Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1998-07-23
2001-05-01
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S388000, C451S390000
Reexamination Certificate
active
06224467
ABSTRACT:
The present application is based on Japanese Patent Application No. 9-206743 filed Jul. 31, 1997, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing an ocular lens such as a contact lens or an intraocular lens, and lens blank holders and a lens blank loader/unloader, which are used in producing the ocular lens. More specifically, the present invention is concerned with such a method of producing an ocular lens by effecting cutting operations on a lens blank which gives one ocular lens, so that the produced ocular lens has desired front and back curved surfaces. The invention also relates to lens blank holders for holding the lens blank, by which the lens blank is supported on a front and a back surface cutting device during the cutting operations on the lens blank for forming an intended ocular lens having the back and the front curved surfaces. The invention also relates to a lens blank loading and unloading device for loading and unloading the lens blank on and from the front or back surface cutting device.
2. Discussion of the Related Art
In a conventional method of producing an ocular lens as disclosed in JP-A-1-101319 and JP-A-7-195556, for instance, a lens blank formed of a suitable material and having a size that gives an ocular lens is bonded to a lens blank holder, which is in turn attached to a spindle of a cutting device, so that the lens blank is machined for forming the intended ocular lens having a back and a front curved surface. In this method, one of the opposite surfaces of the lens blank is first machined while the other surface is bonded to the lens blank holder. Subsequently, the lens blank is removed from the lens blank holder, and the above-indicated other surface which has been bonded to the lens blank holder is then machined while the above-indicated one surface which has been machined is bonded to the lens blank holder. Thus, the opposite surfaces of the lens blank are machined to give the desired back and front curved surfaces of the ocular lens.
In the method indicated above, however, it is required to bond the lens blank to the blank holder, remove the lens blank therefrom, and clean the lens blank to remove the bonding agent after each of the opposite surfaces of the lens blank has been subjected to the cutting operation. Accordingly, the above method is cumbersome and time-consuming, resulting in low production efficiency of the ocular lens. The cutting operations on the lens blank need to be effected by taking account of the thickness of a layer of the bonding adhesive applied between each surface of the lens blank and the blank holder. However, it is difficult to effect the cutting operations on the lens blank for forming the ocular lens with high accuracy while accurately controlling the thickness of the adhesive layer. In some cases, the thickness of the obtained ocular lens may vary due to a variation of the thickness of the layer of the adhesive applied between the lens blank surface and the lens blank holder.
When the lens blank is bonded to the blank holder, the axis of the lens blank needs to be accurately positioned relative to the axis of the spindle of the cutting device, so that the produced lens has an optical axis. However, no technique has been established for assuring accurate and easy positioning of the lens blank relative to the blank holder when the lens blank is bonded to the lens blank holder. It is accordingly difficult to accurately position the lens blank relative to the spindle of the cutting device.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of producing an ocular lens by effecting cutting operations on a lens blank. It is also an object of the present invention to provide lens blank holders and a lens blank loading and unloading device, which can be suitably used in producing the ocular lens.
More specifically described, it is a first object of the present invention to provide a method of producing an ocular lens from a lens blank, which permits easy attachment and removal of the lens blank to and from a spindle of a front or a back surface cutting device, so as to assure accuracy of positioning of the lens blank relative to the spindle for producing the ocular lens having an intended optical characteristic, with high accuracy and production efficiency.
It is a second object of the present invention to provide a lens blank holder for holding a lens blank during a back surface cutting operation of the blank, which lens blank holder permits the lens blank to be supported on a spindle of a back surface cutting device with high positioning accuracy, while permitting easy attachment and removal of the lens blank to and from the spindle, so that an intended ocular lens having a desired back curved surface is produced with ease and high precision.
It is a third object of the present invention to provide a lens blank holder for holding an intermediate lens blank during a front surface cutting operation of the lens blank whose back surface has been cut to form the back curved surface of an ocular lens, which lens blank holder permits the intermediate lens blank to be supported on a spindle of a front surface cutting device with high positioning accuracy, while permitting easy attachment and removal of the intermediate lens blank to and from the spindle, so that the intended ocular lens having a desired front curved surface is produced with ease and high precision.
It is a fourth object of the present invention to provide a lens blank loading and unloading device for loading and unloading a lens blank on and from a spindle of a surface cutting device, which device permits the lens blank to be easily supported on the spindle of the cutting device with high positioning accuracy and to be easily removed from the cutting device.
The above first object of the present invention may be attained according to a first aspect of the invention, which provides a method of producing an ocular lens, comprising the steps of: (a) preparing a lens blank which gives an ocular lens, the lens blank having a concave back surface and a convex front surface, at least a portion of the front surface being tapered to give a tapered surface; (b) forming a back curved surface of the ocular lens by effecting a cutting operation on the concave back surface of the lens blank, while the lens blank is supported on a spindle of a back surface cutting device such that the tapered surface of the lens blank is drawn onto a tapered holding surface of the spindle under a negative pressure applied to the lens blank, the tapered holding surface following a profile of the tapered surface of the lens blank; and (c) forming a front curved surface of the ocular lens by effecting a cutting operation on the front surface of the lens blank whose back surface has been cut to form the back curved surface, while the lens blank is supported on a spindle of a front surface cutting device such that the back curved surface of the lens blank is drawn onto a holding surface of the spindle of the front surface cutting device under a negative pressure applied to the lens blank.
In the method described above, the lens blank is subjected to cutting operations for forming the front and back curved surfaces of the intended ocular lens, with the lens blank being supported or held on the spindle of the front and back surface cutting devices with a suction force, i.e., under a negative pressure applied to the lens blank. According to this method, the lens blank can be easily and quickly attached to and removed from the front or back surface cutting device, so as to assure a significantly improved production efficiency of the ocular lens, as compared with the conventional method in which the lens blank is bonded with an adhesive to a suitable device adapted to hold the lens blank during the cutting operations.
In the present method, the lens blank can be positioned relative to the spindle of the back surface cutting device suc
Ichikawa Seiichi
Miura Toshikazu
Sasaki Masahiro
Tajima Hiroyuki
Tanaka Yuki
Burr & Brown
Eley Timothy V.
Menicon Co. Ltd.
Nguyen Dung Van
LandOfFree
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