Device for edge-machining of optical lenses

Details Device for edge-machining of optical lenses Device for edge-machining of optical lenses

2002-03-21

2004-03-30

Nguyen, Dung Van (Department: 3723)

Abrading

Precision device or process - or with condition responsive...

With feeding of tool or work holder

C451S057000, C451S044000

Reexamination Certificate

active

06712671

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a device for edge-machining of an optical lens. In particular, the invention relates to a CNC-controlled device, suitable for industrial use, for edge-machining of spectacle lenses, which allows spectacle lenses to be finish-machined at the edges even in relatively large numbers with the necessary precision in very short machining times.
Where the term spectacle lenses is used below, it should be understood to mean optical lenses or lens blanks for spectacles made of the usual materials, such as polycarbonate, inorganic glass, CR-39, HI-Index etc., and with circumferential edges of any shape, which lenses or lens blanks may be, but do not have to be, machined on one or both optically effective surfaces prior to machining of the edge thereof.
In the field of spectacle lens edge machining, the aim of which is to finish-machine the edge of a spectacle lens in such a way that the spectacle lens may be inserted into a spectacle frame, a trend has recently begun to emerge for this demanding machining to be relocated away from the opticians' workshops to the spectacle lens manufacturers in particular for reasons of rationalisation. When carried out by the spectacle lens manufacturers, this procedure requires spectacle lens machining machines, also known as “edgers”, which may quickly edge-machine the widest possible range of spectacle lenses with the required precision without much effort being required for setting up and may be used reliably for long periods.
DESCRIPTION OF THE PRIOR ART
In the prior art, there is no shortage of proposals for speeding up the edge-machining of spectacle lenses. For instance, the generic EP-A-0 917 929 discloses an edger for spectacle lenses which, to increase efficiency during machining, comprises two tool posts which are arranged parallel to the vertically extending axis of rotation of the spectacle lens to be edge-machined and are each provided with a set of grinding wheels. The one set of grinding wheels comprises a rough-grinding wheel and an intermediate grinding wheel provided with various grooves for beveling, while the other set of grinding wheels comprises a similar rough-grinding wheel and a finish-grinding wheel provided with beveling grooves for finishing. For each tool post there is provided an (X-Z) compound slide arrangement, with a vertical slide and a horizontal slide. On one side, the vertical slide is guided displaceably in the vertical direction on a machine frame while, on the other side of the vertical slide, the horizontal slide is guided displaceably in the horizontal direction. On the side remote from the vertical slide, the horizontal slide bears the respective tool post. By means of CNC-controlled slide drives, each tool set may be moved in a radial direction relative to the spectacle lens to be machined and parallel to the axis of rotation of the spectacle lens. The spectacle lens to be machined is clamped between two coaxial spectacle lens holding shafts, of which the lower spectacle lens holding shaft is arranged stationarily while the upper spectacle lens holding shaft can be moved relative to the lower spectacle lens holding shaft only in the direction of the workpiece axis. Finally, a CNC-controlled rotary actuator is provided for each spectacle lens holding shaft, such that the previously known edger is controlled in altogether 6 CNC axes. The rotary actuators are CNC-coupled for simultaneous rotation of the spectacle lens to be machined.
A spectacle lens edge grinding machine has also been proposed for speeding up edge-machining of spectacle lens (U.S. Pat. No. 4,179,851, DE-A-34 18 329), which, reversing the above conditions, has a grinding wheel set which is rotatable about a horizontally extending axis of rotation but is otherwise stationary. Moreover, this machine comprises two pairs of coaxial spectacle lens holding shafts for simultaneous edge-machining of two spectacle lenses, which holding shafts are oriented parallel to the axis of rotation of the tool. An (X-Y) cross slide arrangement is associated therein with each pair of spectacle lens holding shafts, such that the respective spectacle lens clamped between the spectacle lens holding shafts and to be edge-machined may be moved in the radial direction relative to the grinding wheel set and parallel to the axis of rotation of the grinding wheel set.
Finally, DE-U-298 23 464 discloses a concept in which a conventional machining machine for shaping the left spectacle lens and a further conventional machining machine for shaping the right spectacle lens are linked together via a conveying means and a handling apparatus for accelerated production of the left and right spectacle lenses for a spectacle frame.
Edge-machining of spectacle lenses may in principle indeed be speeded up with the above-described known methods. However, for industrial use, in which it is also necessary to machine relatively large numbers over relatively long periods without problems arising with regard to machining quality, the known methods appear to be suitable to only a very limited extent, in particular with respect to their mechanical structure.
For the sake of completeness, it should also be mentioned in this context that the prior art also includes proposals to provide an additional tool on a spectacle lens edger, which tool serves to form channels on the periphery of the shaped spectacle lens or bores or grooves in the spectacle lens and/or to bevel or chamfer the edges of the spectacle lens. This additional tool renders it unnecessary to transfer the spectacle lens to or reclamp it in a further machining machine and in this respect also speeds up edge-machining. In this context, methods are known in which (1) the additional tool is stationary with regard to the main tool, which may be moved in two mutually perpendicular directions by means of a compound slide arrangement, and is driven by the rotary actuator of the main tool (DE-A-43 08 800), (2) the additional tool may be swiveled relative to a stationary main tool from a rest position into a machining position, in order to enter into drive connection with the main tool and into machining engagement with the spectacle lens (EP-A-0 820 837), as are methods in which (3) the additional tool, provided with its own rotary actuator, may be swiveled relative to a stationary main tool from a rest position into a machining position, in order to come into machining engagement with the spectacle lens (DE-A-198 34 748).
SUMMARY OF THE INVENTION
The object of the invention is to provide a device of the simplest possible, compact construction for edge-machining an optical lens, in particular a spectacle lens, which meets industrial requirements with regard to throughput and machining quality.
According to one aspect of the present invention, there is provided a device for edge-machining an optical lens, which may be clamped between two aligned holding shafts rotatable about a rotational axis of a workpiece, having a first slide, which is guided longitudinally displaceably on a base frame in a first direction parallel to the rotational axis of the workpiece, and a second slide bearing a tool post with an edge-machining tool for the optical lens, which slide is guided longitudinally displaceably on the first slide in a second direction perpendicular to the first direction in such a way that the edge-machining tool may be brought into machining engagement with the optical lens; wherein the base frame is of substantially O-shaped construction and surrounds the first slide, and wherein the first slide is likewise of substantially O-shaped construction and surrounds the second slide. In other words, the slides are nested telescopically inside one another relative to one another and to the base frame, respectively, in an open rectangular frame construction.
According to a second aspect of the present invention, there is provided a device for edge-machining an optical lens, which may be clamped between two aligned holding shafts rotatable about a rotational axis of a workpiece, having a fir

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