US2458384A - Grinding of lenses or of dies therefor - Google Patents

Grinding of lenses or of dies therefor Download PDF

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Publication number
US2458384A
US2458384A US581730A US58173045A US2458384A US 2458384 A US2458384 A US 2458384A US 581730 A US581730 A US 581730A US 58173045 A US58173045 A US 58173045A US 2458384 A US2458384 A US 2458384A
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United States
Prior art keywords
tool
workpiece
edge
grinding
axis
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Expired - Lifetime
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US581730A
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English (en)
Inventor
Jeffree John Henry
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Combined Optical Industries Ltd
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Combined Optical Industries Ltd
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Publication date
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B13/00—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor
    • B24B13/02—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor by means of tools with abrading surfaces corresponding in shape with the lenses to be made
    • B24B13/026—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor by means of tools with abrading surfaces corresponding in shape with the lenses to be made the contact between tool and workpiece being a line
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B9/00—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor
    • B24B9/02—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground
    • B24B9/06—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain
    • B24B9/08—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain of glass
    • B24B9/14—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain of glass of optical work, e.g. lenses, prisms

Definitions

  • This invention relates to improved methods an apparatus for grinding and/or polishing curved surfaces of various kinds including aspheric surfaces, particularly lenses and the dies used for the moulding of lenses from transparent plastics, as described for example in Springfield United States Patent No, 2,314,838, dated March 23, 1943.
  • the word lens in this specification is to be understood to include a mirror, where the context cal surfaces, and the grinding of lenses which give cylindrical and spherical corrections are well known. While, however, various kinds of optical systems are susceptible of improvement by the inclusion therein of aspheric lens or mirror surfaces, the production of such surfaces of suflicient precision by known methods is so difficult that little use of the same in optical systems has been made hitherto.
  • the objects of this invention comprise the provision of methods and apparatus whereby aspheric as well as spherical surfaces can be ground and polished effectively and with considerable precision.
  • the term aspheric as used herein should be understood to include surfaces of revolutions such as paraboloids, ellipsoid-s and hyperboloids(generally though not exclusive 1y prolate in form) and also to include surfaces having curvatures of third order or of higher orders, which are symmetrically curved relative to an axis, including surfaces which are concave at the middle and convex near the periphery or vice versa.
  • the present invention can beutilized in all such cases, its simplest application however being to the grinding and polishing of prolate surfaces of revolution which can be rotated on their axes of-symmetry during the process.
  • the workpiece is first roughly formedto the desired surface (such for example as one of the surfaces of revolution), and this is rotated about its axis of symmetry.
  • This surface is scraped (9r, when the polishing stage is reached. it may be polished), by the edge of a lapping tool similar to a profile cutter which is initially shaped roughly to fit the surface.
  • This tool is held under sumcient pressure against the surface acted upon sufllcient movement in its own axial direction, 1. e.. in the direction of the axis of the curve imparted to the tool edge by grinding, to maintain contact between the edge and the surface.
  • the axis about which thetool is caused to swing will not pass through a focus of the curved surface, but will be otherwise determined, as is later explained.
  • an abrasivelubricant composition such as a suspension of finely divided mineral matter in a viscous liquid such as oil or glycerine is preferably-used on the workpiece, and both the surface of the workpiece and the edge of the tool are abraded thereby to attain their final shape appropriate to their initial shape and the relative movements of workpiece and tool.
  • features of the improved method will, preferably, include the variation of the traverse of the tool edge across the workpiece, i. e. the continual displacement of the end positions of the 'tool edge, back and forth, during its reciprocawhile it is reciprocated back and forth across the causing thetool to swing about a focus (the more distant one) of the surface, while permitting it tion, to prevent the possibility of slight ridges being formed on the work, as might happen at the limits of movement of the edge if it always changed its direction from forward to back or vice versa at the same points; and also the carrying out of the desired movement ,of the tool, in such manner as to cause its edge continually to sweep the abrasive lubricant towards the centre of the workpiece.
  • This can be done, in suitable cases, by causing the traverse of the tool to be slightly off centre. that is, by horizontal adjustment of the tool in its own plane.
  • Figure 2 is a front elevation thereof, shown partly in section,
  • Figure 3 is a partial vertical section on line 3-3 of Figure 1, on an enlarged scale,
  • Figure 4 is a partial section along the plane of line IV-IV of Figure 2;
  • Figure 5 is a partial elevation looking from the left in Figure 2;
  • Figure '6 indicates diagrammatically the mounting of the workpiece for grinding a, hyperboloid (concave) surface
  • Figure 7 indicates diagrammatically the mounting of the workpiece for grinding a concave ellipsoid (prolate) surface
  • Figure 8 indicates diagrammatically the mounting of theworkpiece for grinding a concave ellipsoid (oblate) surface
  • Figure 9 indicates diagrammatically the mounting of the workpiece for grinding a, prolate convex hyperbolic surface
  • Figure 10 indicates diagrammatically the mounting of the workpiece for grinding a prolate convex ellipsoid surface
  • Figure 11 indicates diagrammatically the mounting of the workpiece for grinding an oblate convex ellipsoid surface.
  • substantially upright frame members l3 are pivoted at their lower ends on rod I2 mounted on block II, which is secured on the fixed horizontal table I0.
  • Members I3 carry a transverse pivot rod I4 at their upper ends, on which are pivoted two substantially horizontal frame members I5, these arms I5 being held against this pivot rod, in the formof construction illustrated, by leaf springs I5a.
  • Members I5 carry at their opposite ends a transverse pivot rod I6 on which are pivoted arms H which have, integral therewith or rigidly secured thereto, a tool-supporting transverse member Ho.
  • the tool I8 is secured to member Ila, the tool being, in the form of construction illustrated, a flat metal sheet, the lower edge of which is shaped roughly to fit the curved surface which is to be ground, different tools being provided for the various surfaces such as hyperboloids, ellipsoids, etc., which are to be ground.
  • the tool may be secured to member I la by means of a screw I8a. passing through a vertical slot I8b in the tool, and thence into member He the slot being wider than the shank of the screw, to permit some horizontal adjustment of the tool in its own plane (for a purpose hereafter explained), before tightening the screw, the head of which I8c is wide enough to have a firm bearing on the tool on both sides of the slot.
  • the lower edge of the tool rests on the preformed surface of the workpiece I9, mounted on a workpiece holder which is rotated about its vertical axis by driving pulley 20L
  • the workpiece may be, for example, a steel die which is to be ground and polished to a desired curved surface for use in the moulding of optical lenses from plastics, the curved surface shown in the drawings being ellipsoidal.
  • I is secured to this standard at a desired level above (or below) table II! by means indicated as the screw 2I Ia, the transverse flange of the standard being, conveniently, provided with a vertical slot, or suitably spaced openings, for this purpose.
  • This bracket carries a bolt 2 I2 extending transversely beyond its inner surface, and may be slidably engaged, on one of its lateral surfaces, by a vertical bar 22 having perforations 22a extending therethrough at various points.
  • the edge of this bar is insllding contact with bolt 2I2, fitting in a slotted guide 4 2I2a. thereon, with which it is held resiliently in contact, as by means of spring 222, which may be removably extended from bar 22 to a pin 2IIb on bracket 2.
  • the pivot rod I6 is extended into one of the perforations 22a of bar 22, so that the arms I5 are approximately horizontal when the lower edge of the tool is resting on the workpiece I9.
  • the tool I8 is rigidly secured to bar 22 to move therewith, as by securing one of the arms I! to the bar 22 by a pin extended into another one of the perforations 22a of the bar.
  • the tool and the work are mutuallyabraded until, from an original rough form, they reach forms that fit each other at all positions of the working stroke. Since their angular relation to each other varies over the stroke, according to a predetermined law, the curve they acquire is determined by the law of this variation, as well as by the rough curve from which they started.
  • the case is analogous to that of ordinary grinding of spheres together, where the curvature reached depends partly on the initial rough forms of tool and work, but the kind of curve (sphere) is that whereby the tool and work can fit each other in any position. In my machine, however, it is a surface and an edge that must fit, instead of two surfaces, and the conditions under which they fit are restricted by the position of the pivot controlling the angular position of the tool.
  • the apparatus as shown is arranged for the grinding of a prolate surface of revolution, specifically an ellipsoidal surface.
  • a prolate surface of revolution specifically an ellipsoidal surface.
  • the pivot 2I2 must therefore be positioned approximately at such point.
  • the pivot 2I2 must be positioned at other points than that shown, to lie approximately at a focus of the desired curvature, and for other types of curvature other adjustments must be made, as will be discussed hereafter.
  • a vertical spindle IIlI at the right hand end of table I0 is rotated from motor 35 by worm and wormwheel 34, 31 and belt 38, which passes over the encased.
  • the workholder 20 is rotated by another belt which passes around vertical axis extending upwardly from carrier 23,
  • Disc 21 is provided with a diametrically-extending slot 42 in which is mounted a screw 44 on which a slider 43 is adjustably mounted.
  • This slider carries a driving pin 45 on which slotted bar 28 is mounted, this bar being secured in adjusted position by two locking washers 46 on pin 45.
  • the traverse of the tool 18 is effected through stirrup 30 secured to template carrier Ila, universal joint 3
  • the throw of the eccentric or crankpin '2 determines the length of stroke. of the working edge of the template back and forth over the workpiece, this length varying as crank-pin 24
  • the rotation of pin 45 about its centre causes the whole stroke to be displaced in the lengthwise direction of the stroke, so that its extreme positions at both ends will continuously vary, a series of such variations being completed each revolution of the disc 21.
  • the adjust-- frame l3, i5, i1, connected to the tool is to pre--.
  • the hinged frame permits vertical movement thereof, in accordance with the curved contour of the surface tr aversed by'the edge. It also, of course, permits movement of the tool normal ornearly normal to its own plane, which constitutes its working stroke.
  • a third possible movement of translation a horizontal movement of the tool in its own plane, is prevented by the construction as shown, during operation.
  • the tool may be shifted horizontally in its own plane, by suitably adjusting the position of screw 18a in slot i8b of the tool, as described above in connection with Figure 3, so that the tool may be maintained somewhat off centre in this plane, to enable it to sweep the abrasive-lubricant continuously towards the centre of the workpiece.
  • edge portions of the curved work surface in cases in which such edge portions differ markedly from the curvature of the remainder of the surface.
  • the utility of this expedient in particular cases can be determined readily by test.
  • the inclination of the tool will not vary symmetrically with respect to the axis of the workpiece as described above.
  • the template in its mid position will be inclined, to the vertical, and may remain so throughout its traverse.
  • the position of the pivot will be found to lie on the periphery of a circle tangent to the central portion of the curvature to be traced, which circle has a radius equal to one half the radius of the central portion of the oblate surface. Considerations indicating the position of the pivotal point upon such periphery need not be iven here.
  • the correct position will be found to be the one which, when used as a pivot as described, will cause the tool edge always to maintain contact (at least as to its central portion), with the surface to be'ground, and this point can always be found, either by theoretical considerations checked up by trial, or by trial and error, or empirical, methods, until the correct position is ascertained.
  • I, shown in the drawings, but carrying a pivot pin similar to the pin 212 at the required distance from the axis of the workpiece will be provided.
  • astigmatic surfaces having different curvatures in different directions may, if symmetrically curved relative to an axis, be worked while rotating the workpiece on this axis, by making the inclination of the tool depend on the angle of rotation of the workpiece as well as on the extent of traverse of the tool.
  • the principle holds good that a point must be found through which the pivot 2 I2 is extended, about which the bar 22 will swing, this being so located that the tool edge will always incline at such angles to the surface of the workpiece as to continue to fit the same when the desired final shape of the surface is attained.
  • abrasive-lubricant composition In the case where an aspheric surface of great precision is imparted to a steel die the abrasive-lubricant composition may be changed during the grinding operation.
  • a suspension of carborundum in oil may first be used, then a suspension of finely divided alumina in oil or glycerine and finally a suspension of r diamantine in oil or glycerine. Polishing may be effected in the same machine, the tool in that case having a flexible edge or an edge of leather or soft fabric.
  • a workpiece holder means for rotating it about an axis of symmetry of a workpiece thereon, a pivot member, a tool carrier, means for supporting said carrier in sliding engagement with said pivot member, to swing thereabout, with the edge of a tool carried thereby pressed against the surface of a workpiece on said workholder, and means for swinging said edge across said surface with a varied stroke
  • a rotatable eccentric pin a carrier pivoted thereto, a disc journalled on said carrier and rotated by driving connection from said pin, a pin eccentrically mounted on said disc, and driving connections between said last named pin and said tool carrier.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
US581730A 1943-10-26 1945-03-09 Grinding of lenses or of dies therefor Expired - Lifetime US2458384A (en)

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GB2458384X 1943-10-26

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BE (1) BE459223A (enrdf_load_stackoverflow)
CH (1) CH265596A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2709873A (en) * 1953-08-20 1955-06-07 Robert E Lewis Machine for grinding paraboloidal surfaces
US3494077A (en) * 1967-06-23 1970-02-10 Rogers & Clarke Mfg Co Machine tool having a variable-stroke drive
CN112793062A (zh) * 2021-02-04 2021-05-14 四川恒格光电科技有限公司 一种闪光灯透镜飞边去除装置

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US761207A (en) * 1904-02-17 1904-05-31 Frank M Clark Machine for grinding lenses.
US857791A (en) * 1906-03-19 1907-06-25 Charles H Philbrick Machine for grinding lenses.
US947774A (en) * 1907-03-08 1910-01-25 Jules Alphonse Gustave Rousset Lens-shaping machine.
US995393A (en) * 1909-12-27 1911-06-13 Samuel Witmer Machine for grinding variable curves.
US1221280A (en) * 1915-11-16 1917-04-03 John Brockbank Apparatus for grinding lenses.
US1343522A (en) * 1916-04-15 1920-06-15 Universal Grinding Machine Com Process for grinding and polishing lenses
US1383863A (en) * 1914-03-18 1921-07-05 Marie E Scheuerle Method of making bifocal lenses
US1520703A (en) * 1924-08-23 1924-12-30 Pittsburgh Plate Glass Co Machine for smoothing curved surfaces
US1639012A (en) * 1924-12-03 1927-08-16 American Optical Corp Surfacing machine
US1827748A (en) * 1927-08-18 1931-10-20 Arthur J Holman Apparatus for grinding and polishing spherical lenses
FR755354A (fr) * 1933-05-10 1933-11-23 Machine pour la rectification de surfaces sphériques ou non sphériques
US2176154A (en) * 1936-12-01 1939-10-17 Shannon Joseph Lens grinding machine
US2352386A (en) * 1942-06-29 1944-06-27 Bausch & Lomb Optical flat generator

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US761207A (en) * 1904-02-17 1904-05-31 Frank M Clark Machine for grinding lenses.
US857791A (en) * 1906-03-19 1907-06-25 Charles H Philbrick Machine for grinding lenses.
US947774A (en) * 1907-03-08 1910-01-25 Jules Alphonse Gustave Rousset Lens-shaping machine.
US995393A (en) * 1909-12-27 1911-06-13 Samuel Witmer Machine for grinding variable curves.
US1383863A (en) * 1914-03-18 1921-07-05 Marie E Scheuerle Method of making bifocal lenses
US1221280A (en) * 1915-11-16 1917-04-03 John Brockbank Apparatus for grinding lenses.
US1343522A (en) * 1916-04-15 1920-06-15 Universal Grinding Machine Com Process for grinding and polishing lenses
US1520703A (en) * 1924-08-23 1924-12-30 Pittsburgh Plate Glass Co Machine for smoothing curved surfaces
US1639012A (en) * 1924-12-03 1927-08-16 American Optical Corp Surfacing machine
US1827748A (en) * 1927-08-18 1931-10-20 Arthur J Holman Apparatus for grinding and polishing spherical lenses
FR755354A (fr) * 1933-05-10 1933-11-23 Machine pour la rectification de surfaces sphériques ou non sphériques
US2176154A (en) * 1936-12-01 1939-10-17 Shannon Joseph Lens grinding machine
US2352386A (en) * 1942-06-29 1944-06-27 Bausch & Lomb Optical flat generator

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2709873A (en) * 1953-08-20 1955-06-07 Robert E Lewis Machine for grinding paraboloidal surfaces
US3494077A (en) * 1967-06-23 1970-02-10 Rogers & Clarke Mfg Co Machine tool having a variable-stroke drive
CN112793062A (zh) * 2021-02-04 2021-05-14 四川恒格光电科技有限公司 一种闪光灯透镜飞边去除装置
CN112793062B (zh) * 2021-02-04 2022-08-05 东莞市恒格光电科技有限公司 一种闪光灯透镜飞边去除装置

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Publication number Publication date
CH265596A (fr) 1949-12-15
BE459223A (enrdf_load_stackoverflow) 1945-08-31

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