AU2002328686A1 - Compressive injection moulding system - Google Patents
Compressive injection moulding system Download PDFInfo
- Publication number
- AU2002328686A1 AU2002328686A1 AU2002328686A AU2002328686A AU2002328686A1 AU 2002328686 A1 AU2002328686 A1 AU 2002328686A1 AU 2002328686 A AU2002328686 A AU 2002328686A AU 2002328686 A AU2002328686 A AU 2002328686A AU 2002328686 A1 AU2002328686 A1 AU 2002328686A1
- Authority
- AU
- Australia
- Prior art keywords
- mould
- thermoplastic material
- injection moulding
- sprue
- compressive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000001746 injection moulding Methods 0.000 title claims description 17
- 239000012815 thermoplastic material Substances 0.000 claims description 35
- 208000015943 Coeliac disease Diseases 0.000 claims description 25
- 230000006835 compression Effects 0.000 claims description 17
- 238000007906 compression Methods 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 9
- 238000002347 injection Methods 0.000 claims description 8
- 239000007924 injection Substances 0.000 claims description 8
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 238000004891 communication Methods 0.000 claims description 3
- 230000000295 complement effect Effects 0.000 claims description 3
- 239000012530 fluid Substances 0.000 claims description 2
- 238000000465 moulding Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229920000515 polycarbonate Polymers 0.000 description 3
- 239000004417 polycarbonate Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 2
- 238000009595 pap smear Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 1
- 239000012768 molten material Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
- B29C45/56—Means for plasticising or homogenising the moulding material or forcing it into the mould using mould parts movable during or after injection, e.g. injection-compression moulding
- B29C45/561—Injection-compression moulding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
- B29C45/56—Means for plasticising or homogenising the moulding material or forcing it into the mould using mould parts movable during or after injection, e.g. injection-compression moulding
- B29C45/561—Injection-compression moulding
- B29C2045/564—Compression drive means acting independently from the mould closing and clamping means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/26—Moulds
- B29C45/27—Sprue channels ; Runner channels or runner nozzles
- B29C45/2701—Details not specific to hot or cold runner channels
- B29C45/2703—Means for controlling the runner flow, e.g. runner switches, adjustable runners or gates
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Description
COMPRESSIVE INJECTION MOULDING SYSTEM The present invention relates to a compressive injection moulding system and associated apparatus and in particular a compressive injection moulding system which utilises the pressure in the injection manifold or sprue to compress or close the mould cavity during the injection process. There are difficulties associated with conventional injection moulding equipment when it is required to mould a thermoplastic article which is very thin. Such thin articles may comprise contact lenses or particularly very thin lenses utilised in equipment such as pap smear testing apparatus. Where the article being moulded is of a thickness of less than 0.25 millimetres there is difficulty in flowing thermoplastic material into the mould. This difficulty occurs due to the fact that injected thermoplastic material, such as polycarbonate, will not flow properly through such narrow cavities but rather starts to roll causing air bubbles and possibly cessational flow altogether. Compressive injection moulding may alleviate such problems to some extent. Compressive injection moulding is a process whereby thermoplastic material is not flowed into a cavity of fixed dimensions but 2 rather the mould cavity is charged with thermoplastic material and then the mould cavity is compressed and reduced in dimension during the charging and/or immediately thereafter. In this manner the cavity into which the thermoplastic material is flowed is originally of sufficiently large a dimension to permit adequate flow but before the flowed-in material is set the mould cavity is reduced in dimension to the required dimension for the finished article. This process requires mechanical rams or other devices in order to close the mould from its expanded position whereat the thermoplastic material is flowed-in to its compressed position. More importantly this compression apparatus must be controlled with respect to the timing of closure and the rate of closure in order that a satisfactory finished article may be produced. To date there have been difficulties synchronising the timing of the closing of the mould (and the rate of closure) with the injection of thermoplastic material through the sprue such that satisfactory moulding of articles such as polycarbonate lenses of less than 0.25 millimetres has either not been possible or has only been possible with extremely expensive and elaborate equipment. Accordingly it is an object of the present invention to ameliorate one or more of the disadvantages with existing compressive injection moulding equipment or at least to provide the market with an alternative.
3 According to the present invention there is disclosed compressive injection moulding equipment comprising a main sprue for channelling molten thermoplastic material into a compression type mould adapted to reduce the dimensions of the mould cavity during the injection process; a secondary sprue and runner system in fluid communication with the main sprue adapted to divert thermoplastic material to a position whereat it may directly or indirectly urge a component of the mould towards a complementary mould component thereby reducing the cavilty dimensions; means to control the flow of thermoplastic material in the main and secondary sprue so as to control the timing and rate of mould closure with respect the timing and rate of injection of thermoplastic material into the mould cavity. One embodiment of the present invention will now be described with reference to the accompanying drawing in which: Figure 1 is a sectional schematic view of part of a mould and sprue runner system in accordance with the present invention. According to the embodiment of Figure 1 there is depicted a mould cavity 1 of a shape appropriate for forming a lens and defined by upper and lower mould components (not shown). It will be observed that the mould cavity 1 is in communication with a main sprue runner 2 fed by main sprue inlet 3 through which molten polycarbonate material (not shown) is injected.
4 The main sprue runner system 2 is linked at position 4 via a secondary sprue 5 to a secondary runner system 6 adapted to flow thermoplastic material. A flow restrictor/controller is provided at 7 in order to control the timing for and volume of injection of thermoplastic material into cavity 1. A further flow restrictor 8 is provided in the secondary sprue runner 6 in order to control the flow of thermoplastic material from first end 9 of secondary runner system 6 to the second end 10 of secondary runner system 6. The purpose of admitting molten thermoplastic material to the second end 10 of secondary runner system 6 is to urge compression piston 11 upwardly thereby urging the lower mould component (not shown) against the upper mould component (not shown) with the upper mould component being controlled by cavity piston 12. This urging of the lower mould component against the upper mould component reduces the thickness of cavity 1. In use the main sprue is pressurised hence causing thermoplastic material to be injected into cavity 1 via flow restrictor 7 on the main runner system. At this moment the upper and lower mould components are positioned to define the mould cavity 1 at a volume corresponding to the 5 maximum which is permitted by the stroke of the compression piston and which will admit thermoplastic material to the cavity in such a manner as to promote good flow through the cavity. At the same time this pressurising of the main sprue will pressurise the secondary sprue and cause thermoplastic material at the second end 10 of the secondary runner system 6 to be urged against the bottom of compression piston 11 hence moving it and the attached lower mould component upwardly against the upper mould component (not shown) thereby causing cavity 1 to be progressively reduced in dimension to the minimum volume position defined by the maximum extent of the upward stroke of the compression piston. During the reduction in size of the cavity 1 the thermoplastic material which has been or is being flowed into the cavity via flow restrictor 7 is urged throughout the cavity and compelled to adopt the dimensions desired for the finished product. Adjustable pressure relief mechanisms 14 are provided in the secondary runner system so as to assist in regulating the speed and timing of the compression stroke of the compression piston. It will be appreciated that in order that the compression piston be capable of urging the lower mould component upwardly against the pressure of thermoplastic material in cavity 1 the area of that piston against which the molten thermoplastic material must act should be greater than the 6 area of molten material against which the lower mould component is acting and in this regard test units have used a ratio of 16.4:1. A component ejector 15 is also provided as is the case with conventional compressive moulding equipment and it will be observed that this component ejector operates through the hollow core 16 of compression piston 11. It has been found that compressive injection moulding equipment in accordance with the present invention and utilised in accordance with the methods as above described facilitate the moulding of lenses such as lenses used in the course of pap smear tests having a thickness of 0.22 millimetres or less. Testing has shown that the moulding of lenses down to 0.13 millimetres can be reliably performed and indeed if uses can be found for articles down to approximately 0.05 millimetres in thickness it is expected that apparatus and methods in accordance with the present invention will be capable of reliably producing such articles. It should be appreciated that alternative embodiments of the present invention may be devised apart from those above described without departing from scope and intendment of the present invention and it is the intention of the present document to cover such embodiments.
Claims (7)
1. Compressive injection moulding equipment comprising a main sprue for channelling molten thermoplastic material into a compression type mould adapted to reduce the dimensions of the mould cavity during the injection process; a secondary sprue and runner system in fluid communication with the main sprue adapted to divert thermoplastic material to a position whereat it may directly or indirectly urge a component of the mould towards a complementary mould component thereby reducing the cavity dimensions; flow restrictors and/or controllers to control the flow of thermoplastic material in the secondary sprue thereby regulating the timing and rate of mould closure by reference to the pressure of thermoplastic material in the main sprue.
2. Compressive injection moulding equipment in accordance with claim 1 hereof wherein the thermoplastic material in the secondary sprue acts on the mould via a compression piston.
3. Compressive injection moulding equipment in accordance with claim two hereof wherein at the commencement of the injection process upon pressurisation of thermoplastic material in the main sprue the components of the mould cavity are biased to an open position corresponding to the maximum stroke of the compression piston whereat the mould cavity is at a maximum volume thereby permitting admission of thermoplastic material through the mould cavity whilst maintaining good flow characteristics. 8
4. Compressive injection moulding equipment in accordance with claim 2 hereof wherein there are provided one or more adjustable pressure relief valves in the secondary sprue system to facilitate regulating the speed and timing of the compression stroke of the compression piston.
5. Compressive injection moulding equipment in accordance with claim two hereof wherein the area of the compression piston acted upon by the thermoplastic material in the secondary sprue is of a ratio exceeding 10:1 as compared with the area of thermoplastic material in contact with the mould component being moved by the piston.
6. Compressive injection moulding equipment in accordance with claim two hereof wherein the area of the compression piston acted upon by the thermoplastic material in the secondary sprue is of a ratio between 14:1 and 18:1 as compared with the area of thermoplastic material in contact with that the mould component being moved by the piston.
7. A method of compressive injection moulding wherein part of the pressurised thermoplastic material intended to fill a mould is diverted to a position whereat it may directly or indirectly urge a component of the mould towards a complementary mould component thereby reducing the mould cavity dimensions during filling of the mould cavity whilst flow restrictors and/or controllers control the flow of diverted thermoplastic material thereby regulating the timing and rate of mould closure by reference to the pressure of the main body of thermoplastic material being injected into the mould cavity.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/AU2002/001357 WO2004033183A1 (en) | 2002-10-08 | 2002-10-08 | Compressive injection moulding system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| AU2002328686A1 true AU2002328686A1 (en) | 2004-05-04 |
Family
ID=32075009
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU2002328686A Abandoned AU2002328686A1 (en) | 2002-10-08 | 2002-10-08 | Compressive injection moulding system |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU2002328686A1 (en) |
| WO (1) | WO2004033183A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110893692A (en) * | 2018-09-13 | 2020-03-20 | 德斯马制鞋设备有限公司 | Injection molding system with pressure dependent valve |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0584784A (en) * | 1991-09-27 | 1993-04-06 | Yoshida Kogyo Kk <Ykk> | Injection mold having compression mechanism built therein |
-
2002
- 2002-10-08 AU AU2002328686A patent/AU2002328686A1/en not_active Abandoned
- 2002-10-08 WO PCT/AU2002/001357 patent/WO2004033183A1/en not_active Application Discontinuation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110893692A (en) * | 2018-09-13 | 2020-03-20 | 德斯马制鞋设备有限公司 | Injection molding system with pressure dependent valve |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2004033183A1 (en) | 2004-04-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MK6 | Application lapsed section 142(2)(f)/reg. 8.3(3) - pct applic. not entering national phase | ||
| NB | Applications allowed - extensions of time section 223(2) |
Free format text: THE TIME IN WHICH TO ENTER THE NATIONAL PHASE HAS BEEN EXTENDED TO 08 JUN 2005. |
|
| MK1 | Application lapsed section 142(2)(a) - no request for examination in relevant period |