GB2218032A

GB2218032A - Injection moulding a hinge

Info

Publication number: GB2218032A
Application number: GB8905449A
Authority: GB
Inventors: Toshiaki Okuyama
Original assignee: KAKOKANAGATA S KK
Current assignee: KAKOKANAGATA S KK
Priority date: 1988-03-16
Filing date: 1989-03-09
Publication date: 1989-11-08
Anticipated expiration: 2009-03-09
Also published as: GB2218032B; JPH01235619A; DE3908479A1; GB8905449D0

Description

9218032 A A- - 1 METHOD OF INJECTION MOULDING A HINGE The present

invention relates to a method of injection-moul ding a hinge and to an injection-moulded hinge.

Hinges manufactured by injection moulding are used to movably connect two parts, particularly to connect a container and lid to be relatively movable. Such hinges may be present in, for example, goods containers, confectionery cases, fountain pen containers, watch containers and compact disc containers.

Generally, these containers are manufactured from thermoplastic resin by injection moulding. In this case, a lid and a container, one of which has a shaft and the other a bearing, are moulded separately and, by tak ing advantage of the resilience of resin, the shaft and bearing are united into a hinge either manually or by machine in order to connect the lid and container together.

However, hinge components assembled by such a method may tend to separate during use if the shaft is an easy fit in the bearing bore, or the components are not accurately connected due to looseness of the hinge. A shaft and bearing, if moulded to be a precise fit, could be damaged during assembly.

There is thus a need for an injection moulding method allowing direct manufacture of a hinge with a shaft already engaged in a bearing and avoiding the drawbacks of the conventional method described above.

Such a method should also permit direct manufacture, in one injection moulding step, of various types of articles with parts movably connect- ed by a hinge.

According to a first aspect of the present invention there is provided a method of injection-moulding a hinge with a hinge shaft in a 2 - bearing bore, the method comprising the steps of providing a mould which has a cavity for a hinge bearing, sliding into the cavity a core element with a cylindrical outer circumferential surface for defin ing the wall of a bore in the bearing and with a recess for defining a hinge Fhaft within the bore, and injecting moulding material into the cavity inclusive of the recess for moulding of said bearing and said shaft within said bearing bore.

Preferably, the core element is a cylindrical slide which has a tip of concave shape and which is inserted into a hinge moulding cavity of the mould, a moulding material being injected into the mould so that the bearing, whose bore wall is defined by the outer surface of the cylinder, is moulded in the region outside the outer cylinder surface and the shaft is'moulded in the inside recess of the concave tip. For preference, the slide is inserted so as to leave a space between the region outside the outer cylinder surface of the slide and the inside recess of concave surface at the inserted tip of slide piece, with the result that the moulding material is moulded to connect the shaft with the bearing by, for example, frangible connection means.

According to a second aspect of the present invention there is provided an injection moulded hinge comprising a hinge shaft engaged in a bore of a bearing of the hinge, the bearing and the shaft being integrally connected by frangible connecting means.

The shaft can be attached to one oart to be united and the bearing attached to another part to be united, and the shaft and bearing interconnected by a thin film in the form of a disk or narrow rods in the form of spokes of wheel, thus extending substantially radially of the shaft.

Examples of the method and embodiments of the hinge of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Figs. 1 (a) to (e) are sectional views of different embodiments of a hinge manufactured by a method exemplify ing the present invention; are sectional views of two forms of hinge mould with inserted core element; are perspective views of three containers with hinges manufactured according to a metho-d exemplifying the invention; is a plan view, with portions broken away for the sake of clarity, of a mould for use in performance of a method exemplifying the invent ion; is a cross-section along the line A-A of Fig. 4; is a cross-section along the line B-B of Fig. 4; and are enlarged sectional details of the mould of Fig. 4 during moulding of a hinge.

Referring now to the drawings, there is shown in Fig. 1 (a) a hinge in which the outer surface of a hinge shaft 20 and the inner surface of a bore in a hinge bearing 21 are connected together by a thin film 30 of disc shape. Fig. 1 (b) shows a hinge in which the outer surface of the shaft 20 and the inner surface of the bore are connected together by narrow rods 31 in the form of spokes of wheel, while Fig. 1 (c) shows a hinge in which the outer surface of the shaft is not connected with the inner surface of the bearing bore. Fig. 1 (d) shows a hinge Fi gs. 2 (A) and (B) Figs. 3 (A) to (C) Fi 9. 4 Fi 9. 5 Fi 9. 6 Fi gs. 7 (A) and (B) 4 in which the shaft 20 is engaged in the bores of two bearings 21, the outer surface of the shaft and the inner surfaces of the bores being connected together in the same manner as in Figs. 1 (a) and 1 (b), whereas Fig. 1 (e) shows a similar hinge in which the outer surface of shaft is not connected with the bore surfaces.

- In the case of hinges in which the outer surface of the shaft and the inner surface of a bearing bore are connected together, the connection means can be broken by turning the shaft by force when use of the hinge is intended to commence. The connection means should be thin or narrow so as to be easily broken by hand.

Although hinges with interconnected shaft and bearing such as those of Figs. 1 (a), (b) and (d) do not actually work as a hinge until the connection means is broken, the term "hinge" in this specification embraces hinges with thehinge components interconnected in this manner.

An injection moulding method exemplifying this invention is illustrat- ed by reference to Figs. 2 (A) and (B), each of which is a sectional view showing a part of a mould with a cylindrical slide piece 12, having a tip with a recess of concave shape, inserted into a hinge moulding cavity formed by a fixed mould half 10 and a movable mould half 11. By means of the inserted slide piece 12, the mould cavity is separated into a shaft mould cavity 13 and a bearing mould cavity 14. Moulding material is t-hen injected from the sides of the shaft and bearing moulding cavities for moulding of a bearing in the region outside the outer cylinder surface of the slide piece 12 and a shaft in the inside of the recess of slide piece 12. Thus a hinge with shaft engaged in a bearing bore is produced.

Other operations from injecting the moulding material to removing 1 i the moulded hinge can be the same as for usual injection moulding methods using a mould for plastics materials.

Depending on the manufacturing method, a hinge with its shaft and bearing separated in the manner shown in Fig. 1 (c) or (e) is produced if the mould halves 10 and 11 contact the tip surface of the slide piece 12 such that the shaft mould cavity 13 and bearing mould cavity 14 are completely separated, as shown in Fig. 2 (A). If the tip surface of the slide piece 12 does not contact the mould halves, but leaves a small gap between this surface and the mould halves, as shown in Fig. 2 (B), moulding material flows into this gap and forms a hinge with the shaft and bearing connected together. Intermediate shapes between Figs. 2 (A) and (B) are possible if, for example, a slide piece 12 with unevenly surfaced tip is used. The cavity 13 is then connected with the cavity 14 through a gap formed at the tip surface so as to pro- vide a hinge with a shaft connected with a bearing in the rod shape shown in Fig. 1 (b) or a hinge with a shaft connected with a bearing in an intermediate shape between Figs. 1 (a) and (b).

The moulding material used is preferably thermoplastic resin, for example styrene resin, methacrylic resin, acrylonitrile-butadiene- styrene resin, acrylonitrile-styrene resin, polycarbonate resin, rigid polyvinyl chloride resin, polyamide resin, polyethylene resin, polypropylene resin or polyacetal resin.

The hinge movably connects two parts to make an article, for example a container with a lid openable and closable by the hinge.

Figs. 3 (A) to (C) show some examples of containers incorporating hinges. Thus, Fig. 3 (A) shows a square container with a hinge of the form of Fig. 1 (a), (b) or (c), namely a single shaft supported by single bearing, Fig. 3 (B) shows a square container with hinge of the form of Fig. 1 (d) or (e), namely a shaft supported by two bearings, and - 6 Fig. 3 (c) shows a cylindrical container with hinge of the form of Fig. 1 (d) or (e).

For production of these containers, there is used a mould in which the shaft mould cavity is linked to a mould cavity for one part of the container and the bearing mould cavity is linked to a mould cavity for another part of the container. The moulding material is injected into the mould cavities of the two container parts, so that container with two parts united by at least one hinge is produced in one injection moulding step.

Preferred embodiments of moulds used in methods exemplifying this invention and methods of manufacturing articles with two parts connected by hinges(s) are illustrated by reference to Figs. 4 to 7.

Fig. 4 shows in plan view a mould for use in injection moulding of the container of Fig. 3 (A). The mould comprises a mould half 10 at the fixed side, a mould half 11 at the movable side and a slide piece 12. Fig. 4 shows a view from the direction of mould half 10. On right side of the line B-B, the mould half 11 is shown with omission of the mould half 10.

Fig. 5 is a section along the line A-A in Fig. 4 and Fig. 6 a section along the line B-B. Figs. 7 (A) and (B) show the hinge moulding region. of the mould, Fig. 7 (A) showing a state with the mould closed and an article being mo51ded and Fig. 7 (B) showing the opened mould after injection moulding. In Fig. 5, the omitted part in Fig. 4 is restored to the original state and a guide pin 15 is shown.

The assembly of the mould is completed by insertion of the slide piece 12 on the mould half 11. The slide piece is guided by the guide pin 15 and between the mould halves 10 and 11 in harmony with movement z i T of the half 11 to unite with the half 10. In the assembled state of the mould, a mould cavity for the container 22 is connected to a bearing mould cavity and a mould cavity for the lid 23 to a shaft mould cavity.

Fig. 6 shows a state in which thermoplastic resin is injected from the side of mould half 10 into the container mould cavity and the lid mould cavity. After injection of the thermoplastic resin, the mould is opened and the moulding is separated from the mould half 11 by an ejector pin 16. Thus the container with lid, of the form shown in Fig. 3 (A), is removed.

A hinge embodying the present invention can be designed to have a structure in which the shaft or bearing has low resilience or which is made of poorly resilient material such that the shaft and bearing cannot be fitted together after moulding. By means of a method exemplify- ing the invention, a hinge with a shaft engaged in a bearing bore can be produced in one injection moulding step. In addition, an article with two parts united by one or more hinges can be manufactured in a single injection moulding step, which represents a reduction in the number of assembly processes and a rationalisation of parts control. Moreover, one possible protective measure against shoplifting is the selling of products stored in containers which are as large as possible. A hinge of a kind produced by the method of the present invention can be effective for this purpose: the main body of a container and lid can be kept open by a hinge with a shaft and bearing connected together by frangible connecting means able to be broken by bending. This arrangement makes it possible to package the product to a larger size when sold. A purchaser of this product subsequently manually bends the lid to break the connected section and thus produces a freely opening and closing container.

Claims

- 8 CLAIMS 1. A method of injection-moulding a hinge with a hinge shaft in

a bearing bore, the method comprising the steps of providing a mould which has a cavity for a hinge bearing, sliding into the cavity a core element with a cylindrical outer circumferential surface for defining the wall of a bore in the bearing and with a recess for defining a hinge shaft within the bore, and injecting moulding material into the cavity inclusive of the recess for moulding of said bearing and said shaft within said bearing bore.
2. A method as claimed in claim 1, wherein the step of sliding comorises so disposing the core element within the cavity that the bearing and shaft when moulded are integrally connected by frangible connecting means.
3. A method as claimed in claim 1 and substantially as hereinbefore described with reference to Fig. 2 A of the accompanying drawings.
4. A method as claimed in claim 1 and substantially as hereinbefore described with reference to Fig. 2 B of the accompanying drawings.
5. An injection moulded hinge comprising a hinge shaft engaged in a bore of a bearing of the hinge, the bearing and the shaft being integrally connected by frangible connecting means.
6. A hinge as claimed in claim 5, the connecting means being in the form of a disc.

0
7. A hinge as claimed in claim 5, the connecting means being in the form of a plurality of rods extending substantially radially of the shaf t.

Y
8. A hinge substantially as hereinbefore described with reference to any one of Figs. 1 (c), 1 (b) and 1 (d) of the accompanying drawings.
9. A hinged article comprising a hinge as claimed in any one of claims 5 to 8, the pin being attached to one part of the article and the bearing to another part of the article.
10. An article as claimed in claim 9 and substantially as hereinbefore described with reference to any one of Figs. 3 (A), 3 (B) and 3 (C) of the accompanying drawings.

Published 1989 at The Patent Office, SW,,e House. 66 71 High Holrx-n. LordonVv-CiR4TP. Further copies maybe obtainedfrom The Patent Office. Sales Branch, St Mary Cray, Orpington, Kent BR-5 3RD. Printed by Mliltiplex techniques ltd, St Mary Cray. Kent, Con. 1/87