Injection molds including vertical snap-gate devices and methods for producing molded articles using the same

Disclosed are injection molds, injected molded articles, and methods for using the same. The injected molds include a mold cavity and an injection molding conduit having a first end, a second end defining an outlet in fluid communication with the mold cavity, a first interior transverse dimension that is perpendicular to a longitudinal axis of the injection molding conduit, a second interior transverse dimension that is perpendicular to the longitudinal axis and to the first interior transverse dimension, and at the second end, the second interior transverse dimension is at least three times larger than the first interior transverse dimension, and the second interior transverse dimension of the injection molding conduit is substantially aligned with a thickness of a portion of the mold cavity that is adjacent to the outlet of the injection molding conduit.

BACKGROUND

A. Field of the Invention

The present invention relates generally to injection molding, and more specifically, but not by way of limitation, to injection molds and an injected molded article for ophthalmic lenses including vertical snap-gate devices and methods for producing molded articles using the same.

B. Description of Related Art

Injection molding is a technology commonly used for high-volume manufacturing of parts made from, most commonly, thermoplastic polymers. During an injection molding process, a solid plastic resin is introduced to an injection molding machine that melts the resin under heat, pressure, and shear. The molten resin is then injected into a mold cavity having a particular shape. The injected plastic is held under pressure in the mold cavity and is cooled until the injected plastic forms a solidified part having a shape that essentially duplicates the shape of the mold cavity. The cooled part can then be ejected from the mold along with hardened gate(s) and runner(s) that supplied the molten resin into the mold cavity. Injection molded parts often show evidence of the injection molding process by including gate(s), parting line(s), flash, and/or the like. Frequently, such parts require post-ejection processing in order to remove such gate(s), parting line(s), flash, and/or the like for functional and/or aesthetic purposes.

Injection molded parts often show evidence of the injection molding process including the presence of parting lines, sprues, gates, and ejector pin marks on the final part. Frequently, molded parts require the gate and runner systems and other appendages to be mechanically removed after ejection for functional and/or aesthetic purposes. Traditionally, injection molded ophthalmic lenses are prepared with thin gates that are typically either fanned wide and flat or fanned large in both directions. These gate appendages are often thinner than the part edge, can bend during ejection, and require further clipping and trimming. Addressing these deficiencies for injection molding of ophthalmic lenses would increase the overall efficiency of the process.

The documents JP H01 156 019 describes for instance a method capable of rapidly breaking and separating a molded product from a molding finished article without using an edge tool or laser beam. The documents US 2006/093700 describes an optical component molding apparatus for simultaneously producing a plurality of optical components.

SUMMARY

Some embodiments of the present injection molds and injected molded articles, at least via including a vertical snap-gate device, provide solutions to problems associated with injection molding of ophthalmic lenses. In particular, a vertical snap-gate is provided that is robust enough for lens ejection and manipulation, and permits appendage-free de-gating that mitigates further post ejection lens processing. In addition, the vertical snap-gate can reduce the need for post-ejection part processing (e.g., edging, cutting, cleaning, finishing, removal of gate(s), parting line(s), flash, and/or the like), thereby increasing the efficiency of the injection molding process, providing for injection molded parts with increased function and/or improved aesthetics, and/or the like.

In some embodiments of the present injection molds, a clean ejection molding part edge can be provided after gate removal, post processing of the part edge such as mechanical gate cutting and/or edging to remove remaining appendages can be reduced or eliminated, and/or the injection molding part can be ejected without gate deformation due to a thin gate cross-section.

In some embodiments of the present injection molds, the longitudinal axis of the snap-gate can be parallel to the ejection axis of the injection mold, resulting in increased rigidity, allowing for the gate to be bent perpendicular to a direction of the fracture, and resulting in a clean de-gating. The snap-gate device can also provide a hanging tab useful for post molding manipulation, such as for applying hard coatings. The snap-gate can be provided with angled side jets that allow for increased turbulence and mixing of the molten molding material prior to injection into the mold which prevents lens defects caused by flow and filling through the gate. The snap-gate device can also reduce scrap molding material.

Especially, the injection molds according to the invention comprise: a mold cavity, and an injection molding conduit having a first end, a second end defining an outlet in fluid communication with the mold cavity, a first interior transverse dimension that is perpendicular to a longitudinal axis of the injection molding conduit, and a second interior transverse dimension that is perpendicular to the longitudinal axis and to the first interior transverse dimension wherein, at the second end, the second interior transverse dimension is at least two times larger than the first interior transverse dimension;wherein the second interior transverse dimension of the injection molding conduit is substantially aligned with a thickness of a portion of the mold cavity that is adjacent to the outlet of the injection molding conduit and comprising:first and second cavities extending from opposing sides of and in fluid communication with the injection molding conduit;wherein each of the cavities is defined in part by a surface that extends between the injection molding conduit and a periphery of the cavity;wherein, for each of the cavities:the surface is angularly disposed at a non-perpendicular angle relative to a plane that is aligned with the longitudinal axis of the injection molding conduit and bisects the injection molding conduit; and/ora line that extends along the surface in a direction from the first end of the injection molding conduit and toward the second end of the injection molding conduit is angularly disposed at a non-perpendicular angle relative to the longitudinal axis.

In some embodiments, at the second end the second interior transverse dimension is at least two to six times larger than the first interior transverse dimension.

In some embodiments, two or more mold portions that are movable relative to one another between an open state and a closed state in which the mold portions cooperate to define the mold cavity. In some embodiments, the second interior transverse dimension is substantially aligned with a direction in which the mold portions move relative to one another between the open state and the closed state.

In some embodiments, the second interior transverse dimension is larger than a thickness of a portion of the mold cavity that is adjacent to the outlet of the injection molding conduit.

In some embodiments, the second interior transverse dimension is between approximately 110% and approximately 200% of a thickness of a portion of the mold cavity that is adjacent to the outlet of the injection molding conduit.

In some embodiments, the first interior transverse dimension decreases along the injection molding conduit in a direction from the first end and toward the second end. In some embodiments, the second interior transverse dimension increases along the injection molding conduit in a direction from the first end and toward the second end.

In some embodiments, each of the cavities has a thickness that tapers toward the second end of the injection molding conduit.

In some embodiments, each of the cavities is spaced from the outlet of the injection molding conduit in a direction aligned with the longitudinal axis of the injection molding conduit and by a distance that is approximately 0.5 or more millimeters (mm).

The present invention also relates to an injected molded article comprising: a product, a runner, and a gate having first end coupled to the runner and a second end coupled to the product. In particular, the second end of the gate comprises: a first transverse dimension that is perpendicular to a longitudinal axis of the gate, and a second transverse dimension that is perpendicular to the longitudinal axis and to the first transverse dimension. Especially, the second transverse dimension is at least two times or at least six times larger than the first transverse dimension. In particular, the second transverse dimension is substantially aligned with a thickness of a portion of the product that is adjacent to the second end of the gate. According to the invention, first and second tabs extend from opposing sides of the gate. In particular, each of the tabs is defined in part by a surface that extends between the gate and a periphery of the tab. Especially, for each of the tabs: the surface is angularly disposed at a non-perpendicular angle relative to a plane that is aligned with the longitudinal axis of the gate and bisects the gate, and/or a line that extends along the surface in a direction from the first end of the gate and toward the second end of the gate is angularly disposed at a non-perpendicular angle relative to the longitudinal axis.

In some embodiments of the present injected molded article, the second end of the gate extends beyond a portion of the product that is adjacent to the second end in a direction that is aligned with the second transverse dimension.

In some embodiments of the present injected molded article, the second transverse dimension is between approximately 110% and approximately 200% of a thickness of a portion of the product that is adjacent to the second end of the gate.

In some embodiments of the present injected molded article, the product comprises an ophthalmic lens.

Some embodiments of the present methods for producing an injected molded article using the injection mold comprise: injecting injection molding material through the injection molding conduit and into the mold cavity.

Some details associated with the embodiments described above and others are described below.

DETAILED DESCRIPTION

A preferred embodiment of the invention is illustrated inFIG. 1, which shows a perspective view of an injection mold10. Injection mold10can include two or more mold portions (not shown in the figure) that define a mold cavity20. At least one of the mold portions of injection mold10can be moved relative to at least one other of the mold portions between an open state and a closed state. Injection mold10has an injection molding conduit which can include a runner portion40and a gate portion30, where, when an injection molded article is formed within injection mold10, the runner portion40forms at least a portion of a runner of the molded article, and the gate portion30forms at least a portion of a gate of the molded article.

The injection molding conduit is configured to convey injection molding material via the runner portion40and the gate portion30into the mold cavity20of the injection mold10. The injection molding conduit can be defined, for example, by at least two mold portions (not shown in the figure) when the mold portions are in the closed state. WhileFIG. 1shows a cylindrical shaped injection molding conduit having a predetermined diameter, it will be appreciated that other geometrical configurations and/or cross-sections suitable for conveying injection molding material is within the scope of the present invention. Indeed, according to alternative example embodiments, e.g., square, triangular, or any other suitably appropriate geometric shapes of the injection molding conduit are possible.

Gate portion30is positioned between runner portion40and mold cavity20and forms a transition area between the runner portion40and mold cavity20. In some embodiments, gate portion30can be formed from the cooling and/or hardening of a molten injection molding material within the injection mold conduit having corresponding structure. Gate portion30used in the present invention as illustrated inFIG. 1, is shown in more detail as gate100inFIGS. 2-6.

As seen inFIG. 2, gate100includes a sub-runner portion108, a first tab110, a second tab112, and a wing portion106. Sub-runner portion108conveys injection molding material from runner portion40to the mold cavity20of the injection mold10. Sub-runner portion108is substantially cylindrical and extends in a longitudinal direction of gate100from a first end surface114in communication with runner portion40to a second end surface116in communication with wing portion106. Sub-runner portion108is positioned between an inner surface118of first tab110and an inner surface120of second tab112, and extends past a first end surface122of first tab110.

First tab110and second tab112protrude from two opposite surfaces of sub-runner portion108and wing portion106, and extend therefrom in a first direction (first interior transverse dimension) that is substantially perpendicular to the longitudinal direction of gate100. First tab110includes a top surface126, a bottom surface128opposite to the top surface126, an outer surface130, inner surface118opposite to the outer surface130, first end surface122, and a second end surface132opposite to first end surface122. Second tab112includes in view ofFIG. 2a top surface134and inner surface120.

Wing portion106includes a top surface142, a bottom surface144opposite to the top surface142, a first side surface146, a second side surface148opposite to first side surface146, first end surface150, and a second end surface152opposite to first end surface150.

As seen inFIG. 2, first tab110is curved along a length of first tab110from first end surface122to second end surface132so as to define a structure of varying thickness and width. First tab110is curved in the first direction such that it has a greater width near a center portion and a smaller width near end surfaces122and132. Like first tab110, second tab112is also curved along a length of second tab112so as to define a structure of varying thickness and width. Like first tab110, second tab112is also curved in the first direction such that it has a greater width near a center portion and a smaller width near end surfaces.

Wing portion106extends in the longitudinal direction from the first end surface150in communication with sub-runner portion108to the second end surface152in communication with mold cavity20of the injection mold10. In addition, wing portion106extends in a second direction (second interior transverse dimension) that is perpendicular to both the first direction and the longitudinal direction from bottom surface144to top surface142. Bottom surface144and top surface142taper toward each other from the second end surface152to the first end surface150.

The dimensions of the injection molding conduit can converge moving through the conduit such that at, or near, the second end116, the second interior transverse dimension can be 2.0-10.1 times larger than the first interior transverse dimension. In an alternative embodiment, the second interior transverse dimension can be greater than 10.1 times larger than the first interior transverse dimension. The second interior transverse dimension of the injection molding conduit can be substantially aligned with a thickness of a portion of mold cavity20that is adjacent to the outlet of the injection molding conduit and/or the second interior transverse dimension can be substantially aligned with a direction in which the mold portions move relative to one another between the open state and the closed state.

In some embodiments, the second end116defining an outlet in fluid communication with mold cavity20can be larger than the thickness of a lens such that the second interior transverse dimension can be larger than a thickness of a portion of mold cavity20that is adjacent to the outlet of the injection molding conduit. When the second end outlet is larger, cooling time of an injection molding material may be increased. In some instances, the second interior transverse dimension can be between approximately 110% and approximately 200% of a portion of a thickness of mold cavity20that is adjacent to the outlet of the injection molding conduit.

In some embodiments, the first interior transverse dimension of the conduit decreases along the injection molding conduit in a direction from the first end114and toward the second end116and the second interior transverse dimension increases along the injection molding conduit in a direction from the first end114and toward the second end116.

In some embodiments, the first interior transverse dimension at, or near, the second end152of gate portion30of the injection molding conduit is approximately 1.0 mm to 3.0 mm, preferably, approximately 1.5 mm to 2.2 mm. This first interior transverse dimension can be adjusted in relation to the second interior transverse dimension to allow for optimum lens edge filling volumes and faster cooling times. The perpendicular orientation of gate portion30in relation to the lens thickness can permit increase rigidity parallel to the ejection axis of the injection mold. Additionally, a thin first interior transverse dimension permits gate portion30to be bent in one direction (e.g., about an axis running parallel with the second interior transverse dimension) and snapping off cleanly from the lens, when necessary.

In some embodiments, the length of the sub-runner portion108of the injection mold conduit can be 25% to 75% the second interior transverse dimension at the second end outlet. Preferably, the length from the sub-runner portion108is approximately 50% the second interior transverse dimension to prevent heat loss and defects in the lens. The sub-runner portion can be equal to or greater than the lens thickness (e.g., up to 30% greater). As molten material is conveyed from the sub-runner portion108to the gate portion30, a choke area can be formed allowing a more uniform filling of mold cavity20. In some embodiments, the sub-runner portion108can be further be coupled to a runner system. The runner system can include the injection mold conduit and can convey molten molding material into the sub-runner portion108. The injection mold conduit can have the same or substantially the same first and second traverse dimensions as the sub-runner portion108, and can be in fluid communication, and be reversibly coupled.

FIG. 3shows a first side view of first tab110. Bottom surface128of first tab110is angularly inclined from the first end surface122, which is positioned below a midpoint of runner portion108and wing portion106, to the second end surface132, which is situated at the midpoint of runner portion108and wing portion106. As a result, a thickness of first tab110is largest at the first end surface122and smallest at the second end surface132.

FIG. 4shows a second side view of second tab112. Second tab112includes a top surface134, a bottom surface136opposite to the top surface134, an outer surface138, a first end surface124, and a second end surface140opposite to first end surface124. Top surface134of second tab112is angularly inclined from the first end surface124, which is positioned above a midpoint of runner portion108and wing portion106to the second end surface140, which is situated at the midpoint of runner portion108and wing portion106. As a result, a thickness of first tab110is largest at the first end surface124and smallest at the second end surface140.

As shown inFIGS. 2-4, first end surfaces122and124have a curved surface profile which can be concave, while second end surfaces132and140have a straight surface profile.

FIG. 5illustrates a top view of gate100. First side surface146and second side surface148of wing portion106taper toward each other from the second end surface152to the first end surface150.

FIG. 6shows a rear view of gate100. First tab110is positioned above the midpoint of wing portion106near second end surface152of wing portion106, and second tab110is positioned below the midpoint of wing portion106near second end surface152of wing portion106. Bottom surface128of first tab110is angularly inclined downward from the first end surface122of first tab110to below the midpoint and then terminates at the second end surface132of first tab110. Top surface134of second tab112is angularly inclined upward from the first end surface124of second tab112to above the midpoint and then terminates at the second end surface140of first tab112.

In some embodiments, the injection mold conduit includes angled side cavities that permit increased turbulence and mixing of the molten molding material prior and/or during injection into the mold cavity20. During the injection molding, a portion of the molten material flow in the injection mold conduit can be diverted through the periphery of the cavities and back into the conduit at opposing angles from both sides and at a slight angle creating a vortex action. In one aspect, the injection mold conduit includes first and second cavities extending from opposing sides of, and in fluid communication with, the injection molding conduit. Each of the cavities can be defined in part by a surface that extends between the injection molding conduit and a periphery of the cavity.

In some embodiments, the surface can be angularly disposed at a non-perpendicular angle relative to a plane that can be aligned with the longitudinal axis of the injection molding conduit and can bisect the injection molding conduit and/or a line that extends along the surface in a direction from the first end of the injection molding conduit and toward the second end of the injection molding conduit can be angularly disposed at a non-perpendicular angle relative to the longitudinal axis. In some instances, the surface can be angularly disposed and/or the line that extends along the surface can be angularly disposed from approximately 1 degrees to approximately 89 degrees. Preferably, the surface can be angularly disposed and/or the line that extends along the surface can be angularly disposed from approximately 2 degrees to approximately 10 degrees. More preferably, the surface can be angularly disposed and/or the line that extends along the surface can be angularly disposed approximately 4 degrees from the horizontal axis. In addition, each of the wing portions can be angularly disposed approximately 29 degrees from the horizontal axis. The first and second cavities can terminate before the lens edge to create a small snap-gate portion for freeze off and adequate room for bending to de-gate. The gate also can also permit runner/sub-runner systems to be designed to reduce scrap molding material such that each of the cavities is spaced from the outlet of the injection molding conduit in a direction aligned with the longitudinal axis of the injection molding conduit and by a distance that can be 0.1 to 2.9 millimeters (mm), preferably, approximately 0.5 mm to 2.9 mm. The jets can terminate before the lens edge to create a small snap-gate portion for freeze off and adequate room for bending to de-gate.

In some embodiments, the injection molded article can include a product, a runner portion, and a gate portion. The gate portion can include a first end coupled to the runner portion and a second end coupled to the product (e.g., ophthalmic lens) where the gate portion is wider than the thickness of the product.

In some embodiments, the gate portion can include a first tab and a second tab that are formed by the cavities that permit increased turbulence and mixing of the molten molding material prior and/or during to injection into the mold. In some aspects, an injected molded article containing the gate portion can include the first tab and the second tab extending from opposing sides of the gate portion wherein each of the tabs is defined in part by a surface that extends between the gate and a periphery of the tab. Each of the tabs can include a surface that is angularly disposed at a non-perpendicular angle relative to a plane that is aligned with the longitudinal axis of the gate and bisects the gate and/or a line that extends along the surface in a direction from the first end of the gate and toward the second end of the gate is angularly disposed at a non-perpendicular angle relative to the longitudinal axis.

Typical injection molding materials include small beads or pellets of meltable plastics and/or resins that can be forcefully injected under heat and pressure into a mold cavity. An injection molding material can include a thermoplastic material, such as polyethyleneimine, polyetherimide, or a derivative thereof, polyethylene terephthalate, polycarbonate, polybutylene terephthalate, poly(1,4-cyclohexylidene cyclohexane-1,4-dicarboxylate), glycol-modified polycyclohexyl terephthalate, poly(phenylene oxide), polypropylene, polyethylene, polyvinyl chloride, polystyrene, polymethyl methacrylate, thermoplastic elastomer, terephthalic acid elastomer, poly(cyclohexanedimethylene terephthalate), polyethylene naphthalate, polyamide (e.g., PA6, PA66, and/or the like), polysulfone sulfonate, polyether ether ketone, polyether ketone, acrylonitrile butyldiene styrene, polyphenylene sulfide, polycarbonate/polybutylene succinate, a co-polymer thereof, or a combination thereof. A thermoplastic injection molding material can comprise a blend of high, medium, and low molecular polymers, yielding a multi-modal or bi-modal blend. Such a multi-modal material can have superior flow properties as well as satisfactory enema/physical properties. Preferably, the thermoplastic material is chosen for molding ophthalmic lenses, for example, polycarbonate.

An injection molding material can comprise a blend of polymeric and non-polymeric materials. For example, a thermoplastic injection molding material can comprise a blend of a polymer and one or more small molecule additives. Such a small molecule could be, for example, a siloxane or other lubricating molecule that, when added to the thermoplastic material, improves the flowability of the polymeric material. Other additives may include inorganic fillers such as calcium carbonate, calcium sulfate, talcs, clays (e.g., nanoclays), aluminum hydroxide, CaSiO3, glass formed into fibers or microspheres, crystalline silicas (e.g., quartz, novacite, crystallobite), magnesium hydroxide, mica, sodium sulfate, lithopone, magnesium carbonate, iron oxide, and/or organic fillers such as rice husks, straw, hemp fiber, wood flour, or wood, bamboo, or sugarcane fiber. An injection molding material can be filled (e.g., with fibers) or unfilled.