US3916574A

US3916574A - Lens surfacing apparatus

Info

Publication number: US3916574A
Application number: US528298A
Authority: US
Inventors: Louis Prunier
Original assignee: American Optical Corp
Current assignee: Aearo Technologies LLC
Priority date: 1974-11-29
Filing date: 1974-11-29
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04

Abstract

A lens surfacing machine having a rotatable lower tool supporting spindle and an oscillational work actuating head of minimal mass and weight. Vibration dampeners reducing noise, wear and lens breakage are incorporated in the tool and work actuating components of the machine. A motor driven compound motion imparting system, protected from abrasive contamination, produces oscillation of the work actuating head with a continuous break up of the oscillatory motion and simultaneous rotation of the tool supporting spindle.

Description

[ Nov. 4, 1975 3,093,939 6/1963 Dalton............................... 51/124 L 3,383,806 5/1968 Stratemeyer................. 51/134.5

Primary Examiner--Othe1l M. Simpson Attorney, Agent, or FirmH. R. Berkenstock, Jr.; William C. Nealon [57] ABSTRACT A lens surfacing machine having a rotatable lower tool supporting spindle and an oscillational work actuating head of minimal mass and weight. Vibration dampeners reducing noise, wear and lens breakage are incorporated in the tool and work actuating components of the machine. A motor driven compound motion imparting system, protected from abrasive contamination, produces oscillation of the work actuating head with a continuous break up of the oscillatory motion and simultaneous rotation of the tool supporting spin- 10 Claims, 7 Drawing Figures Umted States Patent [191 Prunier Louis Prunier, Oxford, Mass.

Southbridge, Mass.

Nov. 29, 1974 US. 51/124 L B24B 7/00; B24B 9/00 Field of 51/105 LG, 124 L, 134.5

References Cited UNITED STATES PATENTS LENS SURFACING APPARATUS [75] Inventor:

[73] Assignee: American Optical Corporation,

[22] Filed:

[21] Appl. No: 528,298

[51] Int.

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LLLLL 1 mmmmm u 55555 i a nnmeny M & wmmkd 1 i.

Pne ii.

mw mm SBSDK US. Patent N0v.4,1975 simetlom 3,916,574

FIG. I

U.S.. Patent Nov. 4, 1975 Sheet 2 of4 3,916,574

US Patent Nov. 4, 1975 Sheet 3 of4 3,916,574

LENS SURFACING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to apparatus for surfacing articles such as lenses and has particular reference to improvements in high speed lens grinding and polishing machinery.

2. Discussion of the Prior Art In the manufacture of ophthalmic lenses, preliminary operations of milling or generating the lenses to their desired surface configurations are usually followed by fine grinding, commonly referred to as fining, and polishing.

Fining operations are conducted to true the curvatures of milled or generated surfaces and prepare such surfaces for polishing by removing excessive roughness, surface cracks and other such irregularities.

Polishing is then undertaken and continued for a period of time sufficient to produce a surface of optical quality. Those interested in a detailed technical description of the requirements for optical quality may refer to Optical Glass Working by F. Twyman published by Hilger & Watts Ltd. of London, 1955, pages 154 et seq.

In general, the time required to fine and/or polish a lens is dependent upon the amount and kind of relative motion which can be produced between the lens and tool and the rate at which the motion is imparted. That is, with factors such as texture of the initially milled or generated surface, the smoothness desired of the fined surface, pressure applied to the workpiece in fining and/or polishing and characteristics of the polishing medium all being equal, greater amounts of relative motion and faster operating speeds will reduce fining and/or polishing time.

Heretofore, however, attempts to reduce fining and polishing times with increased motion and operating speeds have been met with such adverse effects as machinery breakdown and/or excessive wear resulting from vibration, lens breakage or inferior surface finishes and undue noise pollution.

The present invention accomplishes a substantial reduction of prior art fining and polishing times and a lessening of product scrap yield by overcoming previous vibration problems and limitations of the extent and directions of relative tool and workpiece motion.

Accordingly, a principal object of the invention is to provide for improved and more efficient operation of lens surfacing apparatuses, lower product scrap yield and higher quality output with longer than usual machinery lifetime and a substantial reduction in occurrences of breakdown, a shortening of repair and maintenance times and large reduction of machinery noise pollution.

SUMMARY OF THE INVENTION The invention relates to improvements in a type of lens surfacing machine having a rotatable lower tool supporting spindle and an oscillational work actuating head.

The present work actuating head is free of the usual individually power driven spindle apparatuses and, accordingly, is of minimal mass and weight thereby greatly reducing machine vibration and its adverse affects. Vibration dampeners further reducing noise, wear and lens breakage are incorporated in both the 2 tool and work actuating components of the present machine.

A motor driven motion imparting system protected from contamination by abrasive slurry is constructed and arranged to produce a compound oscillatory motion of the work actuating head. This compound motion uniquely obviates the need for conventional ungainly and heavy spindle rotating devices heretofor used in surfacing machine heads.

With the foregoing improvements minimizing vibration problems, noise pollution, lens breakage and machinery wear, maintenance problems are still further lessened and machine lifetime is extended by a unique sealing of critical machinery bearing components and other such moving parts from abrasive slurry contamination. Additionally, an abrasive slurry overflow system is providedas a safeguard against possible malfunction of the sealing means to assure against contamination of the machine bearings.

Details of the invention will become more readily apparent from the following description when taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration, in perspective, of a preferred embodiment of the invention;

FIG. 2 is a fragmentary partially cross-sectioned elevational view of a lens surfacing unit of the embodiment of the invention shown in FIG. 1;

FIG. 3 is a fragmentary rear view, in perspective, of the upper portion of the unit shown in FIG. 2;

FIG. 4 is a vertical cross section of the uppermost portion of the surfacing unit shown in FIG. 2;

FIG. 5 is a cross sectional view taken generally along line 55 of FIG. 4;

FIG. 6 is a view similar to that of FIG. 5 but illustrating a modification of the apparatus shown in FIG. 5; and

FIG. 7 is a cross-sectional view of a portion of the apparatus shown in FIG. 3, the cross-section being taken from line 77 looking in the direction of its arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to the drawings, the lens surfacing machine 10 (FIG. 1) of the invention preferably comprises a pair of identical

lens surfacing units

12 and 14 within a single shroud 16. Shroud 16 has an opening 18 through which lenses may be positioned in and unloaded from

surfacing units

12 and 14; Cover 20 is adapted to be selectively placed over opening 18 to prevent excessive outward splashing of abrasive slurry during lens grinding or polishing operations performed with

units

12 and 14.

Only one of

units

12 and 14, namely unit 12, is illustrated in FIGS. 2-7 of the drawings and will be described in detail hereinafter; it being understood that unit 14 is substantially identical. It is further pointed out that machine shroud 16 may be readily adapted, within the scope of the present invention, to incorporate more than the illustrated two surfacing units or, alternatively, only a single unit such as will be described in detail hereinafter.

Surfacing unit 12 (FIGS. 2, 3 and 4) comprises oscillational work actuating head 22 and rotatable tool supporting spindle structure 24. Spindle structure 24 comprises rotatable, vertically disposed spindle 26 journaled in housing 28 which is fixedly supported upon 3 machine base 30 within shroud 16. Spindle 26 is topped with tool holder 32 and a depending generally hollow umbrella-shaped support 34 for lens supporting and axis aligning harness mechanism 36.

Tool holder 32, support 34 and harness mechanism 36 rotate in unison with spindle 26 to impart rotation to surfacing tool 38.

Surfacing tool 38, which may be of any one of various types commonly used in the industry, is preferably provided with a wire mesh pad 40, e.g. of the'type shown and described in US. Pat. No. 2,886,923, when a lens surface grinding operation is to be performed with ma- Q chine 10. Alternatively, the tool 38, or a similar tool, is

provided with a polishing pad of plastic, felt or other material conventionally used, as shown in FIGS. 4 and 5, for example.

It is to be understood that this showing of both wire mesh grinding pads 40 and polishing pads 42 in different views of the same embodiment of the invention (unit 12), has been used to minimize drawing detail and to emphasize the adaptability of unit 12 to either a surface grinding or a surface polishing operation. It is to be further understood that surface grinding and surface polishing operations are usually performed in separate but identical machines to prevent contamination of polishing slurries with grinding abrasives and vice versa. In a grinding operation, a slurry of emery particles supplied through a nozzle 44 would ordinarily be used while the same or a similar nozzle would supply a slurry of a polishing medium such as zirconium oxide or cerium oxide in water during the course of a polishing operation.

Those interested in greater details of lens surface grinding and surface polishing operations in general, may refer to US. Pat. Nos. 3,093,939 and 2,916,857.

Rotation of spindle 26 and tool 38 is produced by belt drive mechanism 46 (FIG. 2) powered by motor 48. Workpiece holder (e.g. lens block 50, FIGS. 4 and carrying a lens 52 in conventional fashion for surfacing, is secured in harness 36 by locating pins 54 (FIG. 5) in yoke 56. Yoke 56 having its two opposite ends 58 pivotally mounted to harness 36 (FIG. 2) prevents independent rotation of lens block 50 and lens 52 relative to tool 38.

Flat spring coil 60 (FIG. 2) of axis aligning harness 36 is secured to support 34, e.g. by stud 62 so as to prevent the aforesaid relative rotational movement between lens 52 and tool 38 while freely permitting oscillational movement of harness 36 and lens 52 continuously during simultaneous rotation of the entire unit of spindle 26, tool holder 32, tool 38, harness 36, lens block 50 and lens 52.

With such as the aforesaid rotational and oscillational action, lens 52 is adapted to be surfaced whether surfacing is desired to produce a toric negative (concave) curvature thereon or a simple spherical negative curvature. The term surfacing as used herein is intended to include both surface grinding and surface polishing operations.

More specific details of the function of axis aligning harnesses such as 36 and modifications thereof may be had by reference to US Pat. No. 3,093,939. Another useful form of axis aligning harness is shown and described in US. Pat. No. 2,916,857.

While the aforesaid description of lens surfacing operations has thus far made reference only to the production of negative toric or spherical surfaces as illustrated in FIGS. 4 and 5, simple substitution of a tool 64 having a concave working surface 66 (FIG. 6) covered either with a wire mesh pad 40, as shown, or with a polishing pad 42, will provide the means necessary for sur-- facing positive (convex) surfaces 68 upon a lens 52, for example. This convex surface 68 and working surface 66 may selectively be either spherically or torically curved as determined by the selection of tool 64, i.e. whether tool 64 has a toric or spherical working surface 66.

In order to produce the aforesaid oscillational movement of

lens

52 or 52 over tool 38 or tool 64, head 22 of surfacing unit 12 (FIGS. 2 and 4) is provided with drive pin 70 (FIGS. 4, 5 and 6) which is stationary in head 22 and normally relatively permanently but removably seated in yoke 56.

A rearward extension 72 of head 22 pivotally mounted on horizontal shaft 74 provides means for selectively moving head 22 downwardly toward and upwardly away from tool 38 for selective placement and removal of blocked lenses 52, with their blocks 50, from surfacing unit 12. An air cylinder 73 or other suitable actuating means connected to lever 75 may be used to raise and lower head 22. The lifting of yoke 56 upwardly to release pins 54 from block 50 is effected by washer 76 which is fastened to head 22. Washer 76 is adapted to engage lip 78 of retainer 80 when head 22 is raised. Head 22 may be disconnected from harness 56 by removal of retainer 80.

It can be seen from the drawings that the head 22 of surfacing unit 12 is entirely free of the usual separately motor driven eccentric pin rotating mechanism. Reasons for the present invention making it possible to eliminate such prior art complex ungainly and weighty mechanisms will become more readily apparent from a description of the oscillation producing mechanism of the present apparatus which will follow shortly.

In the meantime, with continued reference to details of head 22, it will be seen by reference to FIG. 4 that prior art problems of machine vibration which are at least partly overcome by the aforementioned simplification of head 22 design, are still further reduced, if not eliminated, by resiliently mounting the drive pin 70 and supporting rod 82 in head 22. This is accomplished by the incorporation of relatively hard but resilient rubber bushings 84 vulcanized to supporting

sleeves

86 and 88 of metal. Rubber bushings 84, acting as vibration dampening means, absorb both high and low frequency vibrations whether produced by movement of lens 52 over the abrading surface of tool 38 and/or from other movable parts of unit 12.

In conjunction with the dampening means 84, a hard rubber or plastic ring 90 in tool holder 32 (FIG. 4) upon which tool 38 is seated further functions to absorb machine induced vibration and/or minimize parts chatter. Resilient ring 90 (FIGS. 4 and 5) is formed with diametrically opposed enlarged key-shaped portions 92 (FIG. 4) over which slot 94 in tool 38 is adapted to fit and thus key the tool 38 against independent rotation on holder 32. Tool 38 may be readily, simply lifted from tool 32 for removal and similarly readily replaced by being dropped onto ring 90.

A compound oscillational movement of head 22 which, as mentioned hereinabove, obviates the hitherto need for complex, heavy and ungainly head mechanisms, is produced by drive unit 96. Unit 96 is powered by motor 48 through belt and pulley mechanism 98 (FIGS. 2 and 3).

Referring more particularlyto FIGS. ,3 and 7, the aforementioned rearward extension 72 of head 22 which is permitted to pivot onshaft 74' is fixed against lateral movement therealong by anchor sleeves 100. Opposite ends of shaft 74 are secured in

rockers

102 and 102a which, in turn, are pivoted upon rods 104 bracketed to base 30 of machine 10.

Rocker 102 is provided with arm 106 which is actuated by drive unit 96 through connecting rod 108. End 110 of connecting rod 108 is driven with a compound eccentric motion which is duplicated at end 112 and transmitted to rocker arm 106. This compound eccentric motion being imparted to rocker 102 and shaft 74 produces the compound oscillational motion (oscillation with break up) of head 22.

Referring more particularly to FIG. 7, details of the mechanism (drive unit 96) involved in producing the aforesaid compound motion are as follows:

Drive unit 96 comprises cylindrical housing 114 within which hollow drive shaft 116 is concentrically journaled by bearings 118. Belt and pulley drive mechanism 98 is affixed to shaft 116. Hollow shaft 116 has channel 120 extending therethrough within which second drive shaft 122 is journaled by bearings 124. Opposite ends of the second drive shaft 122 extend outwardly of channel 120.

Adjacent one end 126 of drive unit 96, spur gear 128 is affixed to drive shaft 122 in mesh with teeth of internal gear 130. Gear 130 is bolted or otherwise fastened to housing 1 14 of unit 96.

Fixed to the opposite end of shaft 122, e.g. end 132, is eccentric 134 to which end 110 of connecting rod 108 is journaled by bearings 136. Bearings 136 are preferably of a Well-known commercially available variety which, with secureness and intimacy of fit upon eccentric 134, provide connecting rod 108 with freedom of limited lateral movement without chatter or looseness of fit. By the use of such bearing means, reasonable machining tolerances may be permitted in the manufacture of parts of drive unit 96 and/or rocker 102 without fear of binding or undue frictional problems occurring in the operation of the unit. End 112 of connecting rod 108 is similarly journaled to rocker arm 106.

The operation of drive unit 96 is as follows:

Belt and pulley drive 98, when set into motion by motor 48, rotates main drive shaft 116 causing shaft 122 to revolve with it, but eccentrically. While so re volving eccentrically, second drive shaft 122 is simultaneously rotated by gear 128. Gear 128 having fewer teeth than gear 130 transverses the inner periphery of gear 130. This rotation of shaft 122, while itself being eccentrically revolved, produces a second off-center motion of eccentric 134. The first revolving motion of hollow main drive shaft 116 thus produces a back and forth relatively slow cranking action upon connecting rod 108 which continually, during this cranking action, is reciprocated back and forth over a short distance several times per each larger cranking operation. The resulting compound cranking motion of connecting rod 108 is, accordingly, transmitted to rocker arm 106, rocker 102, shaft 74 and head 22 which convert the cranking motion to a compound oscillational movement causing drive pin 70 to move a lens 52 being abraded accordingly. This compound oscillatory (break up) movement is generally of the type schematically illustrated by line 138 (FIG. 4). It takes place in both directions of oscillation of lens 52 across tool 38 continuously during simultaneous rotation of the whole unit within and including harness 36 and yoke 56.

Referring now more particularly to the arrangement of the hollow umbrella shaped support 34 for harness 36 which rotates harness 36, the present invention features the provision of a novel resilient seal 140 (FIG. 2) preventing contamination of bearings 142 and/or other internal components of the tool drive mechanism of unit 12.

Grinding or polishing slurry emitted from nozzle 44 and flowing downwardly over a lens being surfaced and thence over the umbrella-shaped support 34 into splash pan l43 for return to its pumping station is deflected away from sea] 140 by flange 144 of support 34. A typical slurry pumping and delivery system is shown in US. Pat. No. 3,093,939 and, accordingly, needs no further description herein.

While flange 144 deflects most of the grinding or polishing slurry away from'seal 140, that not being so deflected is prevented from reaching internal parts of the spindle rotating mechanism by seal 140. Seal 140 is frictionally fitted to annular support 146 which is stationary upon machine base 30.

As a safeguard against failure of seal 140 to prevent abrasive slurry from passing thereover, e.g. due to flooding in pan 143, opening 148 provides an emergency draininto lower portions of machine 10 where no harm can come therefrom.

I claim:

1. In lens surfacing apparatus including a rotatable tool supporting structure, means for rotating said structure, work harnessing means rotatable with said tool supporting structure and a workpiece actuating head having a drive pin, the improvement comprising:

means for fixedly mounting said drive pin in said head;

a tool holder in said tool supporting structure;

a drive unit remote from said head for producing a compound cranking motion and means for actuating said unit;

rocker means interconnecting said drive unit and head for effecting conversion of said compound cranking motion into a compound oscillational motion and for oscillating said head accordingly when said drive unit is actuated; whereby rotation of said tool supporting structure and work harness with simultaneous actuation of said drive unit produces a surfacing motion between a workpiece in said harnessing means and a tool on said tool supporting structure which surfacing motion includes oscillation of said workpiece over said tool with a continuous breakup of its oscillational movement.

2. Apparatus according to claim 1 wherein said means for fixedly mounting said drive pin in said head includes a rod to one end of which said drive pin is immovably attached, said rod extending through and depending from a forward portion of said head; and

an immovable but vibration dampening bushing surrounding at least a substantial portion of said rod in said head.

3. The lens surfacing apparatus according to claim 2 wherein said bushing is externally and internally surrounded by metallic sleeves and the material of said bushing is attached to said sleeves.

4. The apparatus according to claim 3 wherein said bushing is formed of hard rubber and is vulcanized to said sleeves.

5. The apparatus according to claim 1 wherein said tool holder includes an annular tool receiving seat formed of resilient material.

6. Lens surfacing apparatus according to claim 1 wherein said drive unit comprises a main housing, a hollow shaft journaled to rotate concentrically within said housing, means for rotating said hollow shaft, said shaft having an eccentrically disposed opening extending longitudinally therethrough, a second shaft journaled in said eccentric opening of said hollow shaft, opposite ends of said second shaft extending outwardly of said hollow shaft, one of said ends of said second shaft having an eccentric crank and one end of a connecting rod journaled thereon, the opposite end of said second shaft having a drive gear fixed thereto and an internal gear in mesh with said drive gear and said internal gear being fixed to said housing.

7. Lens surfacing apparatus according to claim 6 wherein said rocker means of claim 1 includes an actuating arm to which the opposite terminal end of said connecting rod is journaled and a shaft carrying said 8 workpiece actuating head wherewith operation of said drive unit effects said conversion of said compound cranking motion into said compound oscillational motion.

8. Lens surfacing apparatus according to claim 1 wherein said means for rotating said tool supporting structure and for actuating said drive unit comprises a single motor.

9. Lens surfacing apparatus according to claim 1 wherein said rotatable tool supporting structure includes internal journaling and said apparatus further includes a stationary annular seal for protecting said journaling from external contaminants, said seal normally abutting said rotatable structure with minimal frictional force thereagainst.

10. Lens surfacing apparatus according to claim 9 further including a stationary annular support for said seal, said seal being adjustable longitudinally along said support and frictionally self-held in preselected positions of adjustment therealong.

Claims

1. In lens surfacing apparatus including a rotatable tool supporting structure, means for rotating said structure, work harnessing means rotatable with said tool supporting structure and a workpiece actuating head having a drive pin, the improvement comprising: means for fixedly mounting said drive pin in said head; a tool holder in said tool supporting structure; a drive unit remote from said head for producing a compound cranking motion and means for actuating said unit; rocker means interconnecting said drive unit and head for effecting conversion of said compound cranking motion into a compound oscillational motion and for oscillAting said head accordingly when said drive unit is actuated; whereby rotation of said tool supporting structure and work harness with simultaneous actuation of said drive unit produces a surfacing motion between a workpiece in said harnessing means and a tool on said tool supporting structure which surfacing motion includes oscillation of said workpiece over said tool with a continuous breakup of its oscillational movement.

2. Apparatus according to claim 1 wherein said means for fixedly mounting said drive pin in said head includes a rod to one end of which said drive pin is immovably attached, said rod extending through and depending from a forward portion of said head; and an immovable but vibration dampening bushing surrounding at least a substantial portion of said rod in said head.

7. Lens surfacing apparatus according to claim 6 wherein said rocker means of claim 1 includes an actuating arm to which the opposite terminal end of said connecting rod is journaled and a shaft carrying said workpiece actuating head wherewith operation of said drive unit effects said conversion of said compound cranking motion into said compound oscillational motion.