GB2297711A

GB2297711A - Method and apparatus for manufacturing sealing closure and insert

Info

Publication number: GB2297711A
Application number: GB9502430A
Authority: GB
Inventors: Ronald Davis
Original assignee: Robinson and Sons Ltd
Current assignee: Robinson and Sons Ltd
Priority date: 1995-02-08
Filing date: 1995-02-08
Publication date: 1996-08-14
Also published as: GB9502430D0

Abstract

A method of manufacturing a sealing closure which comprises a cap and a sealing insert comprises moulding one of the cap and insert in an injection moulding machine which incorporates a core (2) which is movable, relative to a cavity tool 1, to vary the configuration of the mould cavity. After the one component has been moulded the core (2) is moved to change the configuration of the mould cavity to a shape suitable for moulding the other of the cap and sealing insert, and material is injected into the new cavity to mould the other of the cap and insert. By appropriate design the insert may be moulded first (Figure 2) or the cap may be moulded first (Figure 4).

Description

METHOD AND APPARATUS FOR MANUFACTURE OF A SEALING CLOSURE The present invention relates to a method and apparatus for manufacture of a sealing closure and, more particularly, to a method and apparatus for manufacturing a sealing closure for containers of liquid or semi-liquid products or the like. Closures made according to the preferred embodiment of the invention are particularly suitable for use on containers of carbonated beverages or on vaccum sealed containers e.g. of hot filled food products.

In order to close, in a sealing manner, a container which is pressurized, for example a bottle containing a carbonated beverage, it is known to employ a screw-threaded plastic cap which mates with a corresponding screw-threaded neck on the container, there being provided in the cap an insert of elastic material which sealingly engages the end of the neck to provide a seal between the neck and the cap. Typically, the cap is formed of a polymer such as polypropylene and the insert is provided as a separate wad or washer which is positioned inside the cap or as a coating of a relatively soft material which has been flowed into the inner end of the cap after the cap has been manufactured to form a sealing insert.

It has also been proposed to manufacture closures suitable for bottles of carbonated beverages by two-stage injection moulding techniques whereby, in a first stage, the body of the cap is injection moulded, and in a second stage the sealing insert is injection moulded into the previously formed cap. Such techniques are disclosed, for example, in United Kingdom patent applications GB-A-2277735 and GB-A-2090902.

The present invention relates to improved methods of effecting two-stage injection moulding of a sealing closure.

According to one aspect of the present invention there is provided a method of manufacturing sealing closure which comprises a cap and a sealing insert, the method comprising: a) moulding one of the cap and the sealing insert in an injection moulding machine which incorporates a core moveable to vary the configuration of the mould cavity; b) moving said core to change the configuration of the injection moulding cavity from a first configuration suitable for moulding the said one of the cap and the sealing insert to a second configuration suitable for moulding the other of the cap and the sealing insert; and c) forming the other of the cap and the sealing insert by injecting suitable material into the cavity formed by movement of the core tool.

In one embodiment of the invention the initial configuration of the tooling facilitates injection moulding of the sealing insert and, after moulding of the insert, the core is moved to define a cavity corresponding to the cap and the cap material is injection moulded to cover the insert. In an alternative embodiment, the initial configuration of the tooling facilitates injection moulding of the cap and, after the cap has been moulded, the insert is moved to define a cavity between the moulded cap and the core into which material for the sealing insert is injection moulded.

Preferably, the injection nozzle through which the material for the insert is injected and the injection nozzle through which the material for the cap is injected are both fixed relative to the body of the tool which defines the mould cavity and appropriate passages are provided from the nozzles to the corresponding cavities so that both stages of injection moulding may be carried out without bodily movement of either the cavity tool or the injection nozzles themselves. This arrangement provides significant advantages as compared with the arrangement of GB-A-2277735 in which, between the two moulding stages, the tooling upon which the first stage was moulded must be shifted bodily relative to the injection nozzles so as to present the partially formed closure to a second injection nozzle for forming the second part of the closure.

Preferably, the movement of the core between its first position and its second position is a linear movement. The linear movement may be effected by any suitable means, for example a cam arrangement or a hydraulic or pneumatic cylinder. If a hydraulic or pneumatic cylinder is used for movement of the core, means are preferably provided for locking the core in its forward position during stage (a) of the moulding process.

According to another aspect of the present invention there is provided an injection moulding machine for injection moulding a sealing closure comprising a cap and a sealing insert, the machine comprising: a cavity tool; a core locatable in the cavity tool to define a first cavity; an injection nozzle for injecting moulding material into the first cavity to form one of the cap and the sealing insert; means for moving said core to change the configuration of the first cavity to form a second cavity suitable for moulding the other of the cap and the sealing insert; and a second injection nozzle for injecting moulding material into the second cavity to form the other of the cap and the sealing insert.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 illustrates schematically in longitudinal cross-section a first embodiment of injection moulding machine according to the present invention; Figure 2 illustrates, on an enlarged scale, the cavity region of the embodiment of Figure 1; Figure 3 is a view corresponding to Figure 1 of a second embodiment of the invention; and Figure 4 is a view, on an enlarged scale, of the cavity region of the embodiment of Figure 3.

It should be noted that in each of the Figures the area above the chain-dotted line X illustrates the components with the core in its forward position, corresponding to the first stage of injection moulding whilst the area below the line X illustrates the components with the core in its retracted position corresponding to the second stage of injection moulding.

Referring firstly to Figures 1 and 2 the illustrated injection moulding machine comprises a cavity tool 1 and a core tool 2. The core tool is a sealing sliding fit in a closure member 3 such that, with the components in their illustrated positions a mould cavity 4 is defined by the cavity tool 1, the core tool 2 and the closure member 3. The tooling is designed, in conventional manner, to part along the face 5 to permit removal of moulded components from the tool. The closure member 3 is mounted on a stripper plate 6 which is operable, in a conventional manner, to strip moulded closures from the core tool after the tool has been opened at the end of an injection cycle.

Suitable means (not shown) are provided for moving the core tool 2 relative to the cavity tool 1 to change the configuration of the cavity 4. The extreme limits of the forward and rearward positions of the core tool 2 are illustrated respectively above and below the chain-dotted line X of Figures 1 and 2. In the forward position of the core tool as illustrated above the chaindotted line X the cavity 10 is generally disc-like and is limited, at its radially outer periphery, by the engagement of the leading face 7 of the core tool 2 with a shoulder 8 defined on the cavity tool 1.With the core tool 2 and the cavity tool 1 in this relative position a suitable material for formation of the sealing insert (for example thermo plastic rubber (TPR)) may be injected through a first injection nozzle 9 into the disc like cavity 10 to form what will, eventually, be a sealing insert within the cap portion of the sealing closure. A generally dove-tail section groove 11 may be formed in the leading face 7 of the core tool 2 to ensure that the injected TPR forms an adequate key with the core tool 2 for retraction purposes.

After formation of the sealing insert as described above the core tool 2 is retracted by any suitable means to the position illustrated below the chaindotted line X of Figures 1 and 2. The effect of this move is to define a cavity 12 which is generally cup-shaped and which includes an annular portion 13 defined between the radially outer surface of the core tool 2 and the confronting wall of the cavity tool 1 and a disc-like portion 14 defined between the previously moulded insert 15 and the confronting face 16 of the cavity tool 1. The annular portion 13 and the disc like portion 14 intercommunicate so that the entire cavity is generally cup-shaped. A suitable material for formation of the cap portion of the closure, for example polypropylene, is injected into the cavity 12 via a runner 17 from a second injection nozzle 18.

It will be appreciated from the above description that the only component which moves between moulding of the insert and moulding of the cap is the core tool 2. The remaining components of the tooling, and the injection nozzles, remain fixed relative to the injection moulding machine. Accordingly, difficulties associated with bodily movement of the tooling are eliminated.

After a cap has been formed the mould is opened and the completed cap stripped in conventional manner. It will be noted that the runner 17 is in part defined by opposing faces 19,20 of the stripper plate and the cavity tool holder. With this arrangement the sprue remaining in the runner 17 is automatically stripped from the tooling when the cap is removed. The sprue material may be recycled.

Referring now to Figures 3 and 4 there is illustrated a second embodiment of the invention. In this embodiment the arrangement of the cavity tool 101, injection nozzles 109, and the runner 117 remain substantially the same as in the embodiment illustrated in Figure 1. However, the one-part core tool 2 of Figure 1 has been replaced by a two-part core tool 102 which comprises an outer body 121 and an inner pin 122 which is moveable relative to the body 121 between a forward position as illustrated above the chain-dotted line X and a retracted position as illustrated below the chain-dotted line X.

Referring particularly to Figure 4 it will be noted that in the forward position of the pin 122 a cavity 123 is formed which comprises an annular portion 123A defined between the radially outer surface of the body 102 and the confronting wall of the cavity tool 101 and a disclike portion 123B which is defined between the leading face 124 of the pin 122 and the confronting face 125 of the cavity tool 101. In the centre of the leading face 124 of the pin 122 a raised portion 126 of the pin engages the face 125 of the cavity tool 101. Accordingly, with the pin 122 in its forward position the runner 127 of the injection nozzle 109 is isolated from the cavity 123. With the pin in this position suitable material for formation of the cap portion of the closure is injected via the runner 117 to form the cap portion.

After the cap portion has been moulded utilizing the cavity 123 as described above the pin 122 is retracted to the position illustrated below the chain-dotted line X and thereby forms a disc-like cavity 128 located between the leading face 124 of the pin 122 and the confronting interior surface of the previously moulded cap. Movement of the pin 122 to the retracted position moves the projection 126 out of engagement with the face 125 of the cavity tool and thereby opens the runner 127 to the new cavity 128 allowing suitable material, for example, TPR, to be injected into the cavity 128 to form the sealing insert.

After the second stage of injection moulding the tools are opened along the face 105 and the completed cap is stripped from the tool 102 in conventional manner. As with the embodiments of Figures 1 and 2, separation of the tools and stripping of the cap also results in stripping of the sprue from the runner 117.

The materials from which the cap and insert respectively are moulded may be chosen from a wide range of materials. In the preferred embodiment, the cap is moulded from polypropylene and the insert from thermo plastic rubber. However, any other suitable materials may be used for these components.

Claims

CLAIMS:

1. A method of manufacturing a sealing closure which comprises a cap and a sealing insert, the method comprising: a) moulding one of the cap and the sealing insert in an injection moulding machine which incorporates a core moveable to vary the configuration of the mould cavity; b) moving said core to change the configuration of the injection moulding cavity from a first configuration suitable for moulding the said one of the cap and the sealing insert to a second configuration suitable for moulding the other of the cap and the sealing insert; and

c) forming the other of the cap and the sealing insert by injecting suitable material into the cavity formed by movement of the core tool.

2. A method according to Claim 1 wherein the initial configuration of the tooling facilitates injection moulding of the sealing insert and, after moulding of the insert, the core is moved to define a cavity corresponding to the cap and the cap material is injection moulded to cover the insert.

3. A method according to Claim 1 wherein the initial configuration of the tooling facilitates injection moulding of the cap and, after the cap has been moulded, the insert is moved to define a cavity between the moulded cap and the core into which material for the sealing insert is injection moulded.

4. A method according to any preceding claim wherein the injection nozzle through which the material for the insert is injected and the injection nozzle through which the material for the cap is injected are both fixed relative to the body of the tool which defines the mould cavity and appropriate passages are provided from the nozzles to the corresponding cavities so that both stages of injection moulding may be carried out without bodily movement of either the cavity tool or the injection nozzles themselves.

5. A method according to any preceding claim wherein the movement of the core between its first position and its second position is a linear movement.

6. A method according to Claim 5 wherein the linear movement is effected by a cam arrangement or by a hydraulic or pneumatic cylinder.

7. A method according to Claim 6 wherein the core is locked in its forward position during stage (a) of the moulding process.

8. An injection moulding machine for injection moulding a sealing closure comprising a cap and a sealing insert, the machine comprising: a cavity tool; a core locatable in the cavity tool to define a first cavity; an injection nozzle for injecting moulding material into the first cavity to form one of the cap and the sealing insert; means for moving said core to change the configuration of the first cavity to form a second cavity suitable for moulding the other of the cap and the sealing insert; and a second injection nozzle for injecting moulding material into the second cavity to form the other of the cap and the sealing insert.