1. Field of the Invention
The present invention pertains to an eyeglass end face machining method, particularly to the polishing to a mirror polishing that is performed on the end face after bevel edging, or the planing, such as machining to a mirror polishing, that is performed on the end face after edging.
2. Description of the Related Art
The lens end face of rimless eyeglasses lenses usually referred to as three-piece eyeglass lenses is exposed and not covered by a rim, etc., and therefore, they must have a surface that has been polished until glossy. In response to this need, technology has been presented whereby eyeglass lenses, whose end face has thus far been smoothed manually in order to obtain a face that has been polished until glossy, are mechanically polished by placing a movement mechanism with tracing capability in the polishing wheel part (for instance, Japanese Patent Laid-Open No. Sho 64-87144). This grinds inclined faces, such as the end face of polyhedron cut lenses, etc., and although the shape around the eyeglass lens is complex because of the polyhedron cut, the end face itself, which becomes the surface to be grounded, is a flat surface and simple. Consequently, the above-mentioned technology cannot be used when the surface to be polished itself has a complex shape, such as lens end faces with a bevel. Now, because the lens end face with a bevel is usually concealed by the rim of the frame and there is no need to polish the bevel faces, a lens end face with a bevel itself is usually not polished.
However, there has been a demand in recent years for thin rims in order to obtain frames that are more lightweight and fashionable, etc., and it is often the case that if the lens fitted into the rim is a strong-minus-power lens with a thick edge, the lens will protrude from the rim of the frame. It is pointed out that the bevel faces remains white when polishing of the lens end face is completed by bevel-polishing and this poses a problem aesthetically. Polishing the bevel surface that remains white until it is transparent is only accomplished by buff polishing the bevel surface by hand, etc., and this takes time and increases cost.
The objective of the present invention is to solve the above-mentioned problems with prior art by mechanically polishing the bevel faces in 2 steps and to present a lens end face machining method, wheel and device for eyeglass lens end face machining with which it is possible to speed up the polishing process and make finishing precision uniform and obtain fashionable eyeglass.
Moreover, in addition to the aesthetic problem of the lens end face remaining white after bevel polishing that was previously described, there is a problem with polishing precision and fashionable eyeglasses in that when planing, such as smooth machining and machining to a mirror polishing etc., is performed with a wheel that has a bevel-groove and a planing face, streaks are made. That is, cylindrical grinding stone called diamond wheels(stone) have a bevel-groove for formation of a bevel at the end face of the eyeglass lens and a flat face for flat machining the end face of an eyeglass lens. In further detail, the wheel has groove inclined face 301 for V finishing having a specific angle with respect to the axial direction called angle No. 1, flank 203 for the eyebrow of the frames continuous with this groove inclined face 301 having a specific angle with respect to the axial direction referred to as angle No. 2 that is smaller than angle No. 1, and flat finishing face 303 continuous with this flank 302 for flat machining and parallel to the axial direction on the surface around the periphery of the wheel. The inclination at boundary K between above-mentioned flank 302 and flat finishing face 303 is not continuous.
Consequently, when an eyeglass lens moves past boundary K to the left in the direction of the X axis during flat machining, apex A of the end face of eyeglass lens 6 straddles boundary K and a streak from boundary K is made in end face 6a of eyeglass lens 6. When a streak is made in end face 6a of the eyeglass lens, edging precision drops and becomes non-uniform, and the product is not fashionable. Therefore, such a streak is undesirable. This is particularly a problem with flat finished surfaces that remain white and are further given a mirror finish so that they are transparent.
Thereupon, in order to solve this problem, flat finishing face 303 is made longer in the axial direction so that even if eyeglass lens 6 moves to the left in the direction of the X axis during flat edging, it will not pass boundary K. However, there is a problem in that as a result, wheel 1 is larger.
Inerdentally there is a demand for mechanical polishing of the bevel face that remains white using a wheel as a means of solving the above-mentioned aesthetic problem of the lens end face remaining white after bevel polishing because buffing, etc., manually takes time and increases cost. However, there is also a problem when a polishing wheel is used with the existing wheel in that the device becomes bigger.
The objective of the present invention is to solve the above-mentioned problems of prior art and present an eyeglass lens end face matching method with which polishing precision is uniform, the product is excellent in terms of being fashionable, and the device can be reduced in size. Another objective of the present invention is to present an eyeglass end face machining method with which it is possible to add a polishing wheel that can give the eyeglass lens end face a mirror polish without greatly increasing length of the wheel in the axial direction.