GB2267667A - Seaming of containers - Google Patents

Abstract

A contoured seaming roll 100 for forming a peripheral seal, particularly a triple seam seal, has first 106 and second 108 seaming roll portions which define a peripheral seaming profile 107. The first and second seaming roll portions 106, 108 are mounted on a cylindrical portion of a hub 101 which is rotatably mounted on a fixed shaft 102. The first seaming roll portion 106 is, in use, fixedly secured to the hub 101. The second seaming roll portion is displaceable along the hub with respect to the first seaming roll portion 106, but is biased into engagement with the first seaming roll portion 106 by a resiliently deformable ring 112 which is in contact with the undersurface of the second seaming roll portion 108. The seaming profile of the roll can thus be altered during seaming. <IMAGE>

Description

DESCRIPTION SEAMING OF CONTAINERS The present invention relates to a method and apparatus for seaming containers, for example for sealing cylindrical metal cans.

It is known to secure a metal end cap of a container to a tubular metal body by a process known as seaming. This is achieved by the use of machines with rotary heads which carry seaming arms with seaming rollers attached. The rollers are rotatably mounted and are specially contoured to form a rolled seam. The shapes of the rollers determine the type of seam produced. By using such machines a so-called "double seam" of folded material can be produced which is five layers thick, compared with a single layer thickness over the remainder of the container.

The steps for forming a conventional double seam are illustrated in Figs. 3 to 6. The steps are described briefly below: Referring to Fig.3, the upper periphery of a cylindrical metal wall 10 (hereinafter referred to as "portion 10") and the periphery of a metal disc 12 (hereinafter referred to as "portion 12") which is intended to form one end of the can, are initially brought together along part of their respective lengths via a seaming chuck 16 so as to contact one another along this part.

A first seaming roll 20 is then moved towards seaming chuck 16 to force portions 10 and 12 into a recess 18 of a seaming profile of the first seaming roll 20. This causes an end portion 14 of the upper periphery 10 which has already been supplied with a curl, known as a pre-curl (as will be explained later) to curl further so that a folded configuration is formed as shown in Fig.4.

During the seaming process the seaming roll 20 (which is free-running on bearings) is rotated around the can or the can itself is rotated thereby causing the seaming roll 20 to rotate (depending upon the type of seamer). This relative movement is shown by arrows A and B in Fig.4. The recess 18 (seaming roll profile) extends circumferentially around the seaming roll 20 so that during seaming the part of the can being seamed is always located therein.

At the stage shown in Fig.5 a seam precursor 21 has been formed, but seaming is not complete, as the layers of the seam precursor 21 have not been compressed together to the desired degree, there being a larger central space 22. Hence a second seaming operation is performed in which seam 21 is compressed against seaming chuck 16 to force it into a recess 24 in a second seaming roll 26. This is shown in Fig.6, where seam 21 can be seen to have been compressed to form a seam having five adjacent layers of tin-plate:layers 26,28,30,32 and 34.

Although the double seam described with reference to Figs. 3 to 6 is adequate for many purposes, it does not always result in a seam which is sufficiently strong to comply with certain safety regulations. In particular, many containers having a double seam fail to comply with United Nations Regulations Regarding The Carriage of Dangerous Goods, especially in respect of containers of five litres and above.

In order to comply with such regulations socalled "triple seaming" has been used. This results in a strong seam which is seven layers thick.

Figs. 7 to 10 illustrate the steps in the formation of a triple seam using conventional apparatus, as described briefly below: Fig.7 is a cross-section showing a seaming chuck 40 being used to press and locate portions 10 and 12 together ready for seaming. To begin using the seaming roller profile (18) portion 41 is known as a pre-curl and is formed prior to seaming beginning.

Fig.8 shows a vertical cross section through a triple seaming apparatus, with seaming chuck 40 being used to press portions 10 and 12 together and locate them ready for the seaming to begin. Arrow 'A' shows the direction the machine forces the seaming roller towards seaming chuck 40 during seaming. Wall 45 is specifically contoured to form recess 42. Portions 10 and 12 curl back on themselves during seaming. Dotted line 43 indicates the location of pre-formed pre-curl 41 prior to seaming. It can thus be appreciated that pre-curl 41 is necessary to allow curling of portions 10 and 12 to take place in the appropriate manner to form a seal.

A second stage of the process is shown in Fig.9, wherein a second seaming roll 46 having a different shaped wall 47 defining a recess 48 is used to produce further curling of portions 10 and 12.

Finally a third stage occurs, as shown in Fig.10.

Here a third seaming roll 50 is used. This has a wall 51 defining a comparatively shallow recess 52 which allows portions 10 and 12 to be compressed (in a similar manner to that shown in Fig.6 for double seaming) to give a finished triple seam 54. The triple seam 54 can be seen to have seven layers 56,58,60,62,64,66 and 68.

Since the triple seam 54 is thicker than a double seam, apparatuses for producing it have been provided with rollers having walls defining deeper contoured recesses for forming the seam than would be used for forming a double seam. Thus, in order to meet stringent standards such as the aforementioned United Nations regulations, it has been necessary to purchase expensive triple seaming machines or to try to adapt existing double seaming machines to perform triple seaming. The adaptation of existing machines has been difficult and time consuming. It usually requires a complete new seaming head design and manufacture; possibly at half of the cost of the original machine.

Even then, reliability of performance and seaming has been doubtful.

This is why machine manufacturers have built and designed complete new machines to facilitate triple seaming.

The aforementioned disadvantages are overcome or at least alleviated by the present invention.

According to a first aspect of the present invention there is provided a contoured seaming roll for forming a peripheral seal, comprising first and second seaming roll portions defining a seaming profile, the first portion being displaceable relative to the second portion in order to permit variation of the seaming profile of the roll during seaming.

Preferably the sections are, in use, separable by the material forming the seal as rolling occurs.

The profile of the seaming roller is different in its expanded form from its unexpanded form and this change in profile enables material which will eventually form a triple seal to be coiled in the form of a seven layer coil in a single seaming operation.

Previously a two-stage process using two different seaming rolls was necessary for this operation.

It is then only necessary to compress the coil to produce an effective triple seal.

The different sections may be biassed (e.g. by spring loading or by the compression of resilient, deformable material) so as to act against separation of the first and second portions of the seaming roll caused by the coiling of material used to form the seal.

It is not, however, essential that the displacement of the first and second seaming roll portions occurs due to the separation of different sections of the seaming roll from one another. For example, the seaming roll can be provided with resilient, deformable material at a region which defines a recess so that deformation of this material during seaming allows the displacement to occur.

Alternatively, expansion can be facilitated by means of interconnected parts which are e.g. pivoted or hinged together.

According to a second aspect of the present invention there is provided a method for use in producing a triple seam on a container which comprises: a) directing material from parts of the container towards a seaming roll comprising first and second roll portions defining a seaming profile so that the material coils around itself and causes the first roll portion to displace relative to the second roll portion so that the seaming profile is changed; b) allowing the material to continue to coil until a coil seven layers thick has been produced.

The coil can then be compressed using a further seaming roll to give a finished triple seam. The further seaming roll need not have a variable seaming profile.

Although the present invention is particularly useful for triple seaming, it can be used in double seaming by preventing the displacement of the first roll portion relative to the second roll portion.

This can be achieved e.g. by locking, clamping or pressing the portions of the seaming roll together, which would otherwise become spaced from one another as the material used to form the seam is coiled.

It is however, possible to allow limited expansion of the recess to enable double seaming of a rectangular container to be efficiently achieved.

This method produces a more reliable seam than is possible with conventional double seaming techniques for such containers. It allows the corner regions of such containers to be accommodated within the seaming recess by limited expansion of the recess.

According to a third aspect of the present invention, there is provided a method of adapting a double-seaming apparatus to produce triple seams comprising replacing a double seaming roll with a seaming roll according to the present invention.

A specific embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: Fig.l shows a seaming roller 100 of the present invention; and Fig.2 shows an enlarged cross-sectional view of plates 106 and 108 of the seaming roller of Fig.1.

Seaming roller 100 comprises a hub 101 which is rotatable about a fixed centre shaft 102. Seaming roller 100 also comprises an upper half seaming groove plate which is fixed relative to the shaft 102 and a lower half seaming groove plate 108 which is displaceable relative to the shaft 102 and the upper plate 106. The outer peripheries of the upper and lower plates 106,108 define a seaming profile, including a circumferential recess 107 shown located between plates 106 and 108. An annular disc 112 is provided below plate 106 and is formed of a resilient, deformable, rubber material or springs etc., and as will be described, allows limited movement of the lower plate 108 relative to the upper plate 106 in order to vary the seaming profile.

A pressure plate 111 is located below and in contact with the resilient ring 112 and by adjustment of a number of bolts 110 which pass through threaded apertures in a circumferential flange 113 of the hub, can be raised or lowered so as to put the resilient ring 112 under various degrees of compression. This in turn causes the plate 108 to press against the plate 106 with varying force.

A number of locking screws 114 which pass through a radially extending threaded aperture in the upper portion of the hub 101 and engage in a recess 119 in the shaft 102 serve to hold the plate 106 in fixed position relative to the hub 101.

The seaming roller 100 is also provided with a locking plate 116 which lies adjacent a setting washer 118 and which functions to restrict vertical movement of hub 101 along shaft 102. Screw 117 serves to secure locking plate 116 to centre shaft 102.

Smooth rotation of hub 101 about shaft 102 is facilitated by bearings 120, which are lubricated via grease nipple 122. Circlips 124 function to hold the bearings 120 in position.

Fig.2 shows a partial cross-section through plates 106 and 108 when roller 100 is in use for triple seaming.

The periphery of an end wall 20 and the periphery of a side wall 10 of a cylindrical can to be formed are shown after having been pushed into recess 104 by chuck 105.

Initially, the plates 106 and 108 are held together due to the force exerted on plate 108 by the annular resilient disc 112. However, as peripheries 10 and 12 curl around each other and form an increasingly tight coil, the coil exerts an increasing force on the upper and lower plates 106 and 108 which eventually causes them to separate, so that a gap 128 is formed. The separation of plates 106 and 108 alters the profile of the roller by increasing the size of recess 107 so that it can accommodate more material and a coil 130 can thus be formed in recess 107 which is seven layers thick. At this stage the annular disc 112 (see Fig.l) is highly compressed so that it exerts a large force on plate 108 in the direction of plate 106. This prevents further coiling occurring so that the coil 130 of the desired thickness of seven layers is obtained. This coil 130 is then removed and compressed to give a strong triple seam in the same manner as shown in Fig.8.

Existing double seaming apparatuses can be readily and cheaply converted to perform triple seaming by providing one or more seaming rolls of the present invention, dependent on the type of machine to be converted.

It should be appreciated that the present invention can be used to form double seams as well as triple seams. This can be achieved by using pressure screws 110 to compress annular disc 112 (see Fig.l) to a high degree so as to ensure that plates 106 and 108 are kept close together during the whole seaming process.

Indeed, by using the present invention, improved double seaming can be achieved on rectangular containers. Using prior art methods, the corners of such containers have often been poorly sealed, since they often do not fit properly into the recess defined by a wall of a seaming roll used to form the seam.

The present invention allows the size of the recess to be increased slightly to accommodate such corners.

Claims (14)

1. A contoured seaming roll for forming a peripheral seal, comprising first and second seaming roll portions defining a seaming profile, the first portion being displaceable relative to the second portion in order to permit variation of the seaming profile of the roll during seaming.

2. A seaming roll as claimed in claim 1, comprising biasing means which bias the first and second seaming roll portions towards each other.

3. A seaming roll as claimed in claim 2, wherein the biasing means comprises resiliently deformable material.

4. A seaming roll as claimed in claim 3, wherein the resiliently deformable material biases one of the sealing roll portions.

5. A seaming roll as claimed in any of the preceding claims, comprising a hub upon which the first and second seaming roll portions are mounted.

6. A seaming roll as claimed in claim 5, wherein one of the seaming roll portions, in use, is fixed relative to the hub and'the other of the seaming roll portions is displaceable relative to the hub.

7. A seaming roll as claimed in claim 5 or claim 6, wherein the hub comprises a longitudinal body portion upon which the seaming roll portions are mounted, the movable seaming roll portion being movable in a direction parallel to the longitudinal axis of the longitudinal portion of the hub.

8. A seaming roll as claimed in any of claims 5 to 7, comprising a mounting plate movable relative to the hub and a resiliently deformable material located between the mounting plate and the movable seaming roll portion.

9. A seaming roll as claimed in claim 8, comprising means for adjusting the position of the mounting plate with respect to the hub.

10. A seaming roll as claimed in any of claims 5 to 9, comprising an axle upon which the hub is rotatably mounted.

11. A seaming roll as claimed in claim 10, comprising bearings for mounting the hub on the axle.

12. A method for producing a seam on a container comprising directing material from part of the container towards a seaming roll as claimed in any of the preceding claims, thereby causing the material to coil around itself and causing the first seaming roll portion to be displaced relative to the second seaming roll portion in order to change the seaming profile, and continuing the coiling of the material.

13. A contoured seaming roll for forming a peripheral seal, substantially as herein described, with reference to, and as illustrated in, Figs. 1 and 2 of the accompanying drawings.

14. A method of forming a seam on a container, substantially as herein described, with reference to, and as illustrated in, Figs. 1 and 2 of the accompanying drawings.