GB2318785A

GB2318785A - Metal container with ring, lid and base made from equal diameter blanks

Info

Publication number: GB2318785A
Application number: GB9722695A
Authority: GB
Inventors: John Ewart Parker
Original assignee: Impress Metal Packaging Ltd
Current assignee: Trivium Packaging UK Ltd
Priority date: 1996-10-26
Filing date: 1997-10-27
Publication date: 1998-05-06
Anticipated expiration: 2017-10-27
Also published as: GB9722695D0; EP0838282A1; GB9622305D0; GB2318785B

Abstract

A metal container, such as a paint can, has its ring 10, lid 14 and base (16, fig 7) each made from circular blanks of the same diameter and the same material. The blanks may have the same gauge and may be made by shearing from a sheet. The invention provides a slim ring-lid combination which reduces the internal pressure in the container when the lid is fitted. A method of making such a container is also disclosed.

Description

This invention relates to methods of making metal containers, and is particularly concerned with methods of making metal cans for paint and other liquids. The invention is also concerned with metal containers made by such methods.

A continuing aim in the manufacture of metal cans is to reduce the cost of manufacture. Because of the quantities in which such metal cans are made, even a very small reduction in the unit price has a significant effect over the course of a year for example. Metal cans incorporate a cap and ring at the upper end of the cylinder and what is referred to as an "end" at the lower end of the cylinder. Traditionally, the cap, ring and end have been made from different materials and/or of different gauges and/or with different amounts of temper. This means a relatively complex operation for the preparation of these three parts of the can, requiring either a multiplicity of shearing machines to produce the blanks or alternatively changes to be made to the operation of the shearing machines from component to component. Also, with these various differences in materials, gauges and temper, one has to maintain a large inventory of components, requiring substantial storage space and careful attention to stocks.

It is an object of the present invention to reduce the costs of production of the cap, ring and end of a metal can by using a common material, tempered to the same degree for all three parts.

In accordance with the present invention there is provided a method of manufacturing a metal container which has a ring and a cap at one end and an end at the other end, which comprises producing circular blanks of the same diameter from the same material, and from said blanks producing a ring, a cap and an end having respective different profiles.

Preferably, the end, the cap and the ring are made from material of the same gauge, with the end, cap and ring thus each comprising the same mass of material.

Also in accordance with the present invention there is provided a metal container having an end portion at one end, and a ring and cap at the other end, wherein the end portion, the cap and the ring are each made from circular blanks of the same diameter and of the same material.

Preferably, each blank has the same mass of material.

It is a surprising fact that these three components of the can can be made each from the same diameter blank, appropriately shaped in each case. This gives considerable advantages in the manufacturing process. By having commonality for the material, the diameter of the blanks and the temper of all three parts one can substantially simplify the production process and make savings in terms of raw materials, stocks of parts, etc. By using blanks of the same diameter for each of the three component parts one can simply shear circular blanks from the raw material, i.e. tinplate, and maintain a stock of these. One can then choose at will whether these are to be made into ends, caps or rings. One thereby achieves substantial savings in the shearing process to produce the blanks, because one does not have to make adjustments to the shears to cater for the manufacture of three different parts: all three are made from the same diameter blanks.

Containers made in accordance with the present invention also have a further consequential advantage. In the filling of paint cans with liquid paint there is a continuing problem of lid lift. In other words, when the lid is pushed into place in the ring at the top of a can, this creates a piston effect, compressing the air within the can and occasionally causing the lid to rise or become detached from the can, with accompanying spillage of the paint and the need then to stop the filling machine. Not only does one then have the problem of cleaning the machine, but one also has the loss of production time while the machine is at a standstill.

Attempts have been made to overcome this problem by for example providing venting in the cap so that the internal pressure is reduced. Attempts have also been made to improve the coefficient of friction between the cap and the ring, so that the fitting of the cap can be accomplished without the exertion of so much force. One of the problems in this area is that the conventional cap has a substantial depth, so that the cap has to travel over a substantial distance during its fitting into the ring. This contributes to the increase in pressure within the can and can also cause distortion of the opposite end of the can. This is particularly so in the event that the can is overfilled.

The use in accordance with the present invention of a common diameter for the blanks which will result in the cap, the ring and the end means that one can also reduce the problem of lid lift by the use of a slim cap and slim ring, while yet achieving adequate sealing. It has been considered heretofore that a substantial depth is required for the cap and that one could therefore not use a common diameter blank for that component as well as for the other components.

However, that has been found not to be so.

In order that the invention may be more fully understood, one presently preferred embodiment of metal container will now be described by way of example and with reference to the accompanying drawings. In the drawings: Fig. 1 is a transverse section through a can ring to be fitted to the can; Fig. 2 is a view, on an enlarged scale, of the left-hand end of the ring shown in Fig. 1; Fig. 3 is a transverse section through the lid or cap to be fitted to the ring of Figs. 1 and 2; Fig. 4 is a view, on an enlarged scale, of the left-hand end of the cap shown in Fig. 3; Fig. 5 shows the left-hand end of the cap when fitted into the ring; Fig. 6 illustrates how the caps can be stacked; and Fig. 7 is a transverse section through the can end.

The ring shown in Figs. 1 and 2 and indicated generally at 10 is of tinplate and is intended to be fitted to the one end of a cylindrical container (not shown) such as a paint can. The other end of the cylindrical container is closed by an end which is shown in Fig. 7 and which will be referred to later. The ring 10 has a circumferential looped portion 12 into which the cap or lid shown in Figs. 3 to 5 is designed to fit. The depth of the looped portion 12 is relatively shallow, for example of the order of 4.9mm. The overall depth of the ring 10 is of the order of 6.5mm. The general configuration of the ring is conventional. Preferably, the ring is made in one of two alternative gauges of material, either 0.25mm or 0.19mm. The diameter of the circular blank from which the ring 10 is made before it is shaped is for example of the order of 171mm for a 2.5 litre can.

The cap or lid shown in Figs. 3 to 5 and indicated generally at 14 is made from the same material as the ring 10, tempered to the same degree, and from a circular blank of the same diameter as the blank from which the ring is made. The depth of the cap is 8.4mm. Again, the cap can be made of material which is 0.25mm or 0.19mm thick. As can be seen from Fig. 6, the caps 14 can readily be stacked after having been given their profile.

Fig. 7 shows the end 16 of the can, which is made from the same material as the cap 14 and ring 10 and which is tempered to the same degree. The diameter of the circular blank from which the end 16 is made is the same as the diameter of the blank used for the ring 10 and for the cap 14.

The end 16 is provided with a profile such as that shown in the drawing in order to strengthen the end against deformation when the container is filled with liquid such as paint.

As mentioned above, the three component parts, namely the ring, the cap and the end are all made of the same material, tempered to the same degree. Preferably, all three components are also made from the same gauge of sheet material, as a result of which the mass of each of these component parts is also the same. Each component is then shaped differently in a stage following the shearing of the blanks from the raw sheet material. One therefore just needs a single stock of circular blanks, from which one can create caps, rings or ends as desired.

With a can made in accordance with the present invention, internal pressure tests have shown that a substantial reduction is achieved both in the internal pressure and in the total internal forces within the can when lidding takes place.

For example, with a 2.5 litre can, the internal pressure (20.531b), using a lacquered ring and lacquered cap, is less than half the internal pressure (47.021b) which is found using a standard ring and cap. This is a direct consequence of the use of a slim cap, which itself is a consequence of the use of a common diameter blank for the cap, ring and end. With the present invention it has been clearly demonstrated that one can use a suitably profiled, slim cap which provides excellent sealing and which achieves a substantial reduction in internal pressures within the can when fitted.

Claims

CLAIMS:

1. A method of manufacturing a metal container which has a ring and a cap at one end and an end at the other end, which comprises producing circular blanks of the same diameter from the same material, and from said blanks producing a ring, a cap and an end having respective different profiles.

2. A method as claimed in claim 1, which comprises producing all said blanks from material of the same gauge.

3. A method as claimed in claim 1 or 2, which comprises shearing the blanks from sheet material.

4. A metal container having a ring and a cap at one end and an end at the other end, wherein the ring, the cap and the end are each made from circular blanks of the same diameter and of the same material.

5. A metal container as claimed in claim 4, in which the blanks are all made from material of the same gauge.

6. A metal container as claimed in claim 4 or 5, in which the blanks have a thickness of the order of 19mm.

7. A method of manufacturing a metal container, substantially as hereinbefore described with reference to the accompanying drawings.

8. A metal container, substantially as hereinbefore described with reference to the accompanying drawings.