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(11) | EP 0 108 462 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Preserving tin |
| (57) The invention relates to a preserving tin having a wall provided with a contraction
extending around the circumference. Such a wall-ironed container is known and used for packing inter-alia products filled in the hot state. As a result of the subatmospheric pressure occurring in the tin after closure and cooling the known tin tends to collapse, that is to say, to exhibit indentations in the body. For this purpose said, at least one contraction is provided, which serves as a reinforcing element. However, the great disadvantage of such a contraction is that the axial resistance is drastically reduced so that the stacking height of the tins is limited. The invention has for its object to construct a preserving tin in a manner such that there is no risk of collapsing, whilst nevertheless the axial resistance is fully maintained. Thereto the invention proposes a preserving tin of the kind set forth in the preamble, in which the edges of the contraction are pressed substantially one against the other. |
[0001] The invention relates to a preserving tin having a wall provided with a contraction extending around the circumference.
[0002] Such a wall-ironed container is known and used for packing inter alia products filled in the hot state. As a result of the subatmospheric pressure occurring in the tin after closure and cooling the known tin tends to collapse, that is to say, to exhibit indentations in the body. For this purpose said, at least one contraction is provided, which serves as a reinforcing element. However, the great disadvantage of such a contraction is that the axial resistance is drastically reduced so that the stacking height of the tins is limited.
[0003] The invention has for its object to construct a preserving tin in a manner such that there is no risk of collapsing, whilst nevertheless the axial resistance is fully maintained. In this respect the invention proposes a preserving tin of the kind set forth in the preamble, in which the edges of the contraction are pressed substantially one against the other.
[0004] In general it will be necessary to exert an axial force on the preserving tin in order to cause the edges of the contraction to approach one another. This requires an additional production step. According to the invention, in order to avoid said additional production step, the or each contraction may be dimensioned such that after the tin is filled with a hot mass, the subsequent closure of the tin and the cooling of the filled tin the edges of the contraction are pressed against or substantially against one another by the subatmospheric pressure caused by cooling.
[0005] After the tin is filled and closed the edges of the contraction can be advantageously pressed towards one another either by a mechanical operation or under the influence of the pressure difference between the atmosphere and the interior of the tin. Since the volume of the tin is reduced, the pressure in the tin becomes accordingly higher so that a smaller wall thickness will be sufficient. In all cases the tin is stiffened axially and radially.
[0006] The invention will now be described more fully with reference to the drawing showing an arbitrary embodiment.
Fig. 1 a cylindrical preserving tin having a contraction extending around the circumference,
Fig. 2 a detail II of Fig. 1,
Fig. 3 the tin of Fig. 1 in the state in which the edges of the contraction are substantially pressed against one another and
Fig. 4 shows a cylindrical preserving tin 1 having a cylindrical wall 3 provided with a contraction 2 extending around the circumference.
Fig. 2 shows the contraction 2 on an enlarged scale. The arrows 4 indicate the distance between the edges of the contraction.
Fig. 3 shows the same tin 1. However, in the state shown in Fig. 3 the edges of the contraction 2 are pressed towards one another. To indicate the difference from Fig. 1 the contraction is designated by reference symbol 2f. It should be noted that pressing the edges towards one another may take place in a separate production step, in which an axial force is exerted on the tin either prior to or after filling and the closure thereof or as a result of the occurrence of subatmospheric pressure in the tin owing to filling the tin with a hot mass, the subsequent closure of the tin and the subsequent cooling of the filled tin.
Fig. 4 shows the contraction 2' on an enlarged scale. The distance 4' between the edges, as will be apparent from a comparison between 4 and 2, is appreciably smaller than the distance designated by 4 in Fig. 2. When stacking a plurality of tins, the edges can be pressed against one another so that the axial resistance becomes equal to that of a tin not provided with a contraction.
[0007] It is noted that the distance 4' may even be zero. For obtaining a satisfactory stackability it is, however, sufficient for the edges to be relatively near one another so that when a stack is formed the edges are pressed against one another.
[0008] The invention is not limited to a preserving tin with only one recess of the kind described. Other numbers of recesses may be used.
[0009] Other shapes of the contraction provide the same desired result. Therefore, the invention is not limited to the shape shown in the drawing. It is furthermore possible to subject the preserving tin to an aftertreatment such that the contraction formed is pressed substantially against the inner face of the cylinder wall. In this way a substantially flat wall can be obtained, which has nevertheless all technical advantages of the invention.