Although the layout of multicavity molds is a geometrically balanced design, when the melt flows into the runner, the shear-induced partial changes in material properties will result in intracavity imbalance. This study placed a rectangular flow restrictor within the tertiary runner of a precision optical lens mold to create melt turbulence through flow blocking. Due to polymer rheological characteristics, uniform melt temperature distribution in the runner channel could be obtained, making the temperature distribution inside the cavity more uniform, and reducing the thermal residual stress and warpage of injection molded parts. The optimal runner restrictor design is placing 5 mm away from the secondary runner centerline, making both the depth and the width of the block 3 mm. A relatively uniform melt temperature distribution with a maximum temperature difference of 1.1 C can be achieved. Injection molds were fabricated according to the optimized restrictor design, and experimental verification was performed. The contour accuracy of a lens parallel to injection direction was improved from 10.44 to 5.03 μm. Therefore, this runner restrictor design can be applied to high-precision optical molds due to the ease of machining and the capability of improving the quality of optical lens.
This was all the more true for the apparatus claims of the second and third auxiliary requests, which were limited further by providing more details on the design of the runner system and by specifying the flow fronts to meet in the haptic cavities only. The taper of the injection gates defined in claim 1 of the third auxiliary request was clearly not obvious in view of document D2, where any weakness or predetermined breaking point between the haptic cavity and the lens had to be avoided.
Runner and Gating Design Handbook.pdf
Document D2 could be considered a suitable starting point for assessing the inventive merits of claim 1 of the first and second auxiliary requests, which structurally differed from document D2 in the provision of first and second sub-runners designed for the first and second flow fronts to meet in the one or more haptic cavities (only). The technical effect of these features was described at column 2, lines 27 to 32 and at column 7, lines 46 to 48 of the patent specification as providing a method and an apparatus for injection moulding an intraocular lens that avoided undesirable optical characteristics by having flow fronts that met in the haptic cavities. It was already known from handbook D11, page 301, middle column, to provide several sub-runners for injecting the material into the mould. According to document D11, their configuration influenced where knit lines were created due to the meeting of flow fronts. These locations were known to have a different molecular orientation which caused undesirable optical characteristics. The layout of the runner system belonged to the common general knowledge of a moulding engineer who could rely on computer programs to optimise the mould filling process. Hence, providing the mould of document D2 with first and second sub-runners in order to locate the knit lines not in the optical cavities but in the first and second haptic cavities was obvious in view of the common general knowledge as set out for example in handbook D11. The subject-matter of claim 1 of the first and second auxiliary requests was thus not based on an inventive step.
Taking account of the teaching of handbook E5, the solution to the second partial problem could equally not render the claimed subject-matter inventive: on page 185, point 2 it was set out that tapering gates (referred to as "pinpoint gates") were generally known and provided for if a close, easy and smooth break-off of the runner from the moulded part was required. This gate design and its advantages thus formed part of the common general knowledge of a person skilled in that art.
2.4 Turning to the solution proposed in claim 1 of the first auxiliary request, reference is made to handbook D11, page 301, middle column, which exemplifies the common general knowledge of a person skilled in the art of designing injection moulds. According to document D11, it is common practice to provide several (sub-)runners for injecting the material into the mould. Their configuration determines where knit lines are created due to the meeting of the flow fronts. These locations are known to have a different molecular orientation, which causes not only mechanical weakness but also undesirable optical characteristics. The layout of the runner system belongs to the common general knowledge of a moulding engineer who could rely on computer programs to optimise the mould filling process. Hence, providing a mould for producing an intraocular lens with first and second sub-runners in order to locate the knit lines not in the optical cavities but in the first and second haptic cavities has to be considered an obvious possibility in view of the common general knowledge as set out in handbook D11. The subject-matter of claim 1 of the first auxiliary request is not based on an inventive step, Article 56 EPC 1973.
Taking into account the teaching of handbook E5, the solution to the second partial problem is equally not capable of rendering the claimed subject-matter inventive: according to page 185, point 2 of document E5, tapering gates (referred to as "pinpoint gates") are generally known and provided for if an easy, smooth and close break-off of the runner from the moulded part is required. This gate design as well as its advantages thus form part of the common general knowledge of a person skilled in that art.
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