GB2315736A

GB2315736A - Boxes and cases

Info

Publication number: GB2315736A
Application number: GB9616209A
Authority: GB
Inventors: David Lane
Original assignee: CP MEGA Ltd
Current assignee: CP MEGA Ltd
Priority date: 1996-08-01
Filing date: 1996-08-01
Publication date: 1998-02-11
Also published as: GB9616209D0

Abstract

In a method of making a box or a case, lengths of aluminium corresponding to the sides of the box or case are mitred at the corners. The aluminium has a cross-section slotted to tightly engage an insert 9. The lengths are joined by forcing them on to L-shaped inserts 9 to form a rectangular frame which is then attached to the open top of a box shell.

Description

ImDrovements relating to boxes and cases The invention relates to the manufacture of boxes and cases.

The bodies and lids of rectangular cases are of box form and may be made of any of a variety of suitable materials, for example of fibre board, plastic, plywood or ruggedised aluminium. The lid and body are usually provided with a metal rim to which hinges, clasps or locks may be attached. Open-top boxes may similarly be given a metal rim for rigidity and protection from damage. The metal of choice for the rim is aluminium, which term herein is to be taken to include alloys consisting mainly of aluminium. Aluminium is particularly suitable for this purpose, as it is readily available in suitable lengths of almost any desired cross-section, is of good appearance and is easily worked.

If the lengths of aluminium are simply cut to form a mitre at the corners a problem arises during use. No matter how accurately the mitres are initially formed, stresses in use will cause the case to become slightly deformed, the abutting edges at the mitres will become mis-aligned, and a sharp edge will be exposed which may cause damage or injury.

In an attempt to overcome this problem an alternative method makes use of a single length of aluminium corresponding to the perimeter of the case and having V-shaped notches of 900 apical angle where the mitres are to be formed. The aluminium is bent to form the rim, the ends abutting in the middle of a side. The notches penetrate slightly short of the full width of the aluminium, so that when the rim is bent to shape a rounded edge of thin metal is presented at the outside of the mitre.

However, even with this construction a problem still arises in use. Aluminium and its alloys, as is well known, work harden under deformation, and the stresses induced in handling cause the thin metal at the outside of the mitres to be repeatedly slightly deformed, so that the metal hardens and becomes brittle and even tually fractures, leaving a sharp and jagged edge which again is liable to cause damage or injury.

It is an object of the present invention, which is defined in the appended claims, to provide an improved method of constructing cases and boxes which avoids this problem.

The invention will be further explained with reference to the accompanying drawings, in which Figure 1 is an end view of a length of aluminium alloy extrusion for use in the invention, Figure 2 illustrates the method of assembly of a mitre joint, Figure 3 illustrates the completed joint of figure 2, and Figure 4 is a section. taken close to a corner joint, of a case and lid employing extrusions of alternative cross section.

Figure 1 shows, in end view, an aluminium alloy extrusion 1 designed to form the rim of the body of a case. The extrusion is of generally U-shape, adapted to receive the outer wall of the box constituting the case body, which in this example is of relatively thick material, such as moulded plastic or thick plywood. The lid of the case is also in the form of a shallow box likewise with an aluminium rim. This lid rim, (not shown) is similar, except for the lip surface, which is shaped to mate with the lip of the case body rim.

Externally the outer and inner sides 2,3 of the rim may be plain or may be grooved to give an ornamental finish. The edge surface 4 is shaped to mate with the rim of the case lid when the case is assembled. The internal surfaces of the side walls are smooth and parallel for most of their depth and spaced apart by the thickness of the material forming the case body. Beyond this parallel region the side walls are internally grooved at 7 and 8 to receive and grip tightly a sheet metal insert 9, as will be described below with reference to Figure 2.

The assembly of the case will now be described. The aluminium extrusion 1 is first formed into a frame to fit the case body.

For this purpose the material is cut to the required dimensions, the ends being cut at an angle of 450 to form mitred joints at the corners. The cut lengths are then joined to form a rectangular frame by forcing them on to L-shaped inserts 9 of sheet steel, the inserts 9 entering the grooves 7,8 and being tightly gripped, giving a secure mitre joint, the external appearance of which is shown in Figure 3. The internal walls of the rim are then coated with adhesive and attached to the edge of the case body.

The lid of the case is formed in an exactly similar manner, except that the lip of the rim is shaped to mate with that of the body.

The case is then completed by the addition of hinges, locks and handles, as required.

Figure 4 illustrates a modified form of construction suitable where the case body is of thinner material, for instance ruggedised aluminium sheet. The figure shows a fragmentary section taken through the mating edges of the case and lid at a position adjacent to a mitre joint.

In this construction the extrusion 1 is of approximately L-shaped cross-section, the shorter arm of the L being formed with the grooves 7,8 to receive the sheet metal inserts 9. The rim frames are first assembled by forcing the cut lengths of aluminium on the metal inserts, as before, and then the rims are attached to the case body and lid, this time by rivets 10 passing through the longer arm of the L. The case rim has a projecting ridge 11 which enters a corresponding recess 12 in the lid rim to form a substantially weathertight seal.

Claims

1. A box comprising an open-topped shell of rectangular outline with an aluminium rim cut to form a mitre at each corner, in which the interior of the rim is provided with slots dimensioned so as to tightly engage an L-shaped rigid insert force-fitted into adjacent rim sections at each corner to hold them in position.

2. A box according to claim 1 or claim 2 in which the insert is of steel.

3. A case having a body and a lid each according to claim 1 or claim 2 hinged together by hinges attached to their rims.

4. A method of making a box according to claim 1 or claim 2 comprising cutting lengths of aluminium mitred at the corners, corresponding in lengths to the sides of the box and having a cross-section slotted to tightly engage an insert, forcing the aluminium lengths on to L-shaped inserts to form a rectangular frame, and attaching the frame to the open top of a box shell.