MOULDING PLASTICS ARTICLES

Abstract: A plastics article to be moulded has portions such as to obstruct mould release. The use of complex moulding apparatus is avoided by moulding the article with those portions disposed in positions differing from their intended positions, connected to the article by flexible webs. After moulding, the portions are hinged to their final positions, and secured. One application of the invention is the manufacture of a camera filter holder (1), where members (8, 9) with slots (71, 72, 73; 81, 82, 83) for filters, are moulded with the slots at right-angles to the plane of the holder (as shown for member 7) and then hinged through 90` and welded at the final position (as shown for member 8).

Description: "MOULDING PLASTICS ARTICLES" The present invention relates to the moulding of articles of plasticsmaterial. The ease with which articles can be moulded in plastics is heavily dependent on the shape of the article. Often articles are required having apertures, recesses or projections such as to hinder removal of the article from the mould, so that it cannot be formed in a two part mould. With conventional techniques such articles have to be formed in a number of separate parts, or require the use of complex moulding apparatus, for example having retractable sections. Manufacture is therefore difficult and costly. According to one aspect of the present invention there is provided a method of making a plastics article having portions defining apertures and/or recesses therein whose disposition is such as would obstruct mould release if the article were moulded in a two-part mould, comprising moulding the article with one or more of those portions disposed in positions differing from their intended position such that obstruction of mould- release does not occur and each connected to the remainder of the article by a flexible web, hinging said one or more portions into its/their intended positions, and securing it/them fast to the remainder of the article. In another aspect, the invention provides a 0-..PI method of making a camera filter holder having a generall planar body portion with a central aperture therein, and a pair of members disposed on opposing sides of the aperture and each having therein at least one slot, lying generally parallel to the plane of the body portion for receiving a filter, comprising the steps of moulding the members and body portion from plastics material as a single unit with the members connected to the body porti by flexible webs and disposed with the slots lying in planes generally perpendicular to the plane of the body- portion, hinging the members relative to the body portion so that the slots lie generally parallel to the plane thereof, and securing the members fast to the body portion. The moulding may for example be by injection moulding. Preferably the step of securing the members is effected using ultrasonic welding, although other means, such as the use of an adhesive, may be employed. In a further aspect, the invention extends to articles produced using the above-described methods. An exemplary embodiment of the invention will now be described with reference to the accompanying drawings, in which :- Figure 1 is a front elevation of a camera filter holder; Figure 2 is a side elevation of the holder of figure 1; Figure 3 is a cross-section on line III-III f figure 1; and c: Figure .4 shows -an adaptor ring for mounting the .• holder of figure 1. A camera filter holder 1 comprises a generally planar body portion 2 having a central opening 3. Its rear face is provided with reinforcing ribs 4 and also four projecting fingers 5, with grooves 6 therein, which serve to clip the holder onto an adaptor ring (described below) so that, in use, the opening " 3 lies in front of the camera lens. Secured to the body portion at each side of the holder is a member 7 and 8 having (for example) three slots 71, 72, 73; 81, 82, 83 formed therein. In the finished holder the slots lie generally parallel to the plane of the body portion 2, so that upto three square (or rectangular) filters can be slid into a pair of opposed slots (e.g.72, 82) -One end of _each.member 7,8 -is tapered to facilitate filter insertion, and spring leaves 9 are provided at the base of each slot in order to retain the filter in position. The entire assembly is integrally moulded from a suitable plastics material, e.g. by injection moulding. It will be observed that the member 7 of the holder is shown in figures 1 and 2 in an "opened-out" position, with the slots 71, 72, 73 disposed at right angles to the plane of the body portion 2. The holder is moulded with both members 7, 8 in this position - attached to the body portion only by a relatively thin web or hinge 10. This permits the unit to be made in a straightforward split mould. After moulding, the members 7, 8 are hinged through 90 as indicated for member 7 in figure 2, and secure in position,as-i-ilustrated in figure 3. The eπbers can be fixed by an adhesive, or other convenient means, but in the preferred embodiment ultrasonic welding is employed, and for this purpose staking ribs 11 are formed during moulding. Obviously where this method is employed the assembly must be of a plastics material capable of being ultra- sonically welded. Unfilled polyacetal is found to be suitable. It will be appreciated that this technique considerably simplifies manufacture of the article which, by conventional techniques would of necessity involve complex and costly moulding techniques. The adaptor ring 50 is shown in figure 4 and has an internal thread (not shown) to permit it to be screwed onto the lens assembly of the camera, and an external circumferential rib 51. The holder is retained on the ring by means of the fingers 5 which clip over the ring 10, the rib 51 engaging in the grooves 6. It will be appreciated that the use of the adaptor ring permits the holder to be fitted to different types of camera simply by changing the adaptor ring for one having an appropriate thread: also rotation of the holder relative to the camera is.permitted, which is useful, for example,when employing polarised filters. ^ o:

Claims: CLAIMS : 1. A method of making a plastics article having portions defining apertures and/or recesses therein whose disposition is such as would obstruct mould release if the article were moulded in a two-part mould, comprising moulding the article with one or more of those portions disposed in positions differing from their intended position such that obstruction of mould release does not occur and each connected to the remainder of the article by a flexible web, hinging said one or more portions into its/their intended positions, and securing it/them fast to the remainder of the article. 2. A method according to claim 1 in which the article is moulded in a two-part mould. 3. A method according .to claim 1 or 2 in which the -article is moulded by injection moulding. 4. A method according to claim 1,2 or 3 in which the members are secured to the body by ultrasonic welding. 5. A method of making a camera filter holder having a generally planar body portion with a central aperture therein, and a pair of members disposed on opposing sides of the aperture and each having therein at least one slot lying generally parallel to the plane of the body portion for receiving a filter, comprising the steps of moulding the members and body portion from plastics material as a single unit with the members connected to the. body portion by flexible webs and disposed with the slots lying in planes generally perpendicular to the plane of the body portion, hinging the members. relative to the body portion so that the slots lie generally parallel to the plane thereof, and securing the members fast to the body portion. 6. A method ■ according to claim 5 in which a longitudinally extending spring leaf is integrally formed in the base of each slot. 7. A method according to claim .5 or 6 in which the article is moulded in a two-part mould. 8. A method according to claim 5,6 or 7 in which the article is moulded by injection moulding. 9. A method according to any one of claims 5 to 8 in which the members are secured to the body by ultrasonic welding. 10. An article made by the method according to any one of the preceding claims.

Inventors: DOWNEY D
Applicants: DOWNEY D, DOWNEY PLASTICS LTD
Application year: 1980
Main classification: B29C17
IPC codes: B29C33, B29C45, B29C53, B29C65, B29C69, G03B11