DE2518905C2 - Apparatus for manufacturing a lens from a polymerizable material - Google Patents

Description

The invention relates to an apparatus for making a lens from a polymerizable Material consisting of an upper and a lower mold half which are designed for mutual grip are around a mold cavity and a memory connected to it along its circumference / u form the excess material when the two mold halves are moved towards one another; ius the mold cavity except, with the mold cavity through one concave surface of the lower mold and one associated surface of the upper mold half is formed.

Hei a known device of this type (US PS 28 90 486) are the two mold halves after introduction of polymerizable material towards each other, with excess material from the from the mold surfaces bounded mold cavity is printed radially outward in a memory. This Memory is formed by the radius of curvature the area adjoining the mold surface of the lower mold half is enlarged, whereby between the mold surface and the upper mold half and this ίο surface with an enlarged radius of curvature a gap is formed, which gradually decreases radially from the inside out.

In the case of those produced by means of the known device Lenses, there is practically no transition between the actual lens body and that on it Lens body adjoining material area, which is made by polymerizing the material located in the memory originated. The lens produced in this way must therefore be processed in a relatively complex process be freed from the excess material.

It is also already a device zurr. Produce a lens made of a polymerizable material known (GB-PS 8 47 797). at which the diameter of the The mold surface of the lower mold half is larger than the diameter of the mold surface of the upper mold half, so that when the two mold halves move towards one another, excess "material" emerges laterally and becomes can be deposited on the protruding edge of the mold surface of the lower mold half and to compensate for material contractions occurring in the lens area is available.

However, there is no such thing in this device either

pronounced transition between the actual lens body and the adjoining this lens body

j5 ßenden material area. by polymerizing the Material has arisen from the memory.

It is an object of the invention to provide an apparatus for producing a lens from a polymerizable To create material that creates a distinct transition / wipe the actual lens body and the one adjoining this lens body by polymerizing created area.

In order to achieve this object, a device of the type mentioned at the outset is according to the invention in such a way designed that when the two mold halves engage the mold cavity and the memory over at least a constriction running in the circumferential direction of the mold cavity are connected to one another.

The device according to the invention thus has between the actual mold cavity and the memory a constriction. whereby the hardening material in this area has a much smaller material thickness than in the area of the mold cavity and in the area of the memory. The polymerized Material in this transition area have such a small material strength that it is just like a burr works. Lenses produced by means of the device according to the invention can therefore easily be removed from the excess Material to be freed. This is particularly useful when the lenses produced, in particular Contact lenses do not require any post-processing in the area of their optical surfaces, as this also applies to the Any excess material present in the margins can be removed in a simple manner.

Further refinements of the invention for alignment of the two mold halves and to maintain the constriction between the mold cavity and memory spray yourself out of the

The invention is explained in more detail below with reference to the figures showing the exemplary embodiments.

F i g. Figure 1 shows the separate mold halves of a mold for making a lens;

F i g. 2 shows the two in FIG. 1 mold halves shown in the assembled position, partially in section;

F i g. Figure 3 shows another embodiment of a mold in section;

F i g. Figure 4 shows a top view of the die of the mold from Fig. 3;

5 shows a modified male mold in combination with the die from FIGS. 1 and 2;

6 shows a plan view of a modified one Die, which, for example, together with the male die from FIGS. 1 and 2 can be used;

F i g. Figure 7 shows a section through another embodiment of a mold.

The form shown in FIGS. 1 and 2 for production A lens has a male mold 13 and a female mold 15. The patrix has a convex surface ! 7 with optical equipment that is symmetrical to the Central axis 19 lies, as well as a pair of surfaces 121 and 23 on. The surface 21 lies in a plane perpendicular to the axis 19. The surface 23 has the shape of a Section of a cylindrical surface extending concentrically to the axis 19. Seen in cross-section, the Surface 21 over a short curved surface 25 in the surface 17 over. The male part 13 has a a second pair of surfaces 27 and 29 which are aligned with the mold surface 17 and with the axis 19, d. H. the surface 27 either has the shape of a cylinder section which runs symmetrically to the axis 19, or a segment of a sphere which runs symmetrically to the axis 19. If they have the shape of a section of a cone has, the angle of inclination to the axis 19, seen in cross section, is very small. The surface 29 runs most expediently in a plane perpendicular to the axis 19. The surfaces 23 and 27 are about a further surface 31 connected to one another. This surface 3rd, is considered to be in a plane perpendicular to the axis shown running. However, it can also have a great many other contours, for example a corner section be. Finally, the male part 13 also has a cavity designated by 33. which stand out from the surface 35 extends and from a concave surface 37 and a · cylindrical surface 39. the btide at least in run approximately symmetrically to the axis 19 is limited.

The die 15 has a concave, optical equipment provided surface 41. This surface 41 ends at the edge 43. runs symmetrically to the central axis 45 and is on surfaces 49, 51, 53 and 55 with the Top surface 47 connected. The surfaces 47 and 49 run in planes perpendicular to the axis 45. Both have the shape of an unbroken ring. The surface 51 is the portion of a tapered cylinder or cone, the smallest diameter of which is at the junction with the surface 49. the Surface 55 is shown as a portion of a cylinder, but it may have any other suitable shape. the Surface 53. which is curved in cross-section! appears, connects the surfaces 51 and 55 to one another. The die 15 also has a cylindrical extension 57 on. This fortsat / 57 has a bottom surface 59 that preferably runs in a plane perpendicular to the axis 45 and the gCiTäß F i g. 1 and 2 a little below the Outer surface 61 lies so that sic a suitable base gives away.

In operation, lens material 71 is applied to the surface 41 applied. Then the male part 13 is moved relative to the female part 15 so that the surface 23 within the surface 51 is recorded and the surface 17 is at such a distance from the surface 41.

that the mold interior designated by 73 in FIG. 2 is formed. The fact that the surface 51 the Has the shape of a cone section, facilitates the joining of the two mold halves. However, the smaller diameter of surface 51 carefully so

ίο chosen with reference to the diameter of the surface 23, that the axes 19 and 45 practically coincide when the surfaces 21 and 23 completely into the Die are countersunk so that prism formation between the surfaces 17 and 41 and consequently between the surfaces of the finished lens is largely avoided.

When the male part 13 and female part 15 are joined together are, the surface 17 comes into contact with the lens material 71 and presses this outward, so that the mold cavity 73 is filled. That part of the lens material 71 which is in excess over the volume of the mold cavity 73 is present, enters the contiguous ring memory 75. of the Surfaces 51 and 53 and parts of surfaces 23 and 55 is formed. Although filling the mold cavity 73 and of the ring memory 75 do not take place at the same time, they result from the one Method step of lowering the male part 13 into the female part 15.

As in Fig. 2, the surface 21 is not in direct contact with the surface 49. but is separated from it by a thin layer of lens material 71. The diameter of the Surface 23 of the limited cylinder and the lower

The diameter of the surface 51 is dimensioned in such a way that these surfaces are practically parallel to the axes 19 and 45 run: but they are also separated from one another by a thin layer of lens material 71, whereby the lens material filling the gap between the surfaces 23 and 51 has a hydrostatic alignment of the Ach- jn 19 and 45 to one another. As a consequence of this the memory 75 sees in connection with the fluid environment, which the mold 11 and the mold cavity 73 over a constriction 77 running over the entire circumference. In addition, the memory 75 and the circumferential constriction 77 of the sealing of the mold cavity 73 against the fluid Environment in which the compound form 1 '. is located.

5 (i If the dimensions of the mold 11 are such that they are used in the manufacture of contact lenses (corneal or sklcral) from, for example, cross-linked hydrides PolyrrT'm suitable, there will be a distance between the surface 23 and the lower diameter of the surface 51 of 0.00051 cm Ms 0.0013 cm. The distance or gap between surfaces 21 and 49 is in the same area.

The dimensions given in the above example are for illustrative purposes only. It was found

floor. that the constriction must still be wide enough that Linscnmaicrial from memory 75 through the narrowing in the mold cavity 73 can be drawn in. by shrinking the initial volume of the lens material in the mold interior 53 during polymer formation

• vi created cavity.: U fill. The distance between the surfaces 21 and 49 and thus the size of the constriction 77 therefore depends on the size and shape of the cast Lens, the weight of the male mold 13. the viscosity

of the lens material used and the desired rate of polymerization. | c increases the rate of polymerization is. the greater the distance between the surfaces 21 and 49 and the wider is the constriction 77. Also the fact that the Polymer during polymer formation, as it tends to pull the mold halves together, must be taken into account will.

A clamping pressure is not only not required, but would seal the memory 75 against the mold interior 73, which is the purpose of such a memory would be wrong.

The illustrated design of the interacting surface pairs 21, 23 and 49, 51 is the preferred way of bringing the shape surface 17 into a suitable orientation relative to the shape surface 41 and delimiting the constriction 77. For the same purpose, of course, /.üiiiiVimCMw'irKcnuC ^ / uCriiüCticn an jCüCr ι GriniiiiniC can be designed in a different way, as long as the required distance, the required alignment and the required size of the constriction are achieved. For example, each of the surface pairs 21, 23 and 49, 51 can be replaced by a surface in the shape of a spherical segment. Also a surface that has a curved shape in cross section. is possible. Regardless of the design of these surfaces, the width of the constriction 77 in the example shown must be taken into account in the design of the parts 13 and 15 so that the desired distance between the mold surfaces 17 and 41 and thus the thickness of the lens is achieved. If the mold parts are provided with non-symmetrical aspherical surfaces, they must be keyed together so that the mold surfaces are properly oriented with respect to one another.

The in F ί ". 2 ^a e2C! ^TT ! C ^ .nordnun ⁰ at ^f ^ r Ίϊί * xVnjt *» of the constriction 77 results from the weight of the male part 13 and the viscosity of the lens material used, etc., is not the only one Way of holding the mold halves in the desired position and achieving the desired constriction Another arrangement is shown in Figures 3 and 4. In this second embodiment, the mold 111 consists of a male part 13 and a female part 115 Die 115 has a cylindrical extension 117, a bottom surface 119 and an outer mold surface 121, which are designed practically in the same way as the extension 57 and the surfaces 59 and 51 of the die 15. The die 115 also has a surface 123 with optical equipment , which is symmetrical to the axis 125. and a cover surface 127, which together with the mold surface 123 forms an edge 129. The surface 127 is provided with a plurality of upwardly pointing projections 131 on the edge 129. The shown first embodiment has only three such projections 131; however, other protrusions can be provided. The projections also do not have to lie directly on the edge 129, but can be arranged further outward.

In operation, as in the case of the previously described Execution of a certain amount of Linsenmaierial applied to the form surface 123. Then the The male part 13 moves relative to the female part 115 until the mold surface 17 rests on the projections 131 and. as in Fig. 3, the mold cavity! 33 forms. According to F i g. 3 axes 19 and 125 coincide. If, however, the form surface 17 is formed spherically and it rests on all projections 131. the axis 19 does not have to be in alignment with the axis 125, clamii the mold cavity 133 is symmetrical about the axis 125.

As in the previously described implementation, · ■> the surface 17 in contact with the lens material and pushes it outwards, so that the mold cavity 133 is filled when the male part 13 is sunk into the female part 115. That part of the lens material which is present in excess of the volume of the mold interior 133. gets into an annular Storage 135, which is connected to the mold cavity 133 via an annular constriction 137. The memory 135 is made up of surface 127 of die 155 and surfaces 21 and 25 and part of the Surface 17 of the patrix 13 is limited. Because of the surface tension the lens material in the memory 135 is approximately in the manner shown in FIG. 3 held position shown.

In the case of the FIGS. 3 and 4 depends on the shape shown the! level of the preliminary rating! 3! above the surface! 27

in and thus the width of the narrowing 137 of the same Factors which dictate the width of the constriction 77, d. H. the narrowing 137 must be sufficiently wide be that lens material in the store 135 is drawn through this constriction and into the mold cavity 133

2> the can to get into it by shrinking the initial volume of the monomer created during polymer formation.

If i -contact lenses, for example, made of crosslinked hydrophilic Polymers are produced, the business

) o Weight of the male part is sufficient to cover the surface of the mold 17 engaged mild protrusions: 131 to hold.

After the mold cavity and memory are filled, the lens material is polymerized in the mold cavity, during polymerization of the lens material

υ is prevented in memory. Under the term "polymerize" a polymer formation reaction is to be understood here, i.e. the polymer by: 1. the Polymerization of suitable monomers. Oligomer and / or prepolymer or 2. a crosslinking formed will.

The details of the polymerization in the mold cavity. the prevention of polymerization in the memory and the material from which the mold is made depend on the lens material chosen and the nature of the initiation of the polymer formation reaction. It can Heat or other forms of radiation such as UV light can be used. The fluid environment that the Lens material in the reservoir is exposed to it must be such that it inhibits the polymerization without eir

thus contaminating such lens material. In addition, it may be necessary to zui the memory against αιο Polymerization of the lens material in the mold cavity to shield applied radiation. Finally courage the material from which the mold halves are made be such that it is inert to the selected lens material and the desired type of polymer educational reaction allows.

As mentioned, the in FIGS. 1 and 2 as well as I. and FIGS. 4 and 4 can be used

bO to manufacture contact lenses from hydrophilic material len. With such materials, oxygen acts as an inhibitor without contaminating the material; H. if the that part of the lens material that is in the spoke that is exposed to air becomes its polymer

& 5 inhibits sation, and it remains in a liquid state.

The polymerization of the lens material should take place from the center of the mold outwards in order to avoid it that that part of the lens material in the form, de

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adjoins the edge of the mold cavity, polymerizes and thus the memory against the Mittelabschniti Blocked mold cavity. F.in way of this problem too solve, consists in polymerizing the lens material, for example with UV radiation, while one Membrane used; as shown schematically at 141 in FIG. In the case of a symmetrical lens D'-membrane 141 can be a cloudy shielding with a circular opening 143. The diameter the opening 143 should be smaller than the diameter of the lens to be cast, so that the lip material is protected against radiation at the edge of the mold. After the lens material in the center of the mold cavity is polymerized, the membrane 141 is removed so that the lens material also at the edge of the Can polymerize form. It is also possible to use a membrane with an adjustable opening. If a membrane is used, in the embodiment shown in Fig. 3, the SirahlunKsichtung preferably approximately parallel to axis 125. In this case, the mold halves are preferably made of glass or a suitable plastic that are inert to the polymerizable material and Let UV radiation through.

In the above examples, the polymerization of the Material on the lens surface in the memory is inhibited because this material is exposed to air. Preferably however, in order to facilitate subsequent handling, after the polymerization of the lens material inside of the mold cavity, the uncured material remaining in the memory is also polymerized. this can be done by placing the mold in an atmosphere of nitrogen or some other inert gas brings and irradiates the material in the store with UV radiation.

The method is not only applicable when lens material is only from the memory into the mold cavity flows. When using allyl diglycol carbonate, this material is subject to heating during the Polymerization or hardening of a temporary expansion. The memory is used to collect the initially pressed material. The molds 11 and 111 can also be used for the production of lenses a lens material can be used which is subject to permanent expansion during curing. In In this case, the mold halves 13 and 15 must be held together by sufficient force to prevent them from separating, but the force must not be so great that the mold cavity is sealed against the memory. The projections 131 on the die 115 ensure that by the force that is required to prevent the mold parts 13 and 115 from separating, the memory 135 does not seal against the mold interior 133.

After completion of the polymer formation reaction, the male mold 13 and female mold 15 and 115 become one another separated, being a finished lens of the desired thickness with a convex and a concave surface the desired contour remains. The edge created by the post-polymerization of the lens material in the Memory and the constriction is formed can be conveniently removed. As such a device for this is provided to perform an edge processing of a lens while this is on the die a If the shape adheres, the edge should also preferably adhere to the die instead of the patrix 13. This can for example can also be ensured by the fact that, for example, the surface 127 of the die 115 rings or roughs.

F. A modified form / for the production of a lens is shown in FIG. 5 shown. This mold 21 \ has a female mold 15 and a male mold 213. The patrix 213 has

^r > a longitudinal axis 215. Surfaces 219 and 221 and a cavity 223. which correspond to the longitudinal axis 19, clon surfaces 27 and 29 and the cavity 33 of the male mold 13. The Patri / .c 213 also has surfaces 225 and 227. which correspond to surfaces 23 and 31. However is

in the patrix 213 formed differently than the patrix 13, as the mold surface 231 has a recess 233, which together with the inclined surface 235 forms an edge 237. When the male part 213 is sunk into the female part 15. the surface 225 is

r> taken within the surface 51, the Axes 215 and 45 are aligned and the mold cavity 239 and the memory 241 are formed. When the mold cavity 239 is filled and also contained in the memory 241 l.inscnmaicrial is located

2 » the edge 237 opposite the edge 43 and is separated from this by a thin layer of lens material, which is exaggerated for illustration. separated. In operation, the mold 211 performs the same function as the molds 11 and 111, that is to say the edges 43 and 237 delimit an annular constriction 243.

Fig. 6 shows a modified die 315, which together can be used with a patrix 13 or 213. The die 315 has a molding surface 317. which is symmetrical to the longitudinal axis 319. The die

ίο 315 also has a surface 321 that of the surface 29 of the die 15 corresponds. The surface 321 extends outwardly from the edge 323 to a Number of surface segments 325 which are connected to one another by protruding elements 327.

Each protruding element 327 has an interior facing surface 329 and side surfaces 331 that all extend upward from surface 321 to top surface 333. The surfaces 329 lie on one imaginary cylinder surface. as by the dashed Line 335 indicated, i.e. symmetrical to the axis 319 in such a way that when the die 315 is joined together For example, a male part 13, the axes 319 and 19 are aligned with one another.

In operation, the die 315 has the same function like the female part 15. However, if, for example, the male part 13 is countersunk, a number of reservoirs are formed, which do not form a coherent, but rather a segmented ring that defines the Surrounds mold cavity and is open to this.

Each of these reservoirs is defined by a surface segment 325, opposite side faces 33., parts of the surface 321 and parts of the surface 23 of the male mold 13 are limited. A coherent annular constriction connects the individual storage elements with the mold cavity.

F i g. 7 shows a mold 411 from a male part 413 and 413 a die 15. The male part 413 is similar to the male part 13 in that it has surfaces 415 and 417 which correspond to surfaces 21 and 23 and have the function of moving axis 419 to axis 45 of die 15 to align in alignment, as in connection with the shape according to FIG. 1 and 2 described. The patrix 413 differs from the male part 13 in that it has a concave shaped surface 421 which is

b5 is moderately symmetrical to axis 419. The cavity 423 is also designed differently.

In operation, the form 411 has the same function as the shape 11. The opposing surfaces

Chen 49 and 415 together delimit a constriction 425, which defines the mold cavity 427 with the memory connects.

In addition 5 sheets of drawings

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20th

Claims (5)

Palent claims: 1. Apparatus for producing a lens from a polymerizable material, consisting of a upper and lower mold halves which are adapted for mutual engagement around a To form a mold cavity and a reservoir connected to it along its circumference, the excess material from the mold cavity when the two mold halves are moved towards one another receives, the mold cavity through a concave surface of the lower mold half and a associated surface of the upper mold half is formed, characterized in that at Engagement of the two mold halves (z. B. 13, 15) the mold cavity (73) and the memory (75) via at least a constriction (77) running in the circumferential direction of the mold cavity (73) with one another stay in contact. 2. Device according to claim ί, characterized in that that the upper and lower mold halves (13,15; 13,115) between the memory (75; 135) and Alignment devices (21, 23, 49, 51; 17.31) provided in the mold cavity (73; 133) for alignment the mold halves (13, 15; 13; (15) to the shape of the Have lens to be manufactured. 3. Device according to claim 2, characterized in that that the alignment devices have a first axial spacer (21) on the upper mold half (13) and a second axial spacer (49) on the unicrcn Mold half (15) and a first radial alignment part (23) on the upper mold half (13) and one second Radialausriditieü i51) on the lower Have mold half (15) and o'aß the Axialdislanztcile (21, 49) and the Radialausrichttcile (23, 51) when the closed form is filled with material, the constriction (77) are separated from each other. 4. Apparatus according to claim 2, characterized in that that the alignment devices (17, 131) on the lower mold half (115) outside of the latter Molding surface (123) have upwardly directed projections (131), which when the mold is closed are in engagement with the mold surface (17) of the upper mold half (13). 5. Apparatus according to claim 2, characterized in that the memory (75) is a continuous Annular space (75; 135; 241; 429) is. b. Device according to claim 2, characterized in that that the memory consists of separate ring sections.