A PLASTIC LID

Abstract: A plastic lid (2) for closing a container opening in a container having a ring insert (3) with a central opening with at least one annular sealing surface (19, 20) for engagement with at least one annular sealing surface (14, 15) of the lid. Another radially extending annular rim (21) is provided on the lid, which rim is arranged to engage with the ring insert (3). The central part (11) of the lid is placed below a plane (17) through the annular rim (21), and for example in such a manner that the central part (11) is concave.

Description: A PLASTIC LID The invention relates to a plastic lid of the kind pre¬ sented in the preamble to claim 1. It has turned out that containers with matching lids in plastic, for example as presented in applicant's previous international patent application no. PCT/DK88/00011 (WO 88/05751), may advantageously be de¬ signed differently than presented, whereby further ad¬ vantages are achieved, without reducing the advantages and qualities as already presented in the international application. Experience has shown that when handled, containers with a mounted lid may be exposed to quite heavy loads and lateral pressure, resulting in deformation of the con- tainer lid or overpressure in the container space, i.e. the space limited by the container and the lid. This may happen, if a number of containers with lids are kept back on a conveyor before they are led on, for example to a labelling machine or the like. Momentary over- pressure may also arise due to stresses or the contai¬ ners falling over during transportation from one con¬ veyor to another. If the overpressure arisen is high enough, the container lid may burst off, if designed as presented in the above international application. It is the object of the invention to present a container lid which is designed in such a manner that it is appli¬ cable in containers with a ring insert, without the lid bursting off when exposed to even very heavy mechanical stresses. This is achieved by designing the container according to the invention as presented and characterized in claim 1. It is thus achieved that overpressure in the container will result in the radially extending annual rim of the lid engaging even more closely with the ring insert, be- cause the diameter of the rim is increased. If the lid according to the invention is designed as presented and characterized in claim 2, the load from any possible overpressure will be evenly distributed on the underside of the lid, so that the increase of the diameter is even all along the edge of the ring insert. It is thus rendered possible that the lid will remain firmly mounted in the container, even at very high over¬ pressures. This design moreover helps reducing the power needed for mounting the lid. The above increased advan¬ tages of the lid depend on the type of curvature applied for making the central part of the lid concave. The invention will now be explained in closer detail with reference to the drawing which shows a preferred embodiment of the invention, in that fig. 1 shows the upper part of a container with a lid according to the invention, partly as a side view and partly as a sectional view, fig. 2 shows a section as in fig. 1, but on a larger scale, and fig. 3 shows how the lid according to the invention reacts to pressure applied on the side of the container. Figs. 1 and 2 of the drawing show the upper part of a con- tainer with a lid according to the invention. The container 1 has a substantially cylindrical wall 4 with two internal, annual rims 5, 6 placed close to the opening and arranged to secure a ring insert 3 which by means of two ring walls 12, 13 defines an annual cavity 7 against the wall 4 of the container. The ring insert 3 has annual sealing surfaces 19, 20, in that the diameter of the sealing surface 19, which is the closer to the container opening, is smaller than that of the sealing surface 20, which results in an annual rimlike edge. The lid 2 has a central part 11 which gradually becomes a substantially axial part 10 which in turn becomes a sub¬ stantially radial part 9, in that all the lid parts are injection moulded in one piece in plastic. At the outer edge on the underside the lid 2 has a bevelling 18 for the outer edge of the lid to be able to rest on the upper edge of the uppermost rim 5, so that the upper edge of the rim 8 is flush with the upper edge of the radial lid part 9. This results in a plane area on top of the container lid and the container, which allows stacking of containers with a lid. At the foot of the axial part 10 the lid 2 has a radially extending annual rim 21 which is arranged to engage with the ring insert 3 as shown, so that a small annual tole¬ rance 16 appears between the sealing surfaces of the ring insert 3, which tolerance compensates for production tole- ranees etc. The lid 2 is provided with annual sealing sur¬ faces 14, 15 opposite the sealing surface 19, 20 of the ring insert 3. The central part 11 of the lid curves downwards so that it is concave and mainly below a plane (see the dot-and-dash line 17) through the rim 21. It is hereby achieved that any overpressure applied and attempting to press the lid part 11 upwards will result in the diameter of the annual rim 21 increasing, whereby the lid becomes even more firmly moun¬ ted. Fig. 3 shows how overpressure may arise inside the contai¬ ner. On an accumulation conveyor a container may be affect¬ ed by the pressures P of the neighbouring container. Due to the particular lid design this will result in a downward- directed force which will attempt to press the lid further down into the container, while at the same time a vertical upward-directed force, which occurs because of the over¬ pressure in the container, will attempt to make the lid burst off. Tests have established that provided the lid is designed as described in the present application, the re¬ sulting force F will become downward-directed and the lid will become slightly deformed as shown with the dot-and- dash line. Consequently the lid will not burst off, even if it is exposed to strong forces, like for example lateral forces, which result in high overpressure in the container. If the lateral forces P affect the container further down, so that the lid is not directly deformed by these forces, overpressure will occur inside the container anyhow. How¬ ever, not even this will cause the lid to burst off, since the overpressure will affect the concave lid part 11 and attempt to press it upwards. Hereby the diameter of the rim 21 is increased; the lid becomes even more firmly mounted and will only burst off if exposed to extraordinary over¬ pressures.

Claims: CLAIMS 1. A plastic lid (2) for the closing of a container ope¬ ning in containers (1) of the bucket or beaker type, and where an internal ring insert (3) is provided in the vici¬ nity of the opening, which ring insert (3) has a central opening with at least one annual sealing surface (19, 20) which is arranged to engage with at least one annual sealing surface (14, 15) of the lid (2), and where the lid (2) has a radially extending annual rim (21) which is arranged to engage with the ring insert (3) in order to ensure that the lid remains firmly mounted, c h a r a c - t e r i z e d in that the lid comprises a central par (11) which is substantially placed on the one side of a plane (17) through the annual rim (21), while the rest o the lid is placed on the other side of the plane. 2. A plastic lid according to claim 1, c h a r a c t e ¬ r i z e d in that the central part (11) is concave see from the outer side when the lid is mounted on a container.

Inventors: LUND CARSTEN, LUND, CARSTEN
Applicants: PANTHER PLAST AS, PANTHER PLAST A/S
Application year: 1990
Main classification: B65D39
IPC codes: B65D43