GB2056326A - Containers - Google Patents

Abstract

A container comprises two halves (10, 12) each manufactured by shear-forming from a circular metal blank, e.g. of stainless steel. The halves may be secured together by welding. <IMAGE>

Description

SPECIFICATION Containers for liquids This invention relates to flat-based metal containers for liquids, especially containers of the kind comprising two halves which are secured together in inverted relation to form the container, the container being flat-based to enable it to be free standing.

Hitherto, the two halves of such containers have have tended to be cylindrical and have usually been manufactured by the deep drawing technique especially where the material employed is mild steel or stainless steel. Manufacture by this method is expensive but, so far as we are aware, no satisfactory and less expensive alternative has been found for the manufacture of stainless steel flat-based containers.

According to the present invention therefore we provide a flat-based metal container for liquids comprising two halves of truncated conical configuration joined together in inverted relation at their larger diameter ends, each container half having been formed from a generally cylindrical blank of the metal, preferably stainless steel, by rotating the blank about its axis of symmetry while a central portion of the blank is held against the smaller end of the truncated mandrel and progressively drawing the annular area of the blank which projects beyond said central portion against the conical surface of the mandrel with a shearing action such that plastic deformation of the material occurs resulting in a conical wall which is of lesser thickness than said central portion.

Preferably the angle of the wall with respect to the axis of symmetry is at least 1 50 (i.e.

corresponding to an apex angle of at least 300).

Thus, the container has a flat base at each end thereof, corresponding to the central portions of the respective blanks. One end may be equipped with handles and a connector or the like for admission and withdrawal of the liquid.

Preferably the two container halves are welded together and to protect the joint during subsequent handling of the container, the joint may be encircled by a rolling ring which may be of stainless steel or mild steel for example.

Although the method for forming the two container halves is already a known technique in the metal spinning art (the technique being usually known as shear forming), it has not been previously proposed for fabrication of containers of the kind with which the invention is concerned and, in any event, would not be suitable for producing cylindrical container halves.

The present invention is based on the recognition that satisfactory containers can be produced if the blanks are shear-formed not to cylindrical configuration but to conical configuration (preferably with an apex angle of at least 300) and the surprising result that such double coned containers can withstand substantial working pressures somewhat in excess of what could be expected having regard to their configuration and the reduced bore thicknesses resulting from shear-forming.

Shear-forming has the additional advantage that the production time is relatively short compared with other methods and components of high accuracy and good internal and external surface finish can be obtained.

One example of the invention is shown in the accompanying drawing, the sole figure of which is a longitudinal section through a stainless steel container intended for storage of liquid detergents.

Referring to the drawing, the container comprises two halves 10, 12 both of truncated conical configuration welded together at their free edges. As both halves 10, 12 are formed by the shear-forming technique, it will be appreciated that the thickness of the conical walls thereof will be less than the circular base portions 14, 16 and the conical walls will progressively reduce in thickness towards the free edges thereof. The container is intended to be stood on its base portion 16 in normal use but to facilitate handling, whilst at the same time protecting the welded joint between the two halves 10, 12, the container is provided with a rolling ring 18 of channel configuration which tightly encircles the joint.The ring 18 need not be physically connected to the container as it will be maintained in place by virtue of the oppositely sloping sides of the two container halves in the region of the joint.

The base portion 14 of the container is provided with for example a connector 20 for admission and withdrawal of the liquid and handles 22.

As previously mentioned, the container halves will be formed from circular blanks by the shearforming technique in which each blank is held with its central portion against the smaller diameter end of a frusto-conical mandrel of form block, the assembly of mandrel and blank is rotated about the axis of symmetry of the mandrel and blank and the disc is formed by the drawing action of a roller which moves parallel to the direction of workpiece travel and which gives the workpiece its shape in one step. The working pressure must be adjusted in such a way that the part of the disc which has not yet been processed stays vertical to the axis of rotation. In this way, the material is deformed plastically in the axial direction resulting in a reduction in the thickness of the disc material.

In an alternative embodiment of the invention, the bottom end of the container may be provided with a ring to facilitate stacking, the top end being formed, again by shear forming with a ledge or step, with which the stacking or so-called chimb ring can nest. The stacking ring will be bonded to the bottom end of the container so as to project axially and will conveniently terminate in an inwardly curled over portion which curls back in a circular arc through almost 3600.

The step or ledge will have a flat shoulder conveniently lying in a plane parallel to that part of the blank which remains undeformed and a sloping side having an angle of inclination of 150 or more. The width of the ledge will be only a small proportion of the radius of the undeformed central part of the blank.

The ledge may be formed by providing the main mandrel or forming block with a projection on its small diameter end. Initially the blank is shearformed against a conical side wall of the projection and thereafter the blank is shear formed against the conical wall of the main mandrel either after the projection has been removed or with the projection still in place. The projection is conveniently releasably securable to the smaller end of the main mandrel.

In a modification, the top container half can be shear-formed without a ledge and then the ledge may be shear-formed in a separate, subsequent operation.

Claims (9)

1. A flat-based metal container for liquids comprising two halves of truncated conical configuration joined together in inverted relation at their larger diameter ends, each container half having been formed from a blank of the metal by rotating the blank about its axis of symmetry while a central portion of the blank is held against the smaller end of a truncated mandrel and progressively drawing the annular area of the blank which projects beyond said central portion against the conical surface of the mandrel with a shearing action such that plastic deformation of the material occurs resulting in a conical wall which is of lesser thickness than said central portion.

2. A container as claimed in Claim 1 in which the angle of the wall with respect to the axis of symmetry is at least 150.

3. A container as claimed in Claim 1 or 2 in which the container halves are welded together at the larger diameter ends thereof.

4. A container as claimed in any one of Claims 1 to 3 in which a rolling ring is assembled to the container at the joint between the container halves.

5. A container as claimed in any one of Claims 1 to 4 in which one of the container halves is provided with a ledge or step adjacent its smaller diameter end formed by shear forming and the other container half is provided with a stacking ring for cooperation with a ledge or step on another similarly formed container.

6. A container substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

7. A method of making a flat-based metal container comprising shear forming separate generally circular metal blanks by rotating each blank about its axis of symmetry while a central portion of the blank is held against the smaller end of a generally frustro-conical mandrel and progressively drawing the annular area of the blank which projects beyond said central portion against the conical surface of the mandrel with a shearing action such that plastic deformation of the material occurs resulting in a conical wall which is of lesser thickness than said central portion, and subsequently securing the shearformed blanks together at the large diameter ends thereof.

8. A method as claimed in Claim 7 in which the angle of the wall with respect to the axis of symmetry is at least 15%.

9. A method of making a flat-based metal container substantially as hereinbefore described with reference to, the accompanying drawings.