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Jig for cnc machineRelated Patent Categories: Abrading, Abrading Process, Glass Or Stone Abrading, LensJig for cnc machine description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070173182, Jig for cnc machine. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This invention relates to jigs for Computer Numerical Control (CNC) machines and in particular to jigs for CNC machines for machining, manipulating, drilling holes in, and/or cutting the outline of, lenses for rimless spectacles. [0002] There is a requirement for being able to drill holes in spectacle lenses to receive side arms and nose rests that sit adjacent to the bridge of the wearer's nose. The perimeter shape and sizes of lenses are many and varied as are the location of the holes that are required. Furthermore, different prescriptions of optical properties dictate varying thicknesses of lenses and different contours of the concave surface of the lenses that face the eye of the wearer. [0003] The convex surface of the lens is generally of uniform curvature from one lens to another because the optical properties of the lens is achieved by machining and polishing the concave surface. The widely accepted way used throughout the ophthalmic industry for manufacturing lenses, is to take a standard circular part-spherical blank of the appropriate optical grade glass or plastic material, and bond a temporary mounting block onto the convex surface of the lens. The mounting block includes features that enable the blank to be held firmly in a jig at a predetermined datum position. This mounting block is subsequently removed only after machining and polishing work has been completed. [0004] With the lens firmly mounted by way of the mounting block in a jig, the peripheral shape or contour of the lens and the manufacture of the optical properties of the lens (by grinding and polishing the concave surface of the lens) is completed. This is usually done in two different CNC machines; one for cutting the profile and one for grinding the optical properties. [0005] The applicant has a well known machine called an "optidrill" (a Trademark of Berkshire Ophthalmic Laboratories Limited) that is used to drill holes in the finished lenses, but because the lenses arrive at the drilling machine with the mounting blocks firmly bonded to the convex surface, all drilling of the holes has to be done from the concave side of the lens. Hence the prior known optidrill comprises a vertically mounted rotary drill and a rocking table that has restricted tilting movement. The table is mounted on a two axis coordinate movement bed of a CNC machine that is controlled by software to move each lens into the correct position under the drill whilst holding the table by hand in one of two tilted positions. The tilted positions are at each end of a fairly restricted arc of movement. The drill bit enters the concave surface of the lens in a direction substantially normal to the concave surface. [0006] The applicant is also aware of a prior known drilling machine for drilling from the concave surface of the lens towards the convex surface of the lens. In this prior known apparatus the lenses are mounted flat on a two axis coordinate movement bed of a CNC machine, the lenses are not tilted, instead the drill itself is tilted through an angle so as to drill the appropriate hole. [0007] Whilst these approaches are adequate for some combinations of lens sizes and some prescriptions of optical properties, inaccuracies and wrongly directed holes often occur because of the thickness and profile of the concave surface at the point of entry of the drill. These inaccuracies have to be designed out by bending or modifying the side arms or nose rests of the frame of the spectacles. Often, additional slots have to be machined into the side edges of the lens in order to accommodate the side arms so that the lenses lie at a correct angle length of the side arms. All of this additional work is costly and leads to an unacceptable aesthetic appearance of the finished spectacles. [0008] In addition to drilling holes in lenses, it may be a requirement that the lenses undergo further cutting or edging to shape the outline of the lens. It is usual to finalise the cutting and shaping of the lenses before drilling holes in them. [0009] Presently, CNC machines manipulate the lenses so that they may be rotated around the axis substantially normal to the convex or concave surface of the lens. See for example GB 225022A, GB 583202A and U.S. Pat. No. 3,417,454A. If drilling and cutting operations are to be performed on the lens by the same CNC machine, a problem arises from the fact that lens slippage can occur about this axis when the cutting tool of the machine comes in contact with the lens. [0010] An object of the present invention is to provide a CNC machine that exploits the fact that the convex surface of most lenses are of a common profile irrespective of the size, the perimeter shape, or optical specification of the lens. The invention also exploits the fact that the mounting blocks for producing the lenses are securely bonded to the convex surface of the lens and provides a table that enables the holes to be drilled from the convex surface of the lens in a direction towards the concave surface. [0011] A further objective of the present invention is the ability to combine the two processes of shaping the edge of, and drilling into the lens. [0012] According to the one aspect of the present invention there is provided: [0013] A jig for mounting one or more lenses on a two axes coordinate movement bed of a CNC machine for machining the one or more lenses, said jig comprising a carriage having one or more lens holders for holding one or more lenses, each lens having a mounting block bonded to a convex surface of the lens, said carriage being rotatable about a first axis so as to be able to present one or more lenses to a tool of the machine at a position where it is desired to machine the one or more lenses said one or more lenses being constrained to restrict rotation of the one or more lenses about an axis normal to the concave and/or convex surfaces of the one or more lenses. [0014] The CNC machine may be provided with a lens cooling means. [0015] The carriage may be rotatable about a first axis through an angle of at least 300.degree. or could be rotatable through an angle of 360.degree.. [0016] Preferably the mounting block on the, or each, lens, has a spigot, the lens holder has one or more sockets into which the or each, mounting block fits in a predetermined position, and securing means are provided for holding the spigot in the socket. [0017] Preferably the securing means comprises a vacuum means for applying a vacuum to an underside of the or each spigot to hold the spigot in the socket but other types of securing means could be used. For example, a mechanical means, or magnetic means, or a grub screw type of fixing. [0018] Ideally the mounting block and the lens holder include features that ensure that the spigot does not revolve in the socket. [0019] Ideally the carriage is mounted in a carrier frame so that the carriage is rotatable about an axis that lies orthogonal to said first axis. [0020] In one embodiment of the present invention the tool is a drill bit for drilling holes through the one or more lenses. [0021] In another embodiment of the present invention the tool is a bit for edging, reshaping and/or cutting the outline of the one or more lenses. [0022] The present invention will now be described by way of example and with reference to the accompanying drawings in which: [0023] FIG. 1 shows a pair of rimless spectacles; [0024] FIG. 2 shows a side view of a lens mounted on a mounting block; Continue reading about Jig for cnc machine... Full patent description for Jig for cnc machine Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Jig for cnc machine patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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