Method and device for cleaning a molding surface of a reusable lens mold

Abstract

A method for cleaning a molding surface (51) of a reusable lens mold (5), in particular of a reusable lens mold (5) for molding ophthalmic lenses such as soft contact lenses, comprising the steps of: generating a jet (3) of deionized water, exposing the molding surface (51) of the reusable lens mold (5) to the jet (3) of deionized water,
wherein the jet (3) of deionized water has a circular full cone spray pattern and impinges on the molding surface (51) of the reusable lens mold (5), and wherein the circular full cone spray pattern has a uniform distribution of the volume flow of deionized water over the base of the cone of the circular full cone spray pattern.

Claims

1. Method for cleaning a molding surface of a reusable lens mold for molding soft contact lenses, the method comprising the steps of: generating a jet of deionized water, exposing the molding surface of the reusable lens mold to the jet of deionized water, wherein the jet of deionized water has a circular full cone spray pattern and impinges on the molding surface of the reusable lens mold, and wherein the circular full cone spray pattern has the shape of a cone having a circular base.

2. Method according to claim 1, wherein the reusable lens mold comprises an annular metallic mask in particular a chromium mask, which is arranged at a radially outer boundary of the molding surface.

3. Method according to claim 1, wherein the reusable lens mold is transported through the jet of deionized water along a linear transport path.

4. Method according to claim 3, wherein a plurality of jets of deionized water are linearly arranged at fixed locations, and wherein the reusable lens mold is transported through the plurality of jets along the linear transport path which extends along the linear arrangement of the plurality of jets.

5. Method according to claim 1, wherein an apex of the molding surface of the reusable lens mold and a discharge orifice from which the jet of deionized water having the full cone spray pattern is ejected are arranged to be spaced by a predetermined impact distance (d).

6. Method according to claim 5, wherein the predetermined impact distance (d) is in the range of 30 mm to 60 mm.

7. Method according to claim 5, wherein the jet has a cone angle () in the range of 80 to 100.

8. Method according to claim 5, wherein a flow rate of deionized water at a pressure of 4.10.sup.5 Pa is in the range of 0.40 l/min to 0.60 l/min.

9. Method according to claim 1, wherein the jet is generated with the aid of a full cone nozzle.

10. Method according to claim 3, wherein the reusable lens mold is transported along the linear transport path at a velocity in the range of 100 mm/s to 200 mm/s.

11. Method according to claim 4, wherein the individual jets of the plurality of linearly arranged jets are arranged in a manner such that they do not overlap at a predetermined impact distance (d).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantageous aspects of the invention become apparent from the following description of embodiments of the invention with the aid of the drawings in which:

(2) FIG. 1 is a schematic view of essential components of an embodiment of an apparatus according to the invention comprising a plurality of linearly arranged full cone nozzles, and a male mold being arranged at a predetermined impact distance relative to the discharge orifice of the full cone nozzles,

(3) FIG. 2 is a schematic representation of an embodiment of a full cone nozzle suitable for the apparatus and method according to the invention,

(4) FIG. 3 is a partial longitudinal section of the full cone nozzle shown in FIG. 2, and

(5) FIG. 4 is a longitudinal section of another embodiment of a full cone nozzle suitable for the apparatus and method according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) FIG. 1 shows essential components of an embodiment of an apparatus according to the invention for cleaning a molding surface 51 of a reusable lens mold 5, in the embodiment shown of a reusable male mold 5 for molding an ophthalmic lens such as a soft contact lens. The apparatus comprises a spray system 1 comprising a plurality of linearly arranged full cone nozzles 2, in the embodiment shown in FIG. 1 four such full cone nozzles 2 are shown by way of example. The full cone nozzles 2 are preferably of the type axial-flow full cone nozzle and are available from the company Lechler GmbH, Ulmer Str. 128, DE-72555 Metzingen, Germany, although alternatively nozzles of the type tangential-flow full cone nozzle may be used as well. The reusable male mold 5 shown in FIG. 1 comprises an annular metallic mask 52 (e.g. chromium mask) arranged at and/or forming the radially outer boundary of a molding surface 51 of the reusable male mold 5.

(7) The reusable male mold 5 shown in FIG. 1 has been used in a soft contact lens molding process and must now be cleaned and dried before it can be re-used for molding the next lens. Cleaning of the male mold 5 may comprise several cleaning steps and a final rinsing step in which the male mold 5 is exposed to deionized water after it has been cleaned in one or more preceding cleaning steps in which liquids other than deionized water are typically used which are less aggressive to the chromium mask than is deionized water. However, at least in the final rinsing step deionized water is used. After the final rinsing step, the mold is dried and is ready for being reused.

(8) For the final rinsing step, the reusable male mold 5 is transported to the spray system 1 comprising the plurality of linearly arranged full cone nozzles 2. Similarly, the corresponding reusable female mold may be cleaned/rinsed in a similar manner (although not being provided with a chromium mask). For the sake of simplicity in the following only the cleaning/rinsing of the reusable male mold 5 comprising the chromium mask 52 will be described in more detail making reference to the final rinsing step in which deionized water is used. In the embodiment shown in FIG. 1, the full cone nozzles 2 of the spray system 1 are linearly arranged at fixed locations along a common supply pipe 4 and are connected to the common supply pipe 4 to in operation generate four individual jets 3 of deionized water. Each individual jet 3 of deionized water has a circular full cone spray pattern as can be seen from FIG. 1 in which the base of the cone is also indicated schematically. As the reusable male mold 5 is transported (using a suitable transportation device, not shown) along a linear transport path (indicated by the arrow shown in FIG. 1) which extends along the linearly arranged full cone nozzles 2, the molding surface 51 bounded by the chromium mask 52 of the reusable male mold 5 is successively impacted by the jets 3 of deionized water ejected from the full cone nozzles 2. The (lateral) distance between the discharging orifices 23 of adjacently arranged full cone nozzles 2 may, for example, be in the range of 30 mm to 60 mm, and may in particular be 40 mm. Transportation of the reusable male mold 5 may be performed at a velocity in the range of 100 mm/s to 200 mm/s, for example this velocity may be 180 mm/s.

(9) The jet 3 created by the respective individual full cone nozzles 2 preferably has a cone angle which may, for example, be in the range of 80 to 100, and may in particular be 90. The impact distance d (FIG. 1), that is to say the distance between the discharge orifice 23 (see FIG. 3) of the full cone nozzle 2 and the apex of the molding surface 51 of the reusable male mold 5 may generally be in the range of 15 mm to 25 mm, more particularly in the range of 15 mm to 25 mm, and may in for example be 22.5 mm. By way of example, the flow rate of deionized water through the individual full cone nozzles 2 at a pressure of 4.Math.10.sup.5 Pa (corresponding to a pressure of 4 bars) may be in the range of 0.40 l/min (liters per minute) to 0.60 l/min. By way of example, too, the deionized water may be supplied to the respective full cone nozzles 2 at a pressure which is in the range of 1.Math.10.sup.5 Pa to 6.Math.10.sup.5 Pa (corresponding to 1 to 6 bars), particularly at a pressure of 2.5.Math.10.sup.5 Pa (2.5 bars). In particular, the amount of liquid per area and per minute may be selected to be smaller than 1 ml per minute and per square millimeter (1 ml/min.Math.mm.sup.2) at a pressure of 4 bars and at an impact distance of 15 mm.

(10) As has been mentioned already, in operation the full cone nozzles 2 are embodied to generate a uniform distribution of the volume flow of deionized water over the base of the cone of the circular full cone spray pattern, so that for example the variation of the volume flow over the entire impact area may be less than 10%. As can be seen from FIG. 1, the full cone nozzles 2 are arranged such that the circular full cone spray patterns generated by adjacently arranged full cone nozzles 2 do not overlap when the mold surface 51 of the male mold 5 is arranged at the above-described impact distance d.

(11) A first embodiment of a full cone nozzle 2 suitable for the apparatus and method according to the invention is shown in FIG. 2 and FIG. 3. This embodiment of the full cone nozzle 2 comprises an elongated hollow nozzle body 21 comprising at one end thereof a radially outwardly projecting flange 22, so that with the aid of a retainer nut 220 the nozzle 2 can be screw-mounted onto a connecting spout 41 which in turn is connected (e.g. welded) to the common supply pipe 4.

(12) FIG. 4 shows a second embodiment of a full cone nozzle 2 which may be provided with a thread on the outer surface of the nozzle body so that it can be directly screw-mounted to the connecting spout 41 which in turn is connected to the common supply pipe 4. A hex head 28 is provided on the nozzle body allowing for wrench tightening of the full cone nozzle 2 during screw-mounting the nozzle 2 to the connecting spout 41.

(13) The embodiments of the full cone nozzles shown in FIG. 2, FIG. 3, and FIG. 4 allow for an easy replacement, if necessary. In the full cone nozzles 2 shown in FIG. 2, FIG. 3 and FIG. 4, the elongated hollow nozzle body 21 has an axial liquid passageway 24 for communicating with the spout 41. At the discharge orifice 23 located at the downstream end of the nozzle body 21 the full cone nozzle 2 comprises an outwardly extending frustoconical section 25.

(14) Axial-flow full cone nozzles are of the type turbulence nozzle. In a turbulence nozzle, the deionized water rotates through a chamber 27 while proceeding to the discharge orifice 23 of the full cone liquid nozzle 2. Thus, the jet 3 ejected from the discharge orifice has the desired full cone spray pattern.

(15) In the particular case of an axial-flow full cone nozzle 2 shown in longitudinal section in FIG. 3 and FIG. 4, one or more vanes 26 are arranged in the passageway 24 between the upstream end of the nozzle body 21 and the discharge orifice 23 of the full cone liquid nozzle 2. The one or more vanes 26 arranged in the nozzle body 21 impart a swirling movement to the deionized water passing through the nozzle body 21 and breaks up the deionized water flow into liquid droplets which are uniformly distributed over the base of the full cone spray pattern of the jet 3 emitted from the discharge orifice 23 of the full cone liquid nozzle 2. The full cone liquid nozzle 2 thus creates a very uniform liquid spray pattern which is superior to the uniformity of conventional spray nozzles, for example flat jet nozzles.

(16) Other nozzle types are suitable for the generation of a circular full cone spray pattern having a uniform distribution of the volume flow of deionized water over the base of the cone as well such as, for example, tangential-flow full cone nozzles. In a tangential-flow full cone nozzle, the deionized water is typically supplied tangentially to a swirl chamber. Suitable tangential-flow full cone nozzles are available from the company Lechler GmbH, Ulmer Str. 128, DE-72555 Metzingen, Germany, as well.

(17) In operation, in the embodiment illustrated in FIG. 1 the individual jets 3 of deionized water having the full cone spray pattern are ejected from the full cone nozzles 2, with the full cone spray pattern having a cone angle which is preferably between 80 and 100, and is particularly 90. As indicated previously, the full cone liquid nozzles 2 are arranged such that the jets of adjacently arranged full cone nozzles 2 do not overlap at the impact distance d.

(18) By way of example, the full cone nozzle 2 may be made of PVDF (polyvinylidene fluoride), brass, Hastelloy, Titanium or stainless steel, or of suitable thermoplastic polymeric materials such as, for example, PVC (polyvinyl chloride), polypropylene or Teflon.

(19) Although the invention has been described with the aid of specific embodiments, it is evident to the person skilled in the art that this embodiment has been described by way of example only and that various changes and modifications are conceivable without departing from the teaching underlying the invention. Therefore, the scope of protection is not intended to be limited by the embodiments described, but rather is defined by the appended claims.