Methods for forming containers

Abstract: A pre-formed (e.g. injection moulded) container body of flexible resilient plastics material is subjected to a subse­ quent cold-forming operation so that it is permanently de­ formed into a required configuration. For example, a desired container mouth configuration may be produced or handle-­ retaining recesses may be formed.

Description: This invention is concerned with methods for forming containers. Conventionally, container bodies made for flexible, resilient plastics material are formed in their required final shape in a single moulding operation, e.g. by injection moulding or blow moulding. It is an object of the present invention to provide improved methods and apparatus for forming container bodied of flexible, resilient plastics material and attaching handles thereto. Larger plastics containers such as buckets require handles to carry them. These handles are mainly manufactured from steel wire or plastics. To hold the handle, the plastics container is normally moulded with handle lugs, projecting from the outer surface. This design causes complication in the mould resulting in lower production speed and higher capital cost, and also complicates decoration of the container - both printing and labelling wise. A design maintaining a smooth outer surface of the container by recessing the handle lugs into the surface, is known. However, this design requires a split or collapsible core of the mould, which is very costly and slows down the production speed. According to the invention there is provided a method of manufacturing a container and handle combination characterised by the combination of steps that a pre-formed container body of flexible, resilient plastics material is subjected to a cold-forming externally applied pressure operation in which the material is permanently deformed and stretched inwardly wherein two oppositely disposed inwardly extending hollow recesses are produced in the side wall of the container body by said externally applied pressure, said recesses being adapted to receive projections on a handle for the container, forming the handle having projections and enlarged heads on the substantially opposite ends, and forcing said enlarged heads into said hollow recesses causing said enlarged heads to expand the walls of said recesses to removably retain said projections. The method may include positioning a pair of dies having bores therein internally of said container at substantially diametrically opposite positions on said side walls, and a pair of pistons outside said side walls in alignment with the bores of said dies, displacing the plastics material of said side walls into said bores by applying pressure thereto by moving said pistons against the side walls and into said bores so forming said opposite disposed inwardly extending hollow recesses. The bores of said pair of dies may be positioned at subtantially right angles to said side walls. During the displacing step the inwardly extending hollow recesses may be formed with wall thicknesses less than the thickness of the container side walls. An enlarged head on pivotal projections on the handle may expand the walls of the intrusions inside the side wall of the container, if the walls of the intrusions have sufficiently thin wall thickness. This will "catch" the handle and make the fixture sufficient for normal use. If, however, one needs to take off the handle to change the label, it is still possible to pull the handle off the container and to replace it, when needed. The foregoing and further features of the invention may be more readily understood from the following description of a preferred embodiment thereof, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a sectional side view of apparatus for post forming handle-receiving recesses in a plastics container; Figure 2 is a view on a larger scale of parts shown in Figure 1 after formation of a recess, Figure 3 is a view on a larger scale of a pivotal projection on a handle received in a recess, and Figure 4 is a part sectional view showing a container with a handle fitted. In the embodiment, the container is made of flexible, resilient plastics material, e.g. polypropylene. Figure 1 shows a pre-formed plastics container body 50 with two dies 51 positioned internally at diametrically opposite positions. Each die 51 has a through bore in which is reciprocably disposed a plunger 52 biassed outwardly by a spring 53 to provide a spring-loaded bottom for the die. The springs 53 have adjustable supports 54 so that the resistance to movement of the plungers 52 can be adjusted. Outside the container body are two pneumatically actuated pistons 55 having convex projections 56 which cooperate with concave recesses in the outer ends of plungers52. In use, the pistons are forced inwardly so that the projections 56 deform the side wall of the container body under the constraint imposed by the plungers 52 to form recesses. Figure 2 shows a piston 55 at the end of its inwards movement. The pistons are thereafter retracted. A handle 57 is formed at each end with a pivotal projection 58 having an enlarged head 59. Each projection 58 is pushed into its recess and the enlarged head 59 expands the walls thereof to catch the projection, as shown in Figures 3 and 4. The projection 58 is removably retained therein by its enlarged head 59. Owing to the resilience of the material forming the recess, the projection 58 can be removed by the application of moderate force. It will be appreciated that in the cold-forming process described above, the forming pressure should be applied for at least a minimum period of time to ensure the desired permanent deformation of the plastics material. Such period of time is of course readily determined by practical experiment.

Claims: A method of manufacturing a container and handle combination characterised by the combination of steps that a pre-formed container body (50) of flexible, resilient plastics material is subjected to a cold-forming externally applied pressure operation in which the material is permanently deformed and stretched inwardly wherein two oppositely disposed inwardly extending hollow recesses are produced in the side wall of the container body (50) by said externally applied pressure, said recesses being adapted to receive projections (58, 59) on a handle (57) for the container, forming the handle (57) having projections (58) and enlarged heads (59) on the substantially opposite ends, and forcing said enlarged heads (59) into said hollow recesses causing said enlarged heads (59) to expand the walls of said recesses to removably retain said projections (58). A method of forming a container as claimed in Claim 1 characterised by positioning a pair of dies (51) having bores therein internally of said container (50) at substantially diametrically opposite positions on said side walls, and a pair of pistons (55) outside said side walls in alignment with the bores of said dies (51), displacing the plastics material of said side walls into said bores by applying pressure thereto by moving said pistons (55) against the side walls and into said bores so forming said oppositely disposed inwardly extending hollow recesses. A method as claimed in Claim 2 characterised in that the bores of said pair of dies (51) are positioned at substantially right angles to said side walls. A method as claim in Claim 2 or 3 characterised in that during the displacing step the inwardly extending hollow recesses are formed with wall thicknesses less than the thickness of the container side walls. A method as claimed in Claim 2, 3 or 4 characterised by said pair of pistons (55) having convex projections thereon moveable against said side walls and into said bores.

Inventors: BOCK ERIK, BOCK, ERIK
Applicants: BOCK ERIK, BOCK, ERIK
Application year: 1986
Main classification: B29C67
IPC codes: B29C67, B29C57, B29C49, B29C51, B29C43, B29D22