IMPROVED MACHINE FOR DIAMOND TURNING AND POLISHING CONTACT LENSES AND THE LIKE

Abstract: Machines for turning and polishing contact lenses. A drawback experienced with known machines for this purpose is that vibration created by a prime mover, e.g. an electric motor, is transmitted to a driven rotatable support for a lens. This is detrimental to the surface finish imparted to the lens by a tool. The above drawback is eliminated by the present invention by transmitting the drive from a prime mover (2) to said lens support (7a) by a magnetic coupling (3, 6) which avoids physical contact between the lens support (7a) and said prime mover (2).

Description: IΠPRQVED MACHINE FOR DIAMOND TURNING AND POLISHING CONTACT LENSES AND THE LIKE This invention relates to an improved machine for diamond turning and polishing contact lenses and the like. Drawbacks experienced with existing known machines for this purpose are briefly that due to vibration caused by betueen relatively moving parts of the machine it is net always possible to obtain a good surface finish to the lenses and tc maintain the required accuracy and geometry thereof. Also, the production of high quality lenses at present depends to a great extent upon the skill of operatives and unless expertly and efficiently carried out breakage of or damage to both the lenses and the diamond turning or polishing tccls can easily result. The object of the invention is to provide a machine for diamond turning and polishing contact lenses or the like which eliminates the drawbacks above referred to and enables.high quality accurate lenses to be obtained and the risk of breakage both of lenses and tools avoided, or substantially so. Broadly, according to the present invention, there is provided a machine for diamond turning and polishing contact lenses or the like wherein the drive from a prime mover, e.g. an electric motor, to means for rotatably supporting a uorkpiece, is effected through the intermediar of a magnetic coupling that avoids transmission of vibration of said prime mover, or mechanism assocated therewith, to said rσtatable support means. In addition to the above, vibration is still further avoided by an arrangement of bearings as will hereinafter be made apparent. Still further, breakage is avoided by a predetermined torque between the two magnets of the magnetic coupling resulting in the means rotatably supporting the workpiecβ being stopped in the event of excessive pressure being exerted between the uorkpiece and a tool acting thereon. An advantage also resulting from this invention is that mechanical noise is significantly reduced during operation αf the machine. To enable the invention to be clearly understood and readily carried into effect a preferred embodiment thereof will now be described by way of example with reference to the accompanying purely diagrammatic drawings wherein:- O rl Figure 1 is a part sectional side elevation of the apparatus and Figure 2 is a longitudinal section taken through the casing of the apparatus. Referring firstly to Figure 1, the apparatus comprises a shaft 1 driven in both clockwise and anti-clockwise directions by a printed armature motor 2, the shaft 1 transmitting a drive to the machine -r spindle 7 by way of a magnetic coupling comprising inner and outer ceramic magnets 6 and 3 respectively supported by metal adaptors 5 and 4. The magnet 6, by way of its adaptor 5, is fixed to' he drive shaft 1 and the magnet 3, by way of its adaptor 4 is fixed to * . he spindl 7. The magnets 3 and 6 are aligned in order that the magnetic force between the two will drive the spindle 7 without physical contact between the spindle 7 and the motor 2 when the latter is activated. It will be readily appreciated that by means of the arrangement described above that no vibration is transmitted by the motor 2 to the machine spindle 7 as would normally occur with known machines due to poor quality bearings, the use of a belt drive, lack of stability and excessive machine tolerances generally. Referring next to Figure 2, the machine spindle 7 is hollow and is mounted to rotate in bearings in a casing S, said bearings comprising self-aligning angular contact ball races 9 and 10 having spacers 11 and 12 interposed therebetween, and a self-aligning angular contact ball race 13 mounted in a sleeve 14, a spacer 15 being interposed between this latter bearing and the bearing 10. This assembly of bearings, which ensures stability of rotation of the spindle 7, is held in position in the casing 8 by retaining rings 16 and 17 at the ends of the casing 8. The casing B is mounted on a metal bed (not shown) ensuring that the machine is very stable. A work piece, e.g. a contact lens, is supported within a tapered adaptor 7_ fitted to or formed integral with, the front end of the machine shaft or spindle 7. In a further embodiment of the invention which is not illustrated, the machine spindle is supported by a minimum total of two bearings. At least one ball race is provided at the end of the spindle adjacent the workpiece-rεceiving adaptor and at the end of the spindle adjacent the magnetic coupling and drive shaft. These bearings may be separated by a spacer or suitable spacing means. Suitable bearings in all embodiments include angular contact ball races which may additionally be self-aligning. The provision of the magnetic drive coupling above described also overcomes the problem of tool breakage that has previously been experienced with known machines because a predetermined braking torque between the two magnets 3 and 6 ensures that the spindle 7 will immediately stop if the diamond turning tool is plunged into the workpiece and excessive pressure created between the latter and the tool. With a conventional belt drive mechanism a diamond turning tool would be damaged because of theaitgόinginertia in the spindle 7. Preferably the electric motor 2 is a D.C. motor as this has low vibration. Although this invention is primarily concerned with the diamond turning and polishing of contact lenses, it is to be appreciated that it can be adapted to be used for analogous purposes, such as for the diamond turning and polishing of lenses or the like for scientific apparatus such as those for cameras; optical apparatus, microscopes and the working of any non-ferrous or precious metal or plastic component parts.

Claims: CLAIMSt 1* A machine for diamond turning and polishing contact lenses or the like characterised in that the drive from a prime mover, e.g. an electric motor, to means for rotatably supporting a workpiece, is effected through the intermediary of a magnetic coupling that avoids transmission of vibration of said prime mover, or mechanism associated therewith, to said rotatabie support means. 2. A machine as claimed in Claim 1, characterised in that said magnetic coupling comprises inner and outer magnets supported by adaptors fitted respectively to a driving shaft and a machine spindle provided or formed integral with an adaptor for receiving a workpiece, e.g. a contact lens, the magnetic force between the two magnets being such that the coupling will drive the machine spindle without physical contact between the spindle and the electric motor, when the latter is actuated. 3. A machine as claimed in Claim 2 characterised in that the machine spindle is mounted to rotate in bearings within a casing, said spindle at its end adjacent the workpiece-receiving adaptor being - supported by at least one bearing and the end of said spindle adjacent the driving shaft and magnetic coupling being supported by at least one bearing. 4. A machine as claimed in Claim 3 characterised in that a spacer or other spacing means is interposed between said bearings supporting the spindle. . 5. A machine as claimed in any of Claims 2 to 4 characterised in that the machine spindle is mounted to rotate in bearings within a casing, said spindle at its end and adjacent to that provided with the workpiece-receiving adaptor being supported by a paid of ball races, and the end of the spindle adjacent the driving shaft and magnetic coupling being supported by a ball race. 6. A machine as claimed in Claim 5 characterised in that a spacer -r is interposed between said pair of ball races and between said ball race and said pair of ball races. 7. A machine as claimed in any of Claims 3 to 6 characterised in that the ball races are angular contact bearings. 8. A machine according to Claims 2 or 3, characterised in that a predetermined braking torque between the two magnets is such as to ensure that the machine spindle will immediately stop if excessive pressure is created between a workpiece and the tool. 9 * A machine for diamond turning and polishing contact lenses and the like constructed and adapted to function substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.

Inventors: GIBBS P
Applicants: CHASE DIAMOND TOOLS, GIBBS P, CHASE DIAMOND TOOLS LTD
Application year: 1981
Main classification: B24B47
IPC codes: B23Q1, B23Q5, B24B13, B24B47, H02K49