CN1182664A

CN1182664A - Method for injection moulding plastic nearsight lens

Info

Publication number: CN1182664A
Application number: CN 97119733
Authority: CN
Inventors: 徐清
Original assignee: KAIDA GLASSES COMMERCIAL AND INDUSTRIAL Co WENZHOU CITY
Current assignee: KAIDA GLASSES COMMERCIAL AND INDUSTRIAL Co WENZHOU CITY
Priority date: 1997-10-10
Filing date: 1997-10-10
Publication date: 1998-05-27

Abstract

The method for injection moulding plastic nearsight lens is that, firstly the PMMA is injected into the die space formed by terrace die and first asing die, the thickness of center and edge of the die space are all smaller by delta value than that of the real one. When opening mould, the blank attaches itself to the terrace die, then the PMMA is injected again to the die space formed by blank-attached terrace die and the jecond casting die, with the thickness of center and edge of the die space are all equal to delta value, opening the mould again, the formed nearsight lens can be obtained by demoulding. When the first casting, the PMMA flows from the center to the edge, when the second casting, the PMMA flows along the equal-height flow path, the fused seam will not occur at any time, thus said invention can obtain the qualified product.

Description

A kind of injection molding forming method of plastic nearsight lens

The present invention relates to a kind of injection molding forming method of plastic nearsight lens.

PMMA is a kind of water white plastics, it also is a kind of new material of making lens, because this material price is cheap, solidify rapidly, therefore, the lens cost made from PMMA is lower, but, the PMMA lens only limits to hyperopic lens and plano lens at present, and not having the PMMA concave lens, this is because concave lens is the lens that a kind of center is thin, the edge is thick, when adopting known injection moulding process to make the PMMA concave lens, to occur welding seam inevitably, and cause the underproof cause of product.

The purpose of this invention is to provide the injection molding forming method that a kind of PMMA of employing plastics are made raw material and can definitely be guaranteed the plastic nearsight lens that product is qualified.

The present invention injects by radius of curvature respectively the PMMA of molten condition with the identical punch of the radius of curvature of the concave surface of concave lens and convex surface and formed die cavity after moulding the die matched moulds earlier, the height of the center and peripheral of this die cavity is all than the little δ value of actual (real) thickness of the center and peripheral of concave lens, and injection hole is located at the center of moulding die earlier, when cooling off the back die sinking, blank then is attached on the punch, and then with the PMMA of molten condition inject by the punch that has depended on blank with radius of curvature with the radius of curvature of the convex surface of concave lens identical after mould formed die cavity behind the die matched moulds, the height of the center and peripheral of this die cavity is equal to the δ value, and injection hole is located at the marginal position of die cavity, after cooling off die sinking once more, can be with the concave lens of moulding ejection device from the punch.

The essence of said method is post forming, in first time forming process, the PMMA of molten condition under high pressure flows to the edge equably from the center, seam can not appear welding, but when die sinking, can on blank, stay around mouth, in second time forming process, the PMMA of molten condition under high pressure flows to opposite side along die cavity runner contour but width gradual change from injection hole, seam also can not appear welding, and the PMMA that dissolves state also can make the fusion and the cast gate on the blank is disappeared once more of blank surface, this shows that the present invention can produce qualified PMMA concave lens, practice is proof also, the PMMA concave lens of being made by this method is qualified fully.

Further illustrate detailed content of the present invention below in conjunction with drawings and Examples.

Fig. 1: the cutaway view of concave lens;

Fig. 2: punch is moulded the cavity structure schematic diagram behind the die matched moulds together earlier;

Fig. 3: blank is with the comparison diagram of concave lens;

Fig. 4: the punch that has depended on blank with after mould cavity structure schematic diagram behind the die matched moulds;

Fig. 5: the structural representation that moves axially mould;

Fig. 6: the structural representation of horizontal mobile mould;

Fig. 7: A-A cutaway view.

As shown in the figure, the injection molding forming method of a kind of PMMA concave lens of the present invention at first is that the PMMA of molten condition is injected by radius of curvature R, r ₁Respectively with the radius of curvature R of the concave surface and the convex surface of concave lens ₀, r ₀Identical punch 1 and mould die 2 matched moulds earlier after in the formed die cavity 3, the height of the center and peripheral of this die cavity 3 is all than the little δ value of actual (real) thickness of the center and peripheral of concave lens, and injection hole 4 is located at the center of moulding die 2 earlier, when cooling off the back die sinking, 5 of blanks are attached on the punch 1, and then the PMMA of molten condition is injected by the punch 1 that has depended on blank 5 with radius of curvature r ₂Radius of curvature r with the convex surface of concave lens ₀Mould after identical behind die 6 matched moulds in the formed die cavity 7, the height of the center and peripheral of this die cavity 7 is equal to the δ value, and injection hole 8 is located at the marginal position of die cavity 7, after cooling off die sinking once more, and can be with the concave lens of moulding ejection device from the punch 1.Temperature during the PMMA molten condition is 215 ℃-240 ℃, and general clock more than a minute gets final product die sinking after the injection moulding.At the mould design aspect, usually with punch 1 as moving axially mould design, on horizontal injection press, move axially mould 1 and do axially intermittently to move back and forth; Mould earlier die 2 and after to mould die 6 be to design as horizontal mobile mould, on horizontal injection press, horizontal mobile mould is done the horizontal motion that enters and withdraw from, make on the horizontal mobile mould mould earlier die 2 and after mould die 6 and take turns coaxial mobile mould and align.Present embodiment is moving axially six punch 1 of layout on the mould, arranging on the horizontal mobile mould that six are moulded die 6 after moulding die 2 and six earlier, and mould earlier for six and mould die 6 behind die 2 and six in that six punch 1 on the coaxial mobile mould are corresponding one by one respectively on the position, be located at each injection hole 4 of moulding earlier on die 2 centers and be laid in actinomorphic runner 9 communications of being of the horizontal mobile mould back side together, the emission center of this runner 9 then aligns with the total injection hole 11 on the quiet template 10.Injection hole 8 is located on the edge of punch 1, and link up with being laid in the actinomorphic runner 12 that is that moves axially on the mould, the emission center of this runner 12 aligns with being located at the injection molding channel 13 of moulding the symmetrical centre of die 6 behind six of horizontal mobile mould and aligning with total injection hole 11.When punch 1 when moulding die 2 matched moulds earlier, from the edge of moulding die 2 earlier of the protrusion of surface of horizontal mobile mould then with injection hole 8 shutoff.Horizontal mobile mould should dispose transverse moving mechanism, and this mechanism is made up of with the guide groove 15 that is arranged on the horizontal mobile mould the guide pillar 14 that is fixed on the quiet template 10.During matched moulds, guide pillar 14 inserts and is located in the guide hole 16 that moves axially mould, and during die sinking, horizontal mobile mould has the process of an axial displacement, limits its shift length but be arranged on the guide pillar 14 and with the guide hole 16 sliding limited blocks of joining 17.Because the surface area of punch 1 is greater than the surface area of moulding die 2 earlier, simultaneously, the bore of primary injection hole 4 is very little, and therefore, during die sinking for the first time, blank 5 is attached on the punch 1 naturally.Common structure according to mould moves axially on the mould and also should be provided with cast gate drag hook 17, demoulding push rod 18 and backhaul guide pillar 19 etc.

Claims

1, a kind of injection molding forming method of plastic nearsight lens is characterized in that: at first be that the PMMA of molten condition is injected by radius of curvature (R, r ₁) respectively with the concave surface of concave lens and the radius of curvature (R of convex surface ₀, r ₀) identical punch (1) and mould die (2) matched moulds earlier after in the formed die cavity (3), the height of the center and peripheral of this die cavity (3) is all than the little δ value of actual (real) thickness of the center and peripheral of concave lens, and injection hole (4) is located at the center of moulding die (2) earlier, when cooling off the back die sinking, blank (5) then is attached on the punch (1), and then the PMMA of molten condition is injected by the same radius of curvature (r of punch (1) that has depended on blank (5) ₂) with the radius of curvature (r of the convex surface of concave lens ₀) mould after identical behind die (6) matched moulds in the formed die cavity (7), the height of the center and peripheral of this die cavity (7) is equal to the δ value, and injection hole (8) is located at the marginal position of die cavity (7), after cooling off die sinking once more, the concave lens of moulding can be gone up ejection device from punch (1).