Abrading – Machine – Rotary reciprocating tool
Reexamination Certificate
1999-06-10
2001-05-08
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary reciprocating tool
C451S005000, C451S210000, C451S255000, C451S256000, C451S277000, C451S323000
Reexamination Certificate
active
06227952
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a method for creating a concave surface from a rough blank for spectacles and tools for carrying out the method on brittle-hard and plastic blanks for eyeglasses.
BACKGROUND OF THE INVENTION
In a familiar method of the kind indicated at the outset (DE 42 10 381 A1), the tool and the workpiece are controlled during the entire process sequence so that the removal of material occurs exclusively along a spiral path. Although this method makes it possible to shape the concave surface, (which already largely conforms to the finished surface of the lens), this method provides poor cutting performance. If larger amounts of material are to be removed from the workpiece, the workpiece and tool have to be moved relative to each other many times along a spiral path, which results in undesirably long machining times when manufacturing eyeglasses by prescription.
SUMMARY OF THE INVENTION
Hence, an objective of the present invention is to provide a method for creating concave surfaces on a rough blank for spectacles by which it is possible to machine precisely and economically both brittle-hard materials and plastic materials with high cutting performance to produce all conventional concave surface shapes of spectacle optics, with the outcome of a uniform surface quality and short machining times. A further object of the present invention is to provide tools which are especially suitable for carrying out the method.
These and other objects and advantages are achieved by a method for creating a concave surface on a rough blank for eyeglasses (workpiece), by a milling or grinding tool, in which the blocked-up workpiece and the tool are moved relative to each other in a CNC-controlled machining process with two linear axes of motion (x and y axis) and two axes of rotational movement making an angle (∝) to each other: A first axis (the “b-axis”) is assigned to the workpiece and the other axis (the “c-axis”) is assigned to the tool. Removal of material to shape the surface is done along a spiral path on the surface, in that the tool and the workpiece are moved relative to each other along the x, y and b axes. A disk-shaped rotation-symmetrical tool is used as the tool and is arranged such that the lowest point of the tool in relation to the workpiece is situated in a plane defined by the b and x axes. Removal of material along the spiral path is preceded by a plunge-step, during which the workpiece rotates about its axis (b) and the tool is moved at least in the direction of the y-axis, until a surface in the shape of an annular trough is achieved, the concave surface being created at least in the region of the outer rim of the workpiece, so that the surface produced on the workpiece at least in the region of the outer rim corresponds to the nominal outer contour of the optically active inner surface of the eyeglass.
Dividing of the processing method into two work steps, namely , a first plunge-cut process and a second process with removal of material along a spiral path, results in very short machining times. In the plunge-cut step, very high cutting or grinding rates are possible, so that the main bulk of the blank material to be removed is quickly taken off. The continuous plunge or infeed step spares the multiple cuts which are necessary in the known technique in the case of a thick blank. Already during the plunge-cut, at least in the region of the outer rim, a surface is achieved which corresponds to the nominal outer contour of the optically-active inner surface of the eyeglasses.
The method according to the invention makes it possible to create high-precision surfaces for all conventional surface shapes of spectacle optics, namely, toroidal, prismatic, off-center, multifocal or nontoroidal surfaces on glass and plastics.
Preferably, a rim machining step is integrated into the method, whereby one can produce not only thin comfortable eyeglasses, but also shorten the work time for the later fitting of the eyeglasses into the frame with less wear on the tool on the part of the eyeglass maker. The user of the method has the advantage of a smaller inventory of semifinished glasses of different diameters. If the three work steps of rim machining, plunge-cut, and machining along the spiral path are undertaken in continuous sequence, very short production times can be achieved. These work steps can be carried out in a single clamping or blocking of the workpiece.
If the peripheral edge of the workpiece is supposed to be provided with a facet, it is also possible to incorporate a faceting step in the process sequence so that when undertaking a rim machining step a total of four immediately consecutive work steps are carried out with only one clamping or blocking of the workpiece.
A grinding tool for carrying out the method on a brittle-hard spectacle glass blank is very advantageous because of the special configuration of the grinding lip, since the blade geometry remains constant, even when undergoing wear. Only the diameter of the tool is reduced by wear, yet this can be easily compensated by measuring the thickness of the ground glass and then allowing for it in the control program.
A milling tool for carrying out the method on a plastic spectacle blank is disk shaped in respect of its form of rotation, and individual milling cutters are distributed about the periphery. The cutting performance of this milling tool, in which the blades define a toroidal envelope surface, is high. The lifetime of the milling cutters can be advantageously enhanced if the cutting plates of the milling tool containing the blades are mounted so that they can be rotated. In this way, several successive regions of the cutting plate can be twisted into a working position before the cutting plates have to be replaced on account of wear, or their outer diameter has to be touched up.
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Opposition letter of Messrs. Coburn Optical Industries Inc. dated Jun. 5, 1997 (Opponent III).
Affidavit of Raymond D. Gregory filed by (Opponent III).
The paper filed by applicant Loh Optikmaschinen AG on Nov. 5, 1998 in response to the three oppositions.
Bedeutung der Sonderwerkzeuge- Anwendungbeispiele für Serien mit mitteren Stückzahlen, Maschinenmarkt, Wurzbur, 82 (1976) 86, p. 1577-1580.
Diehl Joachim
Lautz Ronald
Tross Karl-Heinz
Hail III Joseph J.
LOH Optikmaschinen AG
McAndrews Held & Malloy Ltd.
Nguyen George
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