Metal working – Method of mechanical manufacture – Disassembling
Patent
1985-12-18
1987-07-07
Moon, Charlie T.
Metal working
Method of mechanical manufacture
Disassembling
294263, 29468, 29559, 51217L, 51216LP, 51284R, 51277, 156295, 156344, B23P 1900
Patent
active
046777296
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the manufacture of lenses, especially contact lenses.
Contact lenses are conventionally manufactured by machining suitably sized lens blanks on automatic or semi-automatic lathes. Although according to some machining procedures the lens blank itself is received into the collet of the lathe the more commonly adopted methods involve attaching the lens blank to a chuck which is then received in the lathe collet. After the first curved lens surface has been cut on the blank it is necessary to remove the partly machined blank from the chuck and to then attach it to the second chuck (known in the contact lens art as a "block") so that the opposite lens surface can be formed. This procedure of mounting a partly machined lens blank on a block is known in the art as "blocking". One difficulty in carrying out the blocking operation is to ensure that the optical axis of the partly machined blank is aligned with the axis of the block so that the second lens surface will be cut on the same axis as the first. This procedure is conventionally carried out by manually aligning the blocks and the lens blank and is accordingly an extremely laborious and skilled operation. Failure to achieve accurate alignment of the lens blank and block will lead to the rejection of the lens in final checking owing the poor edge control or prism.
According to the present invention there is provided a method of mounting a partly formed lens blank, having a first lens surface, on a block in order to be able to cut a second lens surface on the blank, said method comprising bringing the block into contact with the first lens surface of the partly formed, e.g. machined, blank while maintaining the axes of the block and blank in a vertical disposition and, while supporting the lower component of the block or blank so that it is free to move in any direction in a plane at right angles to the axes of the block and blank, urging the lens surface and block firmly together with a uniform film of liquid adhesive therebetween, whereby said liquid film acts as a lubricant between the mating surfaces of the block and the lens surface and assists centralisation and alignment of the axes of the blank and block.
The block is conveniently lowered onto a blank, which is supported so that its optical axis is maintained in a vertical disposition, while being free to move to a limited extent in a horizontal plane. If the partly machined lens blank has been machined to form the first lens surface while supported on a chuck, the blank may be transferred directly from its associated chuck to a block.
According to a further aspect of the invention there is provided a blocking machine for centring a partly machined lens blank having a first lens surface to a block in order to machine the opposite lens surface, said machine comprising a holder for supporting one of the components comprising the block and lens blank above a moveable table for supporting the other component, said table in at least one mode, being free to move in any direction in a horizontal plane and means for moving the holder and table towards each other and bringing the first lens surface and block into mutual contact. Preferably, the lens blank is attached to a chuck and the lens blank and chuck supported by the table, while the block is mounted in the holder and lowered under the weight of the holder and block onto the lens blank. The table on which the lens blank and chuck is supported is arranged to be freely moveable in a horizontal plane and this can be achieved by supporting the table on ball-bearings. Preferably the table includes means for selectively locking and unlocking the table so that after the transfer operation, the table can be held solidly.
While the chucks and blocks can be loaded by hand into the holder and table the blocking machine is preferably designed to be loaded and unloaded automatically. The apparatus may include means for automatically applying adhesive to the block and means for breaking the bond between the chuck and the lens after the blank h
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Morland Albert H.
Phoenix John T.
CooperVision, Inc.
Moon Charlie T.
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