MXPA99008961A - Method and apparatus for polishing oftalmi lenses - Google Patents

Abstract

The invention relates to an improved method, to a polishing tool head and to an apparatus for polishing lenses to carry out the method, to polish ophthalmic lenses, the apparatus has a polishing tool head, a flexible membrane that covers a polishing portion of the tool head, and pumps and cordless nozzle pump abrasive greasy paste on the polishing tool head, the new method consists of the conventional step of imparting an oscillating movement to the polishing tool head and contacting the lens surface with the polishing portion of the polishing tool head while an abrasive greyish paste is pumped over the polishing tool head, the improvement comprises the additional step of periodically corrugating the membrane to impart a wave in that membrane so that the abrasive gouache can flow between the membrane and the surface of the lens, the abrasive greasy paste moves in an efficient way over all a lens surface to improve the quality of polished lenses by this procedure

Description

METHOD AND APPARATUS FOR POLISHING OPHTHALMIC LENSES FIELD OF THE INVENTION This invention relates to the polishing of ophthalmic lenses, and more particularly, it relates to a method and apparatus for polishing ophthalmic lenses, using a polishing tool having a dynamically formable polishing membrane.

BACKGROUND OF THE INVENTION A principal requirement in the optical industry in connection with ophthalmic lens polishing apparatus is the ability to improve the surface finish of a lens without changing the curvature of the lens surfaces. Ideally, a lens polishing operation is limited to the removal of small cracks and machine marks on a lens while perfectly maintaining the prescribed bends. It will be appreciated that any point of uncontrolled pressure in a polishing membrane of a polishing tool head, or the depletion of polishing paste at any location on the membrane can cause the polishing operation to remove more or less material in a region of lens, thereby changing the prescribed curvature of that lens and causing optical defects.

Many types of lens polishing devices have been developed in the past and were used with varying degrees of success. These devices are believed to belong to two broad groups. The first group uses a polishing tool head having an elastic or flexible polishing membrane which is deformable on contact with the surface of a lens to adapt to the curvature of the lens. The examples of apparatuses belonging to this first group are described in the following US Patents: US Patent E.U.A. 3,589,071 of June 29, 1971 to Hans S. Hirschhom; Patent E.U.A. 5,205,083 of April 27, 1993 to Dennis R. Pettibone; U.S. Patent 5,662,518 of September 2, 1997 to Michael D. James et al. The second type of lens polishing apparatus of the prior art uses a plurality of plungers to apply pressure gradients on a lens polishing membrane. Although these devices are designed to polish mirrors of large telescopes, this is the type of apparatus that is of interest in the present. Examples of these apparatuses are illustrated in the following patents of E.U.A .: E.U.A. 4,606,151 of August 19, 1986 to Erich Heynacher; E.U.A. 4,802,309 of February 7, 1989 to Erich Heynacher; E.U.A. 4,850,152 of July 25, 1989 to Erich Heynacher et al. The latter examples describe polishing apparatuses having a plurality of actuators for applying different pressures in different areas of a polishing membrane. The different pressures are adjusted according to the amount of material to be removed at different locations on the lens surface, such that a polishing operation is carried out more quickly. These devices have undeniable merits and are believed to be great advances in the polishing of optical surfaces. However, these apparatuses do not face the fact that a lens polishing operation is normally accompanied by the accumulation or depletion of abrasive waxy paste in certain regions of the lens surface, which causes more or less polishing in those regions. Although this is a very common source of optical defects in ophthalmic lenses, there is no known prior art apparatus that offers a solution for controlling the movement of the abrasive waxy paste between a polishing membrane and a lens surface.

BRIEF DESCRIPTION OF THE INVENTION In the present invention, however, a new method for polishing an ophthalmic lens is provided. A polishing tool head is also provided which is adapted to conform simultaneously to the shape of an ophthalmic lens and to move abrasive greasy paste between the membrane thereof and the ophthalmic lens being polished. Broadly, according to a feature of the present invention, an improved method for polishing an ophthalmic lens surface using an apparatus having a polishing tool head is provided., a flexible membrane that covers a polishing portion of that tool head, and pumping means and nozzle for pumping abrasive greasy paste onto the polishing tool head. The new method consists of the conventional step of imparting an oscillating movement to the polishing tool head and contacting the surface of the lens with the polishing portion of the polishing tool head while an abrasive slurry is pumped over the head of the polishing tool and over the lens. The improvement consists of the additional step of periodically corrugating the membrane to impart a wave in that membrane in such a way that the abrasive gouache can flow between the membrane and the lens surface. A major advantage of this new method is that the polishing paste slurry moves efficiently over the entire surface of the lens to improve the quality of the polished lenses by this method. In another feature of the present invention, the new method also includes the step of forming the membrane together with a pair of right angle axes and defining membrane profiles along those axes that are respectively similar to and aligned with a base and curvatures crossed of the lenses being polished. This formation of the membrane ensures that a polishing operation is carried out uniformly without applying any pressure point or relaxed sector on the polishing portion of the polishing membrane. In a further feature of the present invention, a polishing tool head for polishing ophthalmic lenses is provided. The polishing tool head consists of a base plate having mounting means for securing same to a lens polishing apparatus, and a plurality of pneumatic accessories mounted on that base plate. A manifold plate is fixed to the base plate and has pneumatic circuits in it with each pneumatic circuit communicating with one of the pneumatic accessories. A plurality of pneumatic cylinders is fixed to the manifold plate, and defines a circular arrangement of cylinders aligned in parallel, with each cylinder being connected in a sealed communication with one of the respective pneumatic circuits. A rigid cover surrounds all the cylinders, and individually encloses a collar end of each cylinder, opposite to the manifold plate. An elongated sleeve immovably fixed to the cover in a central region of the circular arrangement, and being aligned with the cylinders, and a flexible membrane covering the cylinders and the cover are also provided. The membrane has a stem that extends from it and towards the sleeve and is secured inside the sleeve. Each cylinder has an extendable end that is movable against the flexible membrane to form the membrane.

When the pneumatic fittings are adapted to be connected to respective sources of air pressure, the cylinders are individually controllable to form the membrane in accordance with the curvatures of an ophthalmic lens. When the membrane is brought into contact with an ophthalmic lens, a central portion of the membrane is usable as a reference contact point to position the membrane against the ophthalmic lens with a selected pressure between the membrane and the lens surface. According to another characteristic of the present invention, the arrangement of cylinders in the polishing tool head consists of inner and outer concentric circles around the sleeve. Therefore, when the cylinders in each circle are periodically driven separately, the membrane is corrugated in circular waves to advantageously move the polishing greasy paste over the surface of the lens. In still another feature of the present invention, the cylinder arrangement is divisible into four diametrically opposed segments of the tool head, and the cylinders in each pair of opposite segments are operable in a group to generate radial waves in the membrane for the object of moving polishing paste on the surface of the lens. In still a further aspect of the present invention, the cylinder arrangement comprises two concentric circles. Each cylinder has an extendable end, and the extendable ends on the cylinders in the outer circle have D-shaped pads mounted thereon, with a short segment of the pad extending along a circumference of the circular arrangement, and each pad being pivoted on a respective extendable end, along an axis that is also aligned with the circumference of the circular arrangement. The extendable ends on the cylinders in the inner circle have cup-shaped suction lids mounted thereon. The suction caps are optionally connectable to a vacuum source as well as the cylinders in the inner circle. Therefore when the cylinders in the outer circle are connected to a pressure source and the cylinders in the inner circle and the suction caps are connected to a vacuum source, this cylinder arrangement is usable to form the membrane in accordance with curvature of extreme lenses. Yet another feature of the present invention is that the cylinder arrangement is a compact arrangement that is substantially similar to an area defined by a common ophthalmic lens preform. The arrangement of cylinders in mountable on a tool head having a common size and adaptable to conventional apparatus for polishing and burnishing lenses, to retrofit an existing lens polishing apparatus for example, thereby making such a polishing tool head economically available to the optical industry.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of this invention is illustrated in the appended drawings, in which like numbers denote similar parts throughout the different views, and in which: Figure 1 is a simplified illustration of an apparatus for polishing lenses in accordance with with the preferred embodiment of the present invention. For greater clarity, the apparatus is shown without the normal drive motor, control equipment, cabinets and other equipment common to this type of machines. Figure 2 is a side view of an ophthalmic lens mounted on a support block. Figure 3 is a close-up view of the polishing tool head comprised in the lens polishing apparatus. Figure 4 is a partial perspective view of the polishing station within the lens polishing apparatus. Figure 5 is a partial side elevation view of the lens polisher station. Figure 6 is an enlarged perspective view of the polishing tool head of the lens polisher station, with the cover membrane thereof shown in a cropped view. Figure 7 shows the polishing tool head without the cover membrane.

Figure 8 shows a plan view of the polishing tool head without the cover membrane. Figure 9 is a cross-sectional view through the polishing tool head as seen along the line 9-9 in Figure 8. Figure 10 is a plan view of the manifold plate incorporated in the base of the polishing tool head. Figure 11 is a pneumatic circuit diagram used in association of the polishing tool head. Figure 12 is a schematic illustration depicting an ideal trajectory of the polishing tool head on an ophthalmic lens. Figure 13 is a schematic plan view of the polishing tool head illustrating the different pressure zones therein wherein those pressure zones are operable in diametrically opposed sectors. Figure 14 is another schematic plan view of the polishing tool head illustrating the different pressure zones therein wherein the pressure zones are operable in concentric circles.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Although the invention is susceptible to embodiments in many different forms, it is shown in the drawings and will be described in the details herein, a specific embodiment of the apparatus according to the present invention and a method for the use of the apparatus, with the understanding that the present description should be considered as an example of the principles of the invention and is not designed to limit the invention to the illustrated and described mode. Reference will first be made to Figures 1, 2 and 3 respectively illustrating a simplified perspective view of the apparatus according to a preferred embodiment of the present invention, to carry out a new method for polishing ophthalmic lenses, an ophthalmic lens typical mounted on a support block, and a polishing tool head incorporated in the apparatus. However, before describing this apparatus in detail, it is considered that certain general information should be remembered in order to allow a clearer understanding of the diagram of Figure 1. The polishing of ophthalmic lenses referred to herein is refers to an optional step in the manufacture of ophthalmic lenses on an apparatus that generates ultra precision lenses wherein the final curvature of a lens surface is determined by a machining process and should not be altered during the polishing operation. The polishing of ophthalmic lenses is a light burnishing operation which is optionally carried out to remove invisible or hardly visible machine defects from the surface of the lenses, in order to produce lenses of a finer quality. The polishing of the lenses is carried out before applying an optional final clear resinous coating to the lenses. Accordingly, it will be appreciated that during such polishing operation, it is important to remove material from the surface of the lenses in a precise and controllable manner in order to obtain predictable results. This is, basically, the main purpose of the apparatus and the method according to the preferred embodiment. The apparatus according to the preferred embodiment consists in combination of: a washing station 20; a polishing station 22 and a robotic manipulator 24 for transporting an ophthalmic lens 26 with a lens block 28 fixed thereto from a positioning station (not shown) to the washing station 20; from the washing station 20 to the polishing station 22; and from the polishing station 22 back to the washing station and then to a laying station (not shown) where an operator can remove the lens 26 from the apparatus. It will be appreciated that the laying station (not shown) can be incorporated in the washing station, and that the lenses 26 and blocks 28 can be initially placed in the washing station 20 by an operator of the apparatus. The robotic picker 24 consists of a fastener assembly 40 for coupling and holding the lens block 28, and a pair of first and second linear actuators and sliding assemblies 42, 44 for moving the fastener assembly 40 in transverse and longitudinal directions respectively as indicated by the arrow 42 'and 44'. The robotic picker 24 is preferably also movable in upward and downward directions to hold and release a lens block 28. The lens 26 is preferably inserted in the washing station or in the lens positioning station (not shown) orienting manually a reference slot 50 with a corresponding indentation (not shown) in the workpiece holder of one of those stations. Referring again to Figure 1, the washing station 20 consists of a first vacuum piece holder 60 (similar to 80 in Figure 3) for retaining the lens block 28. The first vacuum piece holder 60 is mounted on the axis of a rotary actuator 62 in such a way that the lens 26 is rotatable during the wash cycle. Also provided is a wash container 64 mounted on a first structure 66 which is driven in up and down directions relative to the rotary actuator 62 by a third linear actuator and sliding assembly 68. The first vacuum piece holder 60 has a splash guard plate 70 movably adhered thereto, and a spray nozzle 72 is mounted inside the wash container 64. During the wash cycle, the wash container 64 is raised up against the splash cover plate 70 and it encloses the lens 26, the lens block 28 and the spray nozzle 72 completely. The water or a mixture of water and detergent is then roughened against the lens while the lens 26 rotates several times. Upon completion of the wash cycle, the lens 26 is transferred to the polishing station 22 by the robotic picker 24. The polishing station consists of a second vacuum piece holder 80 for holding the lens 26 during the polishing cycle. The second vacuum piece holder 80 is mounted above a polishing tool head 82 in such a way that the surface of the lens 26 to be polished faces downwardly facing the upper part of the polishing tool head 82. The second part holder vacuum 80 is mounted on a second structure which is only partially drawn to maintain the clarity of the drawing. The second structure consists of a fourth, fifth and sixth linear actuators and sliding assemblies 84, 86 and 88 respectively. These linear actuators and sliding assemblies are operable to move the second blank part holder 80 in three orthogonal directions indicated by the corresponding arrows 84 ', 86' and 88 '. Such movements of the second vacuum piece holder 80 are advantageous for initially positioning the geometric center of the lens to coincide with the vertical neutral axis of the polishing tool head 82, or for initially positioning the lens at a distance outside the nominal center relative to the neutral axis of the polishing tool head to accommodate a prism angle in that lens for example. It is also recommended to continuously move the lens 26 back and forth and from side to side in directions indicated by the arrows 84 'and 86' relative to the neutral axis of the polishing tool head during the polishing cycle to avoid over polishing or localized sub-polishing of the lenses. The second vacuum piece holder 80 and the polishing tool head 82 are preferably mounted within a sealable section 100. The section 100 preferably has a glass window 102, and the washing container 64 is preferably made of transparent material in such a manner that both operations can be supervised by an operator that stays close to the device. A continuous stream of polishing slurry is pumped onto the polishing tool head 82 and the lens 26 through one or more slurry nozzles as indicated by numeral 104 in Figure 3. The polishing tool head 82 of the apparatus is made operate in a circular oscillatory movement by a mechanism of the type described, for example, in U.S. Patent No. 5,175,961 of January 5, 1993 to Jhon R. Bolton. The rotating energy is applied to the mechanism in the pulley 106. With particular reference to Fig. 3, the vacuum piece holder 80 and the polishing tool head 82 are illustrated therein in a larger scale. The second vacuum part holder 80 is only partially illustrated therein. The partial illustration is also used to maintain the clarity of the drawing. However, it will be appreciated that this part holder 80, as well as the first part holder 60, are operated by a vacuum and are connected to a source of a vacuum and suitable control valves, via a conduit as illustrated and identified by the marking 110. In the apparatus according to the preferred embodiment, the vacuum holder 80 is mounted on a cardanic support 112, which in turn is mounted on a vertical strut 114 fixed to the sixth linear actuator 88. This preferred assembly it is better illustrated in Figures 4 and 5. The cardanic support 112 consists of a first C-shaped member 116 which is pivoted at its center along a first hinge axis 118 that passes through a first bearing ( not shown) in the vertical strut 114. A second C-shaped member 120 has its ends connected respectively to the ends of the first C-shaped member 116, along a second axis of articulation 122 perpendicularly. The first C-shaped member 120 has a flat surface 124 on an upper side thereof, as illustrated in Figure 5. This flat surface is advantageously used to selectively contact a spacer member 126 against the same. , for orienting and stabilizing the gimbal support 112 during the insertion of a support block 28 into the piece holder 80 or when removing a support block from the piece holder. In the preferred apparatus, the spacer member 126 is a circular member with flat ends mounted on the extension rod of a linear actuator 128.

Referring again to Figure 3, the polishing tool head 82 is preferably covered by a synthetic cap 130 that encloses the active part of it completely. The cloth cap 130 is held against the tool head by an elastic band 132 below the elongated portion of the tool head. The cloth material of the cloth cap 130 is selected such that it has good durability and good characteristics in relation to the absorption and retention of the slick polishing paste. A preferred type of fabric material for use in the manufacture of the fabric cap 130 is sold by DuPontT under the trade name Wearforcet "F". DuPont TM, E.l. Du Pont de Nemours and Company, have offices throughout the world with their corporate headquarters at 1007 Market Street, Wilmington, DE, 19898, U.S.A. It will be appreciated that, during the operation of the apparatus of the preferred embodiment, when the lens 26 is held against the polishing tool head 82 and when the abrasive water paste is pumped along the periphery of the lens, the central region of the lens 26 it may be devoid of an abundant circulation of watery paste, in comparison to the peripheral regions of the lens for example. It is known that the slurry has a liquid phase, usually water, and a solid phase consisting of microscopic abrasive particles, usually aluminum oxide particles, typically not more than five (5) microns in size. The object of the liquid phase is to bring the abrasive particles over the entire area to be polished, and to remove by means of washing the plastic or glass lens embracing particles. However, it will be appreciated that when the lens is in full contact with the polishing tool head, the slurry is not distributed evenly over the entire surface of the lens. This inconvenience can cause uneven wear of the cloth cap 130 covering the polishing tool head 82. The uneven distribution of the slurry across the entire surface of the lens can also cause uneven polishing of the lens. In order to avoid these polishing defects, the polishing tool head 82 of the preferred embodiment has a curved membrane 134, as illustrated in Figures 3 and 6, and a number of pneumatic cylinders 136 mounted under the membrane to form the membrane according to the curvature of the lens 26, and to maintain a uniform distribution pressure between the absorbent cloth cap 130, the membrane 134, and the total surface of the lens 26. The membrane 134 is preferably made of a flexible rubber material which is impervious to water, to prevent the watery paste from deteriorating the mechanism and the equipment associated with the pneumatic cylinders 136. The pneumatic cylinders 136 of the polishing tool head 82 according to the preferred embodiment perform the additional functions of periodically corrugating the Membrane 134 for moving the polishing wafer paste between the membrane and the lens 26. Referring now to FIGS. 6-11 at the same time, the head of polishing tool 82 of the apparatus of the preferred embodiment is described therein in greater detail. The polishing tool head 82 consists of eighteen (18) pneumatic cylinders 136 arranged in a circular or hexagonal arrangement around a central sleeve 138. The circular or hexagonal arrangement preferably has a diameter slightly smaller than a diameter of a standard lens proforma. . The arrangement of pneumatic cylinders 136 consists of two concentric circles; the outer circle has twelve (12) outer plungers 140 and the inner circle has six (6) inner plungers 142. In one version of the tool head 82, each pneumatic cylinder 136 is of the one-action type, returned by spring, mounted on collar, and the stroke length of each is selected so that it works in a region of half hit on it over the entire scale of adjustment of the polishing tool head. In this regard, the curvature of the membrane 134 of the polishing tool head of the apparatus according to the preferred embodiment is preferably adjustable from a slightly concave shape, of almost minus six (-6) diopters, to a flat configuration and a convex curvature of almost sixteen (16) diopters. The rod end of each outer plunger 140 has a D-shaped pad 144, in which the short segments define an arc along the circumference of the circular arrangement. Each D-shaped pad 144 is pivoted to the end of the rod on a pin 146 (in FIG. 9) through the rod end and extending along the aforementioned short segment. This configuration of the pads 144 is advantageous for working the membrane 134 over its entire active area, and especially along the circumference thereof. The rod ends of the internal pistons 142 preferably have caps 148 in the form of vacuum-type cups. The shape of these caps 148 is advantageous for applying a uniform distribution of pressure under the membrane when the pneumatic cylinders 136 of those pistons are driven outwardly. The shape of these cup-shaped lids 148 is also advantageous to optionally apply a vacuum thereto and a corresponding thrust force on the membrane to form the membrane in a flat configuration for example, or to corrugate the membrane to move watery paste to polished under it, as will be explained later. In the latter case, the pneumatic cylinders 136 operating the internal pistons 142 preferably have hollow rods communicating with a vacuum supply port, and are of the single-action, spring-extended type. It will also be appreciated that the internal pistons 142 with the caps 148 mounted thereto are also connectable to a vacuum source while their respective cylinders 136 are connectable to an air pressure source. In this configuration each cylinder has a vacuum and pressure port; the vacuum port being connected to a hollow plunger rod and the pressure port being connected to a piston outside that rod. This configuration, however, has not been illustrated by being common to persons skilled in the pneumatic system, and would be evident to those persons in light of the present specification. The central handle 138 is fixed in relation to the inner and outer pistons 140, 142. It has a longitudinal axis extending in a parallel alignment with the axes of the pneumatic cylinders 136. The handle 138 defines a neutral axis of the tool head 82. The central handle 138 has an interior dimension for receiving and supporting a stem 150 extending from the central region within the membrane 134. The stem 150 is firmly retainable within the handle 138 such that the stem 150 provides a point of reference to form the membrane according to the surface to be polished. The stem 150 is preferably made of flexible rubber, as for the membrane 134 itself, and is attached to or molded as an integral part of the membrane 134. The portion of the membrane near the stem 150 is positional against the lens, thus providing both a fixed base which is preferably kept in contact with the surface of the lens, and from which the membrane can be profiled to equalize the curvatures of the lens being polished. The portion of the membrane near the stem 150 also provides a reference point for moving the polishing tool head 82 against a lens to be polished, when a pressure measuring device is used to control the movement of the sixth linear actuator 88. A In this regard, the sixth linear actuator 88 preferably comprises a pneumatic linear actuator (not shown) that is connected to a high-precision adjustable pressure regulator (not shown). This pneumatic equipment in combination with the stem 150, allows the operator of the lens polishing apparatus to precisely set a basic pressure between the polishing tool head 82 and the surface of the lens to be polished. Referring now particularly to Figures 7, 9, and 10, the port end 152 of each cylinder 136 sits on a manifold plate 134 and is sealed in a respective recess in the manifold plate.

The manifold plate 154 and the pneumatic cylinders 136 are surrounded by a rigid cover 155. The cover also encloses a collar end of each pneumatic cylinder, as opposed to the manifold plate 154, for retaining those cylinders 136 in a spaced alignment and parallel. The handle 138 is also fixed to the cover 155 and extends in a parallel relationship with the cylinders 136. The cover 155 has one or more grooves 158 on the outer surface thereof to equal one or more similar ribs (not shown) within the membrane 134, and to index and retain the membrane therein. The manifold plate 154 has six (6) circuit grooves 156 thereon which connects one or more cylinders 136 to one of six (6) holes 158 that communicate with one of six (6) pressure supply accessories 160 that is extend from a base plate 162 to the tool head 82. The base plate 162 is mountable to the tool shaft of the oscillating mechanism by means of bolts through countersunk holes as illustrated. The six (6) circuit grooves 156 connect two or more cylinders 136 to form with the central stem 150, seven (7) pressure zones of the polishing tool head 82. Each zone is marked with a letter symbol from TV to 'G' as illustrated in Figures 8, 13 and 14. Each of the supply accessories 160 is connected to a pneumatic valve 164 operated by solenoid; which in turn is connected to a manifold 166 of air pressure supply. Provided on the supply port is the air pressure supply manifold 166, a pressure regulator 168 of proportional precision. The pressurization of each cylinder 136 is effected by operating a solenoid valve 164 at a time and changing the pressure setting of the pressure regulator 168 each time. The pressure regulator 168 is of the computer-controlled, rapid response type wherein the lock and pressurization of all six lines is effected in a very short time and in fact in a few seconds. The pressure in each cylinder 136 is preferably adjusted repeatedly throughout the period of operation of the polishing tool head. When the internal pistons 142 are used under vacuum, a similar circuit (not shown) is used to control the vacuum fixation in those pistons, in the caps 148 of those pistons or in the pistons 142 and the caps 148. With reference again to Figure 10, a seventh circuit groove 170 and a seventh hole 172 are shown on manifold plate 154.

This circuit groove is also connected to a pressure supply fitting 160 and to the manifold 166 of air pressure supply and to the regulator 168. The circuit groove 170 is connected to an access hole 174 through a central region of the tool head 82 as illustrated in Figure 9. The membrane 134 is preferably sealed around the cover 155, in the groove 176 by example as shown in figures 6 and 9. When air pressure is admitted through the conduit 174, this pressure is transmitted inside the tool head and under the membrane 134 to inflate the membrane. A light positive pressure inside the membrane is at the same time advantageous for reducing areas of concentration of pressure located in each plunger 140 or 142. Similarly, it will be appreciated that a vacuum can also be applied to the circuit groove 170 to obtain extreme curvatures in the membrane 134 for example. Referring now to Figure 12 the triple illustrations of the 'A' area on this drawing are representative of the travel of the central area of the tool head 82 during the polishing of a lens. While only the area 'A' is illustrated therein, the illustration is designed to describe the movement of the entire tool head 82 against the surface of the lens 26. The diameter and speed of the oscillatory movement is preferably adjustable. A satisfactory diametral setting on the apparatus of the preferred embodiment is between 10 to 20 mm and a preferred speed is between 300 and 600 cycles per minute for polishing a lens having a diameter of 75 mm. In order to better appreciate the performance of the polishing tool head 82, reference can now be made to Figure 13. This figure illustrates a plan view of the polishing tool head 82 and the seven regions defined by the stem 150 and the plungers 140, 142. The configuration of those regions is such that it is It is possible to group one or more zones to define four sectors as illustrated in this figure. Sectors 180 and 182 are opposite and symmetric. The sectors 184 and 186 are also opposite and symmetrical, and arranged at right angles to the sectors 180 and 182. The sectors 180 and 182 are arranged along the axis 188 of the cross curve of a lens to be polished on that head by example, hereinafter referred to as the cross-curve axis. Similarly, sectors 184 and 186 are disposed along the base curve axis 190. It will be appreciated that all areas on one side of the cross curve axis 188 are positioned symmetrically relative to other areas of the other. side of that axis. Similarly, the position of the zones on one side of the base curve axis 190 are symmetrical to the zones on the other side of that axis. Therefore, each zone of the polishing tool head is arranged in a symmetrical arrangement in four ways in relation to the whole of that zone with both orthogonal axes 188 and 190 of the polishing tool head. The advantages of this configuration of the pressure zones of the polishing tool head 82 will be more apparent in the light of the following description. The pressure settings of the pressure zones defined by sectors 180 and 182 are adjustable according to the shape of the cross curve of the prescribed lenses to be polished. Similarly, the pressure settings in the regions defined by sectors 184 and 186 are adjustable according to the shape of the base curve of the prescribed lens. The ability to create pressure gradients along two pairs of opposite sectors has shown that it is advantageous to form right angle profiles in the membrane 134 of the tool head 82 in accordance with basic curvatures of a lens 26, and therefore both get a smooth polishing of the lens surface. Another important feature of the polishing tool head 82 of the preferred embodiment is illustrated in Figure 14 and is also directly related to the symmetrical arrangement of the pressure zones on the tool head. The eighteen (18) pneumatic cylinders 136 of the tool head 82 are arranged in seven zones as mentioned above to form four (4) symmetrical sectors 180, 182, 184, 186. The seven zones are also configured to form three (3) ) concentric circles or three concentric hexagons. However, to maintain the clarity of the text, reference will be made to concentric circles. The first circle 192 forms a single zone * A? having a fixed stem 150. The second circle 194 consists of two zones, 'B and? ^ which respectively have four and two pneumatic cylinders 136. The third circle 196 consists of four zones \ * D \' and G 'which respectively have two cylinders, four cylinders, four cylinders and two cylinders. Each cylinder 136 in each of the zones 'B' to * G ~ is diametrically and symmetrically opposite from the other cylinder in the same zone.

The pressure in all the pneumatic cylinders along each circle 194 and 196, or the vacuum setting in the pistons 142 in the circle 194, can be periodically reduced from, or increased above, their prescribed settings, to make the membrane 134 deflects to controlled locations and to cause the membrane to ripple against the surface of the lens 26. The circular arrangements 194 and 196 are separately and sequentially operable to pump a nominal amount of abrasive gouache towards the center of the lens 26, or to expel watery paste from the central region of the lens towards the periphery of the lens. This controlled ripple of the membrane 134 and the pumping action created therein is advantageous for maintaining a constant supply of abrasive greasy paste across the entire surface of the lens. Because the zones in each circle are diametrically symmetrical in relation to the configuration of the polishing tool head, and because each zone can be operated for a specific length of time, the polishing effect of the tool head during the waviness of the membrane is controllable to ensure a uniform polishing action across the entire surface of the lens. It will be appreciated that the pumping action by crimping the membrane when pressing circular waves may be preferred by some users when the curvature of the membrane is close to a maximum value. When the curvature of the lens is almost flat, however, the pressure gradient in each pair of sectors 180-182 and 184-186 can alternatively be varied to generate pulsating radial waves in the membrane 134 and to corrugate the membrane 341 in a manner Sweeper type to take and spread abrasive greasy paste over the entire surface of the lens. It has been discovered that whether the membrane is corrugated periodically in a circular wave mode or in a radial wave mode, the efficiency of the polishing action is significantly improved. It will be appreciated that the pulsating wave action of the membrane is preferably imposed on the prescribed pressure settings for each cylinder. Therefore, the programmed curvature of the membrane 134 is always maintained before and after the formation of each wave and at the nodes of each wave. Although the pulsating effect described herein is known to greatly improve a lens polishing operation, those who are familiar with lens polishing procedures will appreciate that the pulsating effect described herein does not necessarily obviate completely the need to periodically raise the lens of the polishing tool head to renew the layer of polishing paste between polishing. As a more elaborate way of using and operating the apparatus according to the preferred embodiment, it should be evident from the aforementioned description, and accordingly an additional discussion regarding the manner of use and operation will be considered. redundant and therefore not provided. Although one embodiment of the present invention has been illustrated in the drawings appended and described herein above, it will be appreciated by those skilled in the art that various modifications, alternate constructions and equivalents may be used without departing from the real spirit and scope of the invention. the invention. Therefore, the above description and the illustrations should not be considered as limiting the scope of the invention which is defined by the appended claims.

Claims (20)

NOVELTY OF INVENTION CLAIMS

1. - An improved method for polishing an ophthalmic lens surface using an apparatus having a polishing tool head, a flexible membrane covering a polishing portion of said tool head, a pumping means and nozzle for pumping abrasive gouache onto the head of polishing tool; said method comprises the conventional step of: imparting an oscillatory movement to said polishing tool head and contacting the surface of the lens with the polishing portion of said polishing tool head while an abrasive slurry is pumped onto said polishing tool head and on said polishing tool head. lens, and wherein the improvement consists of the additional step of: periodically corrugating said membrane to impart a wave in said membrane in such a way that the abrasive waxy paste can flow between the membrane and the lens surface.

2. The method according to claim 1, characterized in that the tool head is circular and the step of periodically corrugating the membrane to impart a wave in said membrane consists of the step of imparting a radial wave in said membrane.

3. The method according to claim 1, characterized in that the tool head is circular and the step of periodically corrugating the membrane to impart a wave in said membrane consists of the step of imparting a circular wave in said membrane.

4. The method according to claim 1, characterized in that the polishing tool head has a neutral axis, and the method further includes the step of moving the ophthalmic lens surface back and forth and from side to side in relation to to said neutral axis.

5. The method according to claim 1, characterized in that the polishing tool head has a neutral axis, and said method further includes the steps of forming said membrane along a pair of right angle axes perpendicular to the neutral axis and forming profiles in said membrane along the axes, similar to a base and cross curvature of said lens respectively.

6. The method according to claim 5, characterized in that the profiles of the membrane are maintained before and after each wave, and at a node of said wave.

7. The method according to claim 5, characterized in that the step of forming said membrane includes the step of simultaneously pushing and pulling said membrane in relation to said polishing tool head.

8. The method according to claim 5, characterized in that the step of forming the membrane includes the step of slightly inflating said membrane.

9. - The method according to claim 5, characterized in that the step of periodically corrugating the membrane to impart a wave in said membrane consists of the step of continuously maintaining a portion of said membrane in contact with said ophthalmic lens surface.

10. A polishing tool head for polishing an ophthalmic lens, comprising: a base plate having mounting means for securing same to a lens polishing apparatus, and a plurality of pneumatic accessories mounted thereon; a manifold plate fixed to said base plate and having pneumatic circuits thereon with each of said pneumatic circuits communicating with an accessory in said plurality of accessories; a plurality of pneumatic cylinders fixed to said manifold plate, and defining a circular arrangement of cylinders aligned in parallel, with each of said cylinders being connected in a sealed communication with one of the respective pneumatic circuits; a cover that surrounds all the cylinders, and that individually encloses one end of each cylinder opposite to said manifold plate; an elongate sleeve fixed non-movably to said cover in a central region of the circular arrangement, and being aligned with said cylinders; a flexible membrane covering said cylinders and the cover, said membrane having a stem extending from the membrane towards the sleeve and being secured in said sleeve; and the cylinders each having a movable extendable end against the flexible membrane to form said membrane; such that when the fittings are adapted to be connected to respective sources of air pressure, said cylinders are individually controllable to form the membrane according to a curvature of an ophthalmic lens, and when said membrane is brought into contact with a lens Ophthalmic, a central portion of said membrane is usable as a reference contact point to position the membrane against the ophthalmic lens with a pressure selected between the membrane and the ophthalmic lens. 1.

The polishing tool head according to claim 10, characterized in that the cylinder arrangement consists of inner and outer concentric circles around said sleeve.

12. The polishing tool head according to claim 10, characterized in that the pneumatic circuits in said manifold plate consist of a circuit that communicates inside the membrane to inflate said membrane.

13. The polishing tool head according to claim 10, characterized in that said arrangement is divisible into two pairs of opposite segments therein and said pneumatic circuits are commonly connected to the pneumatic cylinders in each pair.

14. The polishing tool head according to claim 13, characterized in that the pneumatic circuits are also commonly connected to said pneumatic cylinders in each of said circles.

15. - The polishing tool head according to claim 10, characterized in that said extendable ends on the cylinders in the outer circle have a D-shaped pad mounted thereon, with a short segment of said D-shaped pad extending to along a circumference of said circular exposure, and said pad being pivoted on the extending end along an axis aligned with said circumference of said circular arrangement.

16. The polishing tool head according to claim 15, characterized in that the extendable ends in said cylinders in the inner circle have caps in the form of suction cups mounted thereto.

17. An apparatus for polishing an ophthalmic lens, comprising: a lens polishing station having a polishing tool head; means for imparting an oscillatory movement to said polishing tool head, means for retaining an ophthalmic lens in contact with said polishing tool head and against oscillatory movement; and means for pumping slurry polishing paste onto said polishing tool head; said polishing tool head has a flexible membrane mounted thereto and means mounted under said membrane to periodically corrugate said membrane; such that when the polishing tool head is adapted to be oscillated through a surface of an ophthalmic lens, when the polishing slurry is adapted to be pumped on said membrane, and when said membrane is adapted to be wavy periodically, said sharp paste is able to move between the membrane and the surface to effectively polish said surface.

18. The polishing apparatus according to claim 17, characterized in that the means for corrugation of the membrane consist of means for forming radial waves in said membrane.

19. The polishing apparatus according to claim 17, characterized in that the means for corrugation of the membrane consist of means for forming circular waves in said membrane.

20. The polishing apparatus according to claim 17, characterized in that the means for corrugation of the membrane consist of means for forming said membrane along a pair of perpendicular axes.