US3769755A

US3769755A - Lens cutting and bevel edging machine

Info

Publication number: US3769755A
Application number: US00169634A
Authority: US
Inventors: A Kania; J Jerominek
Original assignee: Gentex Corp
Current assignee: Gentex Optics Inc
Priority date: 1971-08-06
Filing date: 1971-08-06
Publication date: 1973-11-06
Anticipated expiration: 1990-11-06
Also published as: FR2149925A5; GB1347828A; DE2234454A1; JPS4826152A; AU4383472A; AU453085B2; CA950201A; JPS534277B2; IT963585B

Abstract

Apparatus for cutting a curved lens blank to a predetermined shape while forming the edge thereof with a vee the apex of which is always at the center of the blank edge and the apex of which is located in the horizontal plane of the blank in which the blank to be cut is rotated relative to a rotating vee cutter at a fixed location while being supported for vertical movement and for horizontal movement relative to the cutter with the vertical movement of the blank being controlled by a cam surface having the same curvature as the blank and being centered on the cutter axis and the horizontal movement of the blank being controlled by a cam having the shape of the configuration to be cut.

Description

PATENTEU HUV B 1975 SHEET 3 UF 3 H T TORNEVS LENS CUTTING ANI) BEVEL EDGING MACHINE BACKGROUND OF THE INVENTION In recent years plastic materials have been used increasingly for the manufacture of various lenses. Allyl diglycal carbonate has been cast into ophthalmic lenses. Molded acrylic lenses have been relatively widely used in sunglasses. Polycarbonate, owing to its high impact resistance, is an excellent material for use in protective eyewear, such as safety goggles. Consideration is also being given to the use of these latter two resins in ophthalmic lenses. y

Lenses foruse in safety goggles and sunglasses and the like, as well as ophthalmic lenses, must be made in a variety of shapes and to a number of base curves where the base curve is the spherical radius defining the spherical section of the lens structure. For example, most safety and sunglases are` 6-base, which ymeans that the blank from which the lens is made has a radius of 88.3 mm. For other glasses, such as face form" and sweptback sunglasses, other bases are used. An 8- base has a radius of 66.2 mm. while a 12-base lens has a radius of 44 mm.

Where a large number of lenses are to be made to the same size and shape, molding is the preferred means of forming the lens. It will be appreciated, however, that' the cost of the mold is high, so that it is not feasible economically to make injection molds to produce both right and left lenses for a multiplicity of sizes, shapes and curves.

Metal and plastic spectacle and sunglass frames of the prior art are formed with grooves in the eye-wires for retaining the lenses in position on the frame. Usually the groove is a vee-shaped groovevwhich is milled into the frame prior to shaping and accepting the lens.

Most sunglass lenses presently being manufactured are merely cut from a largefblank having the thickness of about l mm. Lenses of this type may be more or less securely retained in the vee-groove of the frame. However, better quality lenses which are thicker than the cheaper lenses cannot adequately be retained in the spectacle frame unless the edge of the lens itself is beveled so as to mate with the vee of the frame. Recent regulations and proposed regulations to be promulgated by the authorities indicate that higher quality lenses in sunglasses Iand the like will be required for the future.

The procedure employed in the prior art to form high quality lenses from relatively thick blanks and with beleved edges forming a vee edge is a relatively expensive procedure. First, a blank is cut to the approximate shape and then is ground to the final lens contour on an abrasive wheel. The beveling usually is accomplished as a hand finishing operation. If a multiplicity of lenses of the same shape having beveled edges are to be produced, specially designed camming mechanisms are required for use in conjunction with wet grinding wheels to evolve the proper shape and to apply the necessary bevel.

While lenses can be produced from allyl diglycal carbonate using the technique described above, the cost of providing the equipment to achieve significant production capacity for a wide variety of shapes and curvatures is extremely high. Moreover, this method is not satisfactory for producing lenses from acrylic and polycarbonate resins since, owing to the nature of the process, and of the materials, the lenses are easily marred.

Summary of the Invention One object of our invention is to provide machine for simultaneously cutting a lens to shape while forming a vee on the edge thereof. y

Another object of our invention is to provide a lens cutting and bevel edging machine which permits high quality lenses to be formed at less cost than in the prior art.

A further object of our invention is to provide a lens cutting and bevel edging machine which operates satisfactorily on a wide variety of materials.

A still further object of our invention is to provide a lens cutting and bevel edging machine which is readily adjustable to cut lenses to a wide variety of shapes.

Still another object of our invention is to provide a lens cutting and bevel edging machine which can cut lenses to av relatively wide range of sizes.

Yet another object of our invention is to provide a lens cutting and bevel edging machine which is capable of cutting lenses of different bases.

A still further object of our invention is to provide a lens cutting and bevel edging machine which is relatively inexpensive to construct.

Other and further objects of our invention will appear in the following description.

In general, our invention contemplates the provision of a lens cutting andbevel edging machine in which the lens blank, while being rotated, is supported for vertical movements and for horizontal movement relative to a rotating vee cutter with the horizontal movement being controlledby a cam having the shape of the lens to be cut and with the vertical movement controlled by a spherical cam surface having a radius corresponding to the base of the lens to be formed.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the instant specifcaiton and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views: FIG. 1 is a schematic view illustrating a lens blank and the lens-shaping cam of our lens cutting and bevel edging machine.

FIG. 2 is a fragmentary-sectional view illustrating the vee edge of a lens formed on our lens cutting and bevel edging machine.

FIG. 3 is a side elevation of our lens cutting and bevel edging machine with some parts removed and with other parts broken away and with further parts in section.

FIG. 4 is a sectional view of our lens cutting and bevel edging machine, taken along the line 2-2 of FIG. 3 with parts broken away.

FIG. 5 is a top plan view of our lens cutting and bevel edging machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. l and 2 of the drawings, a lens l to be formed on our machine from a blank 12 having a certain base or spherical radius of curvature and adapted to be formed to a predetermined shape such as that indicated by a shaping cam 14 superposed on the blank 12 in FIG. 1. Cam 14 is provided with a mounting opening 16 and key slots 18, one of which receives a key to be described hereinbelow.

As has been pointed out hereinabove, in order that the lens l0 be securely held in a frame, the upper and lower edges of the blank 12 are beveled to form a vee 20 which is received in the vee-groove in the lens frame. If the lens l0 is to fit properly in the frame so as to be securely held therein, the vee 20 must bear a predetermined geometric relationship to the lens. That is, the base of the vee 20 must always be perpendicular to a line x-x perpendicular to the central axis of the lens 10. Further, all of the lines such as x-x must be located in a plane passing through the center of the cutting edge and perpendicular to the axis of the cutter. If the vee is so cut, it cannot easily be pushed out of the frame once it has been inserted therein. If the vee applied to the lens were at right angles to the radial plane, the structure would not provide angular retentionvin the case of a large lens or of a lens with a short radius of curvature.

Referring now to FIGS. 3 to 5, our machine includes a supporting table 22 on which a housing, indicatedA generally by the reference character 24, rests. The housing 24 may be formed as a generally rectangular casting from a suitable material such, for example, as an aluminum alloy. The housing 24 includes a base 26,

ends

28 and 30, and a top 32 provided with an opening 34. Any suitable means, such for example, as metal screws 36,/may be used to secure

side plates

38 and 40 to the housing 24.

The machine carriage, indicated generally by the reference character 42, may bein the form of a generally rectangular casting of an aluminum alloy providing a base 44,

ends

46 and 48 and a top 50.

Spaced guide rods

52 and 54 secured in position in the ends v28 and 30 of housing 24 by any suitable means such as by nuts 56, extend through bushings 58 in the ends .46 and 48 of the carriage 42 support the carriage for generally horizontal movement with'relation to the housing 24.

A hollow stand 60 resting on the table 22 houses a weight 62 secured to one end of a cable 64. The cable 64 extends upwardly through a cap 66 on the stand 60 and around a sheave 68 rotatably supported on a bracket 70 on the cap 66 by means of a pin 72.l We train the cable 64 around a second sheave 74 rotatably supported by a pin 76 carried by a bracket 78 mounted on the side of the stand 60. From the sheave 74 cable 64 extends through an opening 80 in the end 28 of housing 24 and through a bore 82 of a stop nut 84 screwed into an opening 86 in the end 46'of carriage 42. A knot 88 or the like retains the end of cable 64 in a recess 90 in the stop nut 84. From the structure just described, it will readily be apparent that the weight 62 normally urges carriage 42 to move to the left as viewed in FIG. 3. The limit of 'such movement is provided by engagement of stop nut 84 with the end 28 of the housing 24.

Respective bushings

92 and 94, positioned in the openings of

bosses

96 and 98 in the top 50 and in the base 44 of the carriage 42, slidably receive a shaft 100 for vertical movement relative to the carriage. The lower end of shaft 100 is provided with an axial bore which receives a stylus 102 secured in the bore by a set screw 104. The lower end of the stylus 102 carries a ball 106 adapted to engage a spherical cam surface 108 of a cam 110 secured to the base 26 of housing 24 by any suitable means such as clamps 112. As will be explained more fully hereinafter, the surface 108 has the same curvature as that of the lens to be cut and its center is positioned at the axis ofthe cutter to be described hereinafter.

Respective spacers 114 attached to the top 50 of the carriage 42 by screws 1 16 receive studs 1 18 on a motor 120 to support the' motor on the carriage 42 for move ment therewith. The motor shaft 122 carries a gear 124 which meshes with a gear 126 positioned on shaft 100 by means of a set screw 128. Motor 120 is a slow speed motor of about 2 r.p.m. so as slowly torotate the shaft 100 in the course of the cutting operation to be described hereinbelow.

Our machine includes a cutter or grinder 130 having a cutting surface 132 adapted to reduce the size of a blank such as the blank 12 while forming the vee 20 at the edge thereof. We mount the cutter 130 on the out-v put shaft 134 of a motor 136 by any suitable means known to the art. Motor 136 may be carried by a bracket 138 rextending from the upper portion of the stand 60, for example.

Our machine includes a lens holder 140 having a ceni trally-located bore 142 with an annular flange 144 at the lower endvthereof for receiving the outer ring of a radial bearing 146, the inner ring of which engages a shoulder 148 on the shaft 100. A spacer washer 150 spaces the radial bearing 146 from a thrust bearing 152 surrounding a bushing 154the upper end of which is formed with an outwardly extending annular flange 156.

We position agenerally cylindrical cam retainer 158 on the shaft above the thrust bearing 152. A square key 160 keys the retainer 158 to the shaft 100 for rotation therewith. A flange 162 at the lower end of the retainer 158 received the cam 14. A cap 164 secured to the upper end of shaft 100 by a screw166 holds the cam retainer 158 on the shaft. We position a lens blank support 168 over the retainer 158. The upper surface 170 of the support 168 has a curvature corresponding to that of the lens blank 12. Another square key 172 keys the cam 14 and the lens support 168 to the retainer 158 which, as is pointed out hereinabove, is keyed to the shaft 100. ltwill readily be appreciated, from the structure just described, that the carn 14 and the lens support 168 may readily be changed when either the shape of the lens or the curvature is tov be changed.

We form the lens support 140 with an upright 174 to which we secure a clamp bracket 176 by any suitable means such as by screws 178. The bracket 176 carries pinv 180 which pivot-ally supports a clamping arm 182. We thread a retaining bolt 184 in the end of arm 182 remote from the pivot pin 180. A nut 186 secures the bolt 184 in positon on the arm 182. We provide the lens clamp 188 with an under-surface 190 conforming to the upper surface of the blank from which the lens is formed. A recess 192 in clamp 188 receives a thrust washer 194. The lower end of bolt 184 is formed with a head 196 which engages a ball 198 restingv on the washer 194. A cover plate 200 secured to the clamp 188 retains the head 196, ball 198 and washer 194 in the recess 192.

A pin 202 pivotally connects arm 182 to a handle 204. A pin 206 pivotally connects one end of a link 208 to the bracket 176. Another pin 210 connects the other end of the link 208 to the handle 204. It will be appreciated that handle 204, arm 182 and like 208, make up a toggle clamp which, in the full line position of the parts shown in FIG. 4, clamps a blank between surface 190 and surface 170. To release the clamp, handle 204 is moved upwardly to the broken line position illustrated in FIG. 4.

From the structure thus far described, it will be apparent that when shaft 100 is driven by the motor 120 the assembly supported at the top thereof,vincluding the lens support 140, tends to rotate. We provide the support with a downward extension 21 1 carrying a stop roller 212 adapted to engage the side plate 40 to limit the amount of rotation of the support 140. Once the roller engages the plate 40, the cam 14 and the lens blank 12 are permitted to rotate with the shaft 100 relative to the support 140 by means of the ball 198.

We form the housing 24 at the upper left hand comer thereof as viewed in FIG. 3 with an integral bracket 214 providing a recess 216 bounded by two

sides

218 and 220. We secure a cam follower 224 in a recess in a follower carrier 222 by any suitable means such as by a screw 226. The follower 222 carries a block 228 on the underside thereof which extends into the recess 216 between

sides

218 and 220. A downward extension 230 on block 228 threadably receives a lead screw 232. A nut 234 on screw 232 and a washer 236 mount the lead screw 232 for rotary movement in an opening 240 in bracket 214. We provide the screw with a head 238 adapted to be turned to rotate the screw to move the follower carrier 224 back and forth with relation to the axis of shaft 100 and at a location at which it can engage the edge of cam 14. In this way, the size of the lens to be cut to a particular shape can be varied. Screws 242 and 244 extending through slots 246 and 248 in carrier 222 are threaded into the sides 218 and l220 to hold follower carrier 222 in the position to which it has been adjusted.

In use of our lens shaping and edging apparatus, we first select blanks 12, having the curvature which is to be provided in the finished lens. Next, we select a cam 1 10 having a cam surface 108 of a curvature which corresponds to the Acurvature of the blank 12. We mount the cam 110 on the base 26 of housing 24 with the setter of the cam surface 108 aligned with the axis of rotation of the tool 130. This tool is selected to have a working surface 132 such as will form the desired vee edge on the blank 12.

When the proper cam 110 has been mounted on base 26 by means of the clamps 112, we next select a cam 14 having an outline configuration corresponding to the shape of the lens'to be cut. In order to position the cam on the shaft, handle 204 is in a position at which clamp 188 is released. The lower lens clamping element 168 is removed from shaft 100 and the cam 14 is placed on the shaft with one of its slots 18 receiving key 172. Next, we select a lower clamping element 168 the surface 170 of which has a curvature corresponding to that of the undersurface of the blank 12 being worked on. This lower clamping element 168 is placed on the upper end of shaft with the key 172 being received in the slot in the wall of the element 168. We select an upper clamping element 188 having a curved surface 190 the curvature of which corresponds to that of the upper surface of the blank being worked on. This memberis secured to the bolt 184 by means of the plate 200 with the ball 198 clamped between head 196 and the washer 194.

Itvwill readily be apparent that the size of the cam 14 determines the size of the lens to be cut from the blank as well as the shape of the lens. Size adjustments, however, without changing the cam, can be made by adjusting the position of the follower carrier 222 on the bracket 214.

When the proper cams have been assembled on the apparatus in the manner described, and when the follower carrier 222 has been properly positioned, the machine is ready for operation. The tool motor 136 is en` ergized. Weight 62 moves carriage 42 to the left as viewed in FIG. 3 to bring the cam 14 into engagement with the follower 224. At the same time, motor 120 is energized to rotate shaft 100. As the shaft rotates the cam 14 controls the left and right movement of the carriage to govern the shape of the lens being cut. At the same time, ball '106 follows the contour of surface 108 to cause shaft 100 to move upwardly or downwardly so as to ensure that the apex of the vee 20 remains in the horizontal plane of the lens and at the center of the lens edge. It will vbe clear that as the carriage 42 moves to the left as viewed in FIG. 3, the blank 12 moves downwardly with respect to the working surface 132.

When one blank has been cut the clamp is released, a new blank is placed in position and its edge is brought into engagement with the working surface 132 and the operation proceeds as before. When lenses of a different shape but of the same basic curvature are to be produced, it is only necessary to change the cam 14. When blanks of a different base are to be shaped and edged, it is necessary to change cam as well as the upper and lower clamping elements 168 an'd 188 to those having a shape corresponding to the curvature of the blank. v

It will bese'en that wehave accomplished the objects of our invention. We have provided apparatus forf'simultaneously cutting a lens blank to shape while forming a vee round the edge thereof. Our machine enables us to produce highquality lenses at less cost than in the prior art. It operates satisfactorily on a wide variety of materials. Itis readily adaptedto cut lenses of a variety of shapes and of different curvatures. It is relatively inexpensive to construct for the result achieved.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations.

l This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. lt is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim 1. Apparatus for positioning a lens blank having'a known curvature relative to forming means for providing said blank with a certain outline configuration while forming the edge thereof to have a cross section of predetermined geometrical shapel including in combination, a lens blank support, means including a shaft mounting said support in operative relationship to said forming means, means mounting said shaft for rotary movement around its longitudinal axis and for rectilinear movement with respect to said mounting means in the direction of said axis, means supporting said shaft mounting means for rectilinear movement in a direction generally perpendicular to said axis, means for rotating said shaft, means responsive to rotation of said shaft for positioning said supporting means in said perpendicular direction, and means responsive to movement of said supporting means for positioning said shaft in said axial direction.

2. Apparatus as in claim 1 in which said means responsiveto said shaft rotation comprises interengageable cam and follower means, said cam having the shape of the lens to be formed from said blank.

3. Apparatus as in claim 2 including means for biasing said cam and follower means into engagement.

4. Apparatus as in claim 2 in which said means responsive to movement of said supporting means corriprises a cam surface having a curvature corresponding to that of said blank and a follower on said shaft for engaging said cam surface.

5. Apparatus as in claim 2 in which said means responsive to movement of said supporting means comprises first cam and follower means on said shaft and said carrying means for controlling the axial movement of said shaft and said means responsive to rotation of said shaft comprises second cam and follower means on said supporting means and on said shaft supporting means for controlling the transverse movement of said support.

6. Apparatus as in claim 5 in which said first cam has a spherical surface centered at the axis of said shaft and in which said second cam has an outlined configuration in the shape of the lens to be formed.

7. Apparatus for shaping a lens blank having a predetermined curvature to a certain outline configuration while forming the edge thereof to a vee cross section with the apex of the vee at the center of the lens edge and in the horizontal plane of the lens including in combination, a support, a tool having a working surface adapted to form a vee on the edge of a lens blank in response to rotation of said tool around its axis, a carriage, means mounting said carriage on said support for rectilinear movement in a direction generally transverse to said tool axis, a shaft, means mounting said shaft on said support for rotary movement around an axis generally parallel to said tool axis and for rectilinear movement in the direction of said shaft axis, means for supporting a lens blank on said shaft to permit the edge thereof to engage the working surface of said tool, first cam and follower means on said shaft and on said support for controlling the movement of said carriage transversely of said shaft axis and second cam and follower means on said shaft and on said support for controlling the movement of said shaft in the direction of said shaft axis.

8. Apparatus as in claim 7 in which said first cam means comprises a first cam carried by said shaft, said first cam having theoutline configuration of the lens to be formed, and a follower carried by said support.

9. Apparatus as in claim 8 including means for adjustably positioning said first cam on the support.

10. Apparatus as in claim 7 in which said second cam and follower means comprises a second cam on said support, said second cam having a curvature corresponding to that of the blank and centered at the axis of rotation of the cutter.

11. Apparatus as in claim 7 in which said first cam means comprises a first cam having the outline configuration of the lens to be cut, means mounting said first cam on said shaft for rotation therewith and a stationary follower carried by said support, and in which said second cam and follower means comprises a second cam carried by said support, said second cam having a curvature corresponding to that of said blank and centered on the axis of rotation of said cutter, and a follower on said shaft.

12. Apparatus as in claim ll including means for biasing said carriage to move in a direction to bring said first cam and follower into engagement.

Claims

1. Apparatus for positioning a lens blank having a known curvature relative to forming means for providing said blank with a certain outline configuration while forming the edge thereof to have a cross section of predetermined geometrical shape including in combination, a lens blank support, means including a shaft mounting said support in operative relationship to said forming means, means mounting said shaft for rotary movement around its longitudinal axis and for rectilinear movement with respect to said mounting means in the direction of said axis, means supporting said shaft mounting means for rectilinear movement in a direction generally perpendicular to said axis, means for rotating said shaft, means responsive to rotation of said shaft for positioning said supporting means in said perpendicular direction, and means responsive to movement of said supporting means for positioning said shaft in said axial direction.

2. Apparatus as in claim 1 in which said means responsive to said shaft rotation comprises interengageable cam and follower means, said cam having the shape of the lens to be formed from said blank.

4. Apparatus as in claim 2 in which said means responsive to movement of said supporting means comprises a cam surface having a curvature corresponding to that of said blank and a follower on said shaft for engaging said cam surface.

8. Apparatus as in claim 7 in which said first cam means comprises a first cam carried by said shaft, said first cam having the outline configuration of the lens to be formed, and a follower carried by said support.

12. Apparatus as in claim 11 including means for biasing said carriage to move in a direction to bring said first cam and follower into engagement.