional stiffness, flange 4 further comprises an outward reaching flange rim 8. This flange rim 8 runs from locking flange 6 outward.
In order to allow the lid to be snapped onto a rim of a container, the locking flange 6 comprises several notches 7 at its inner perimeter or surface. These notches 7 are massive. In order to provide a better sealing of the container, they are provided with a negative draft angle. This means that an undercut is created. This, when properly adapted to the rim of a container, may allow a liquid-tight sealing. In most cases, the rim of the container is folded outward and sometimes even curved outward. The height of the notches 7 can be a little smaller than the height of the rim part, thus pulling the lid tightly on the container. The inner perimeter of the locking flange 6 with notches 7 is often chosen a little smaller than the outer perimeter of the container, thus providing a better sealing of locking. In production, the flange rim 8 will extend a little further than needed, and it may comprise a bridging part 9 connecting a lid 1 to a next lid. In fact, in a similar way several lids may be interconnected. After production, the lids can be separated by punching them out, decreasing the width of the flange rim 8. In order to avoid free fiber ends, the cut edge may be treated with a polymer solution, which as such is known in the art.
The top wall 2 may comprise a cut-out part 12, indicated with dotted lines in figure 3. This cut-out part and parts of the flange rim 8 can be returned in the pulp without causing waste.
Figure 4 shows a lid 1 on top of a container 20. The container has a circumferential container wall 20 with a rim 21 of the type well known in the art. Often, the container is of the disposable type often used for drinks, beverages, milkshakes, or ice-cream. The notches 7 described above snap around the rim as indicated. In figure 4, it seems as if the notches 7 are depressions which are visible from the outside. This is actually not the case. Notches 7 are solid notches. The outside wall is smooth, and the notches 7 extend inwardly and lock snappingly behind rim 21. The negative draft angle mentioned before means that in a downward direction, the notches 7 extend further from the surface of locking flange 6. Thus, notches 7 pull the lid 1 on the cup or beaker 20.
In an embodiment, the lid is produced using a pulp moulding process which is known as smooth moulding. In this process, a pulp slurry is produced which is suitable for moulding. The slurry is brought in a container from which it is moulded. To that end, one or more suction moulds are brought into the slurry container. Next, one or more lids are moulded. Slurry is sucked onto the suction moulds. These suction moulds are often of a gauze material. Fibres of the slurry are sucked onto the suction mould. The mould or moulds are subsequently rotated out of the slurry. The lid or lids produced on the moulds are then pressed onto hot vacuum moulds. After this, the suction moulds rotate back into the slurry for making one or more lids. On the vacuum mould, the wet products are pressed at a high pressure. The lid or lid dry to a product dryness of 95%, i.e., the water contents will be about 5% by weight or less. Using hot moulds and pressure, it is possible to obtain a smooth product. The dried product is subsequently blown off the vacuum moulds and stacked. It was found possible to produce a lid with a weight of less than 4.0 gr. In fact, a weight of less than 3.5 gram was found possible for the single lid shown in figure 1. In practise, the centre part of the top wall 2 can be removed before use (fig. 3) or, in case of a drinking cup lid, small parts of a drinking spout. When the lid is made of moulded fiber material, these removed parts do not lead to additional waste, but can be reused in the production process.
The notches 7 need some specific technique, as usually so called undercut regions or regions which have a negative draft angle were thought to be impossible to produce as they do not come off of the mould, or cause problems in high speed production processes. Especially for notches which are circumferentially spaced apart, this was thought to pose problems.
Making the notches was found possible in the following way. The die on which the pulp is to be pressed was provided with undercuts. When the vacuum die is inserted into the pulp, it collects about 1.9-2.1 mm of pulp on its surface. The pulp will also fill the undercut regions which will form the notches. Next, the pulp will be pressed. When pressing, water will evade through the gauze of the vacuum die. In this way, it was found that additional fibre material would collect in the undercuts. Next, the pre- pressed pulp layer is hot pressed, thus further drying the fibre material, while leaving the undercut space at least partly filled with fibre material. The fibre material in the undercut will be pressed a little less than the remaining lid. Thus, the material of the notches will be a little more compressible than the remaining lid. After pressing, it will be possible to remove the lid from the die with undercut, despite the fact that the lid in fact has a negative draft angle with respect to the die.
It may even be possible to produced so called 'sip lids' using the current lid design of the current invention. The known 'sip lids' are made of plastic and have a drinking spout near an edge of the lid. In such an embodiment, circumferential wall 3 usually is less high, i.e. mostly 5-15 mm. In an embodiment, it does not have the buttresses 10.
In figure 5, a vacuum die wear ring 30 is shown which can be used in the production of the hot-pressed, moulded fibre lid. The die ring corresponds to commonly used die rings, but in this embodiment undercuts 31 were machined in the rings which correspond to the locking flange 6 and flange rim 8. In production, it was found that first the vacuum die collects about 2 mm of pulp. Next, the die rings and further mould can be compressed to about 0.7-0.8 mm and often less. The machined cut away cavities fill with fibre pulp which also remains there during pressing. It was found that it was possible to remove the lid from the ring after compressing, and that the notches resulting from the undercuts in the vacuum die ring remain on the lid. In figure 6 a detail of a cross section of a die is shown. It can be seen that the cavities are in fact are very shallow, and in fact a trade off between allowing removal or the produced lid, and providing proper and sufficient snapping of the lid on a container. In this embodiment, the walls of the cavities have rounded edges. In fact, the edges are often more rounded than indicated in the figure 5. The edges have can have a rounding as indicated in the cross section shown in figure 6. This allows better removal of the lid in mass production. In an embodiment, the wall of the counterpart can be straight. In this way, the pulp at the location of the undercuts or undercut will be compressed less than the pulp elsewhere. It was found that this provides a notch or notches which are a little more compressible than the further lid. It was found to provided better snap closure.
Figure 7 shows in radial cross section an alternative embodiment of a lid, showing in cross section the solid notch 7 as described above in the previous paragraph, in this embodiment having a lower density than the further lid. The lid snaps over rim 21 of cup 20. The rim 21 is here a rolled rim. Rim 21 has an upper surface 22. The top wall 2 in this embodiment continues via a curved part 14 into a curved locking wall 5. In this embodiment the earlier described flange 5 and locking flange 6 are combined into one curved locking wall 5. Curved part 14 runs from top wall 2 to below the upper surface 22. The curved locking wall 5 starts below the upper surface 22 of rim 21 and follows the rim 21 over at least an angle a. Notch 7 is provided, measured from the upper surface 22 of rim 21, below the widest part of rim 21. This, a good sealing and good snapping properties are combined. Here the angle a (the angle in radial direction) is between 110 and 180 degrees. In particular, it can be between 110 and 140 degrees. Here notch 7 is about 170-210 degrees remote, in a radial direction, from the starting position where said curved locking wall surface 5 is in contact with said rim. In the vicinity of notch 7, the curved locking wall surface is here free from said rim but keeps following it curvature (in radial direction). The locking wall with notch 7 in fact grabs around the rim 21. Notch 7 in this embodiment extends about 0.2-0.4 mm, in particular about 0.25-0.35 mm, from the surface of said locking wall. In this embodiment, notch 7 is below the maximum diameter of rim 21, snapping around rim 21. In the production process described above, the density of the notch is lower than the density of the further walls of the lid. In fact the density can be about 10%-50% less than the density of the further lid. This provides additional flexibility and thus snapping strength of the lid to the container. It is evident that the rolled rim 21 of figure 7 may also be provided as an inward rolled rim, although this is not usual. In such a situation the same lid snaps on the rim 21. This is in particular the case in a frustro conical cup.
It will also be clear that the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person which are within the scope of protection and the essence of this invention and which are obvious combinations of prior art techniques and the disclosure of this patent.