US3793774A

US3793774A - Apparatus for grinding inner and outer curved surfaces of a contact lens block simultaneously

Info

Publication number: US3793774A
Application number: US00233667A
Authority: US
Inventors: T Kawaguchi; I Mizutani
Original assignee: Toyo Contact Lens Co Ltd
Current assignee: Menicon Co Ltd
Priority date: 1972-03-10
Filing date: 1972-03-10
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26

Abstract

A method and an apparatus for grinding the inner and outer curved surfaces of a contact lens block simultaneously, wherein a member having a substantially spherical grinding head is used to grind the inner surface of the block, while a grinding abrasive having a desired contour is used to simultaneously grind the outer surface of the block, the abrasive being moved in a circle about the axis of rotation of the grinding member.

Description

United States Patent [191 Kawaguchi et al.

[ APPARATUS FOR GRINDING INNER AND OUTER CURVED SURFACES OF A CONTACT LENS BLOCK SIMULTANEOUSLY [75] Inventors: Toyohiro Kawaguchi; Isao Mizutani,

both of Nagoya, Japan [73] Assignee: Toyo Contact Lens Co., Ltd.

[22 Filed: Mar. 10, 1972 [21] Appl. No.: 233,667

52 user ..s1/117,51/217 L,51/120 [51] Int. Cl B24b 5/18 [58] Field of Search. 51/120, 284, 115, 111 R, 117, 51/118,119, 216 LP, 217 L, 88, 89

[56] References Cited UNITED STATES PATENTS 757,053 4/1904 Rameau 51/120 Feb. 26, 1974 2,587,926 4/1952 Touvay 51/284 X 3,274,737 9/1966 Rocher et a1..... 3,444,652 5/1969 Blum et al. 51/118 X Primary Examiner0t hell M. Simpson Assistant Examiner-Nicholas P. Godici Attorney, Agent, or FirmDonald Gunn I 57] ABSTRACT A method and an apparatus for grinding the inner and outer curved surfaces of a contact lens block simultaneously, wherein a member having a substantially spherical grinding head is used to grind the inner surface of the block, while a grinding abrasive having a desired contour is used to simultaneously grind the outer surface of the block, the abrasive being moved in a circle about the axis of rotation of the grinding member.

6 Claims, 3 Drawing Figures PATENTEDFEBZG'H" 3.193.114

PRIOR ART PRIOR ART 1 APPARATUS FOR GRINDING INNER AND OUTER CURVED SURFACES OF A CONTACT LENS BLOCK SIMULTANEOUSLY BACKGROUND OF THE INVENTION This invention relates to a method and an apparatus for grinding a contact lens block, and more particularly to a method and an apparatus for grinding the-inner and outer curved surfaces of a contact lens block simultaneously.

In the conventional method of grinding the inner and outer surfaces of a contact lens block, the grinding of the inner surface and of the outer surface have been done separately as schematically shown in FIGS. 1 and 2 respectively. This two step method has, therefore, required more time and a great deal of labor, hence making the product comparatively expensive. A further disadvantage of the old method results from the fact that a contact lens block is relatively thin. Consequently, a force appliedto only one side of the block during the old grinding operation, often distorts the block during the grinding operation, resulting in a high percentage of production rejects.

' SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an improved method of grinding a contact lens block which eliminates the aforesaid shortcomings of the conventional method. According to the method of this invention, the inner surface of a contact lens block is ground by means of a grinding ball which rotates in a predetermined directionabout a given axis. The contact lens block to be ground is mounted on the grinding ball, with its inner surface placed in contact with the ball, at an angle with respect to the axis of ro-' tation of the ball, and caused to rotate in precession about the rotating axis of the ball at a velocity lower than that of rotation of theball. Simultaneously with the grinding of the inner surface, the outer surface of the block is ground by means of an abrasive chip which is adapted to rotate around the axis of rotation of the grinding ball in a direction opposite to that in which the ball rotates.

The invention is further summarized as including an improved apparatus for grinding the inner and outer surfaces of a contact lens block simulanteously. The apparatus according to the invention comprises a rotary grindingmember which has a substantially spherical grinding head and which is adapted to rotate in one direction and grind the inner curved surface of a contact lens block carried thereon; a revolving needle fitted through the inner ring of a pillow block and bearing and adapted to reciprocate up and down while moving in a circle about the axis of rotation of the rotary grinding member in a direction opposite to that of rotation of the member; and an abrasive chip rotatably carried by the revolving needle contacting the outer curved surface of the block and adapted to move in a circle together with the revolving needle.

. BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the apparatus according to this invention will now, be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view illustrating the conventional method of grinding the inner curved surface of a contact lens block;

FIG. 2 is a view similar to FIG. 1, and-illustrating the conventional method of grinding the outer surface of the block; and

FIG. 3 is a view illustrating a preferred embodiment of the apparatus according to this invention which is adapted for the simultaneous grinding of both the inner and the outer surfaces of a contact lens block.

In the preferred embodiment of the apparatus according to this invention as shown in FIG. 3, a spindle 1 is connected to a motor 2 mounted on the base structure (not shown) of the apparatus, and is adapted to be rotated by the motor 2 counterclockwise. At its top, the spindle supports and rotates a removable rotary grinding member 3 having a substantially spherical grinding head or ball.

A pulley 4 is rotatably supported on a set of bearings 6 which are disposed in a bracket 5. The pulley 4 is adapted to be rotated clockwise around the same axis of rotation as that of the grinding member or ball 3 by means of a belt 7 connected to an appropriate power source (not shown) mounted on the base structure of the apparatus.

A sleeve 8 is supported upright from the pulley 4 but it is located at a center somewhat spaced from the center of the pulley 4. A revolving needle 9 is vertically slidably inserted in the sleeve 8, and is urged downward by its weight, by means of a spring, or the like. The inner ring of a pillow block and bearing assembly 11 slidably surrounds the lower part of the revolving needle 9, while the outer ring of the pillow block and bearing assembly 11 is fixed at the upper end of a central bore 12 made through a planetary body 10. Fixed to .the lower end of the hole 12 is a ring 13 formed with a flange extending along the upper inner edge thereof. The ring 13 is formed of a comparatively hard material, such as bakelite.

A substantially circular contact lens block L is mounted within the ring 13 with its inner curved surface facing downward so that it can be rotated from underneath. An abrasive chip 14, which is contacted against the outer curved surface of the block L, has a small hole in the center of the upper surface thereof, and the lower tip of the revolving needle 9 is inserted in that hole and bears on the abrasive chip 14, thereby securing and holding the chip 14 in contact with the lens block L. Thus, the central axis C C, of the contact lens block L is disposed at an angle to the axis C -C of rotation of the grinding ball 3. It will be noted that the contactlens block L is supported on the grinding ball 3 at the inner curved surface thereof.

The grinding chip incorporates a generally disc shaped backing and has a face for contact against the block L. The face, in conjunction with an abrasive, grinds and smooths the lens block L.

Reference will now be made to-the method of grinding a contact lens block by using the apparatus as hereinabove described. The planetary body 10 and the revolving needle 9 are raised to allow the mounting of a contact lens block L on the grinding ball 3. The inner surfaceofthe block L is coated with an abrasive. and placed on the ball 3. The outer surface of theblock L is also coated with an abrasive material, and abrasive chip 14 is positioned thereon. Preferrably the abrasive is applied in the described manner although it may be incorporated in the

respective grinding surfaces

3 and 14. Then, the revolving needle 9 is lowered to a position where its lower tip is engaged with the center hole of the grinding chip 14. The needle 9 is engaged with the planetary body 10 which engages contact lens block L loosely fitted within the positioning ring 13. The block L is thus interposed between the chip 14 and the grinding ball 3, and is ready to be ground thereby. The grinding ball 3 is rotated counterclockwise by the motor 2,and at the same time, the pulley 4 is rotated clockwise by the driving mechanism mounted on the base structure. As the pulley 4 rotates, the revolving needle 9 eccentrically located on the pulley 4 revolves clockwise in a circle around the axis of rotation of the grinding ball 3. As the grinding ball 3 rotates, it grinds the inner curved surface of the block L, and at the same time, the frictional resistance developed between the grinding ball 3 and the block L tends to rotate the block L in the same direction as the ball 3.

As the block L is thus rotated counterclockwise at a rate lower than the grinding ball 3, the frictional resistance developed between the circumferential area of the block L and the positioning ring 13 causes the planetary body 10 to rotate at a still lower speed in the same direction. Simultaneously, the revolution of the needle 9 causes the grinding chip 14 to revolve clockwise along a circular path, thereby enabling the chip 14 to grind the outer curved surface of the block L in a pre cessional motion. More particularly, the grinding chip 14 is rotated counterclockwise about the lower tip of the revolving needle 9, while grinding the outer curved surface of the block L because of the difference in the speed of rotation between the central and the outer circumferential portions of the block L. At the same time, the clockwise rotation of the needle 9 imparts to the planetary body 10 and the block L a precessional movement around the central axis of the grinding ball 3 so that the grinding ball 3 can grind the inner curved surface of the block L. Thus, as the result of the threedimensional or planetary movement of the contact lens block L and the grinding chip 14, together with the planetary body 10, the inner and outer curved surfaces of the block L are simultaneously ground by the grinding ball 3 and the grinding chip 14 respectively.

In the embodiment of the method according to the invention as hereinabove described, the grinding of both the inner and the outer surfaces of the block L has simultaneously been caused by the planetary motion of both the block L and the grinding chip 14. If desired, however, the contact lens block L alonemay be put into a planetary movement to achieve the simultaneous grinding of its inner and outer surfaces. It has been found, however, that the grinding operation can be faster and more effectively accomplished when both the contact lens block 1. and the grinding chip 14 are given a planetary movement.

It will thus be noted from the foregoing description that the grinding method according to this invention eliminates the drawbacks of the conventional time- .consuming two-step grinding operation because it permits simultaneous grinding of the inner and outer surfaces of a contact lens block by grinding means such as a grinding ball and a grinding chip positioned to maintain their frictional contact with the two surfaces of the block, while the block is given a planetary movement by means of a planetary traveling body or the like. It will also be observed that since the grinding force is applied to bothsides of the block simultaneously, and not to only one side as in theprior art, virtually no distortion or warpage of the block can occur, and rejects are reduced. Furthermore, since the planetary movement of the planetary traveling body and the grinding chip ensures a faster and more efficient grinding operation that has been possible in the prior art, the apparatus according to this invention permits production of contact lens blocks of highly acceptable quality with a markedly increased efficiency.

We claim: I

1. Apparatus for grinding the inner and outer curved surfaces of a contact lens block simultaneously, comprising: 4

first grinding means adapted to contact and grind the inner surface of a contact lens block;

second grinding means adapted to contact and grind the outer surface of such a block;

first means for rotating said first grinding means about a first axis;

an encircling ring means about such a lens block in contact with at least a portion of the periphery of the block;

second means including v a rotatable elongate means-positioned parallel to but spaced from the first axis;

a sleeve means positioning said elongate means for rotational and axial movement relative thereto; means for moving said sleeve in a generally circular pattern; and, said second means rotating said second grinding means in precessional movement of said second grinding means on the lens block by imparting movement to said second grinding means from said elongate means which is connected thereto and which rotates said second grinding means and simultaneously moves up and down dependent at least in part to the relative angular position of said ring means to the first axis.

2. The apparatus of claim 1 wherein said second grinding means includes a grinding surface having a back side, and means on the back side pivotally connected to said elongate means.

3. The apparatus of claim 2 including a generally hollow fitting for receiving said ring means therein and wherein said grinding surface within.

4. The apparatus of claim 3 wherein said hollow member is open at the top to enable said elongate means to extend thereinto.

5. The apparatus of claim 4 wherein said elongate means is free to reciprocate upwardly and downwardly relative to said hollow member.

6. The apparatus of claim 3 wherein said sleeve means is aligned above said hollow member and said elongate member passes through both.

' 8 t I I t

Claims

1. Apparatus for grinding the inner and outer curved surfaces of a contact lens block simultaneously, comprising: first grinding means adapted to contact and grind the inner surface of a contact lens block; second grinding means adapted to contact and grind the outer surface of such a block; First means for rotating said first grinding means about a first axis; an encircling ring means about such a lens block in contact with at least a portion of the periphery of the block; second means including a rotatable elongate means positioned parallel to but spaced from the first axis; a sleeve means positioning said elongate means for rotational and axial movement relative thereto; means for moving said sleeve in a generally circular pattern; and, said second means rotating said second grinding means in precessional movement of said second grinding means on the lens block by imparting movement to said second grinding means from said elongate means which is connected thereto and which rotates said second grinding means and simultaneously moves up and down dependent at least in part to the relative angular position of said ring means to the first axis.

3. The apparatus of claim 2 including a generally hollow fitting for receiving said ring means therein and wherein said grinding surface fits within.