US2435126A - Formation of curved surfaces of prescribed figure by grinding and/or polishing - Google Patents

Formation of curved surfaces of prescribed figure by grinding and/or polishing Download PDF

Info

Publication number
US2435126A
US2435126A US668124A US66812446A US2435126A US 2435126 A US2435126 A US 2435126A US 668124 A US668124 A US 668124A US 66812446 A US66812446 A US 66812446A US 2435126 A US2435126 A US 2435126A
Authority
US
United States
Prior art keywords
grinding
polishing
pad
prescribed
bar
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US668124A
Other languages
English (en)
Inventor
Burch Cecil Reginald
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Metropolitan Vickers Electrical Co Ltd
Original Assignee
Metropolitan Vickers Electrical Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Metropolitan Vickers Electrical Co Ltd filed Critical Metropolitan Vickers Electrical Co Ltd
Application granted granted Critical
Publication of US2435126A publication Critical patent/US2435126A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • B24B13/06—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor grinding of lenses, the tool or work being controlled by information-carrying means, e.g. patterns, punched tapes, magnetic tapes
    • B24B13/065—Machines or devices designed for grinding or polishing optical surfaces on lenses or surfaces of similar shape on other work; Accessories therefor grinding of lenses, the tool or work being controlled by information-carrying means, e.g. patterns, punched tapes, magnetic tapes using a template
    • 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
    • B24B17/00—Special adaptations of machines or devices for grinding controlled by patterns, drawings, magnetic tapes or the like; Accessories therefor

Definitions

  • This invention relates to the formation, by grinding and/or polishing, of curved surfaces of prescribed figure of revolution, although notably applicable in the manufacture of aspheric lenses and mirrors composed of plastic or other glass, the invention is capable of wider application.
  • the present invention has for an object to enable the prescribed shape to be approached to any desired degree with the exercise of relatively little intelligent supervision and personal skill and without involving positive generation of the desired shape, with its attendant disadvantages and limitations especially as applied to polishing.
  • apparatus for enabling the formation, on an object (herein referred to as the specimen) of an aspheric or other curved surface of prescribed figure of revolution comprises means for mounting the specimen for rotation about a fixed axis, a grinding or polishing surface arranged for resiliently bearing against the surface of the specimen over an effective area of contact which is a mere fractional part of the desired surface of revolution, for example of the order of 5% or less, means for reciprocating said grinding or polishing surface in a general plane through the fixed axis, means for causing the grinding or polishing surface to assume, or at least tend to assume, substantially such orientation about an axis at right angles to the plane of reciprocation at any location in its traverse as it would have for the same location in its traverse in contact with the surface of prescribed figure.
  • the part of the grinding or polishing surface which is at any time efiective wholly or mainly in removing material from the specimen, will be dependent upon the amount by which the slope of "the part of the specimen against which the grinding or polishing surface bears, differs from the nominal s'l'ope for that part of the surface'o'f prescribed figure.
  • this orientation control is that. when the grinding or polishing surface is traversing a, hill on the specimen, that .is an annular zone of excess height on the specimen, the grinding or polishing surface begins to make effective contact with the rising flank of the hill sooner, makes effective contact with the crest of the hill longer and continues to make effective contact with the nether -flank of the hill longer than it would otherwise do in the absence of orientation control. "Correspondingly the grinding or polishing surface Elingers for a shorter time in effective contact with the bottom of a valley than it would in the absence of orientation control.
  • the grinding or polishing surface :per so may :be provided in any suitable manner, but preferably as a replaceable pad conveniently secured to, or in some cases resiliently-mounted ion: or in, a holder.
  • the rod ,or bar may b fSBCUIEd to the pad, or holder, so as initially-that is ibefore wear sets into extend normally to the tangent plane of contact surface of said pad, the cam means being a cam of profile whichis the evolute of the surface of prescribed figure.
  • the cam wear will "be negligible; moreover, if the rod or bar is normal to the surface of the pad, there will be no necessity for the cam means to be displaced relatively -to the pad or its support in order-to compensate for wear on the pad, namely properly to locate the cam with respect to the contact surface of the pad as it becomes worn in service.
  • the required evolute cam for use in the formation of any surface of prescribed figure may be constructed in any convenient manner.
  • Such cam may conveniently be defined by the law relating the angle made by the tangent with the axis of the specimen and the axial position of the intersection of that tangent with the tangent parallel to the axis; with a multiplicity of such tangents drawn in convenient manner, their envelope will provide the desired cam profile. It will be appreciated that errors in cam shape-although tending to reflect as corresponding errors in the shape formed on the specimen do not pre clude the attainment of the prescribed surface albeit at the costof increased intelligent supervision and local zonal use of a grinding or polishing pad.
  • the grinding or polishing surface may be biased in the direction for engagement with the specimen by any suitable means, such for example as by'spring means and/or-gravity, capable of ensuring light, and fairly uniform, contact pressure within the limits of positional freedom of the pad in the plane of reciprocation, such as to be substantially unaffected by hills or valleys on the surface which is being formed to thedesired shape.
  • suitable means such for example as by'spring means and/or-gravity, capable of ensuring light, and fairly uniform, contact pressure within the limits of positional freedom of the pad in the plane of reciprocation, such as to be substantially unaffected by hills or valleys on the surface which is being formed to thedesired shape.
  • the grinding or polishing pad may lee-mounted, either'directly or throughrspring means, upon a bar or rod-suitably pivoted to a connecting rod, or equivalent linkage, which in turn is pivoted to a. reciprocating member or carriage; a, rod or bar attached to said pivoted supporting bar may then co-operate with evolute-carn means to provide the aforesaid orientation control.
  • the cam means employed in effecting orientation control of the grinding or polishing pad may be such that the shape may be distorted, for example'under screw control, as and when required; such distortion may be effected in order that secondary effects, if such are found to affect seriously the nominal shape which tends to be produced on the specimen, may be compensated, or alternatively so that if a prototype has al ready been made, the cam shape maybe adjusted until the contact area or its optical equivalent (which can be observed on polished surfaces by methods akin to autocollimation or by Newtons rings) remains fixed with respect to the grinding .nr polishing pad during the traversing thereof.
  • the cam means may include two branches appropriately spaced apart so that the normal rod :above referred to :rolls first along one surface and then becomes transferred for rolling along'th'e other surface.
  • the pinor roller-carrying rod may conveniently, but not of necessity, lie approximately in the plane of the contact surface. It may be necessary to provide means for moving the pin or roller with respect to the rod to keep it in the plane of the contact surface, as the pad wears.
  • a rod or bar attached to the grinding or polishing pad, or its support to slide with respect to a connecting rod the length of which, and the length of the crank of which, are adjustable.
  • an aspheric surface of revolution it will generally be convenient to commence with a nominally spherical surface or at least a surface having revolution.
  • the nominally spherical or other surface of revolution should be polished, at least to some extent, in order to facilitate the use of optical tests in effecting the lining up of the specimen with its axis, for example the particular radius of the sphere which passes perpendicular to the rim, or, in the case of a lens the particular radius of the surface to be ground or polished, which passes through the centre of the other surface, coincident with the axis of mounting.
  • Figs. 1 and 2 are elevation and plan views respectively, and Fig. 3 an en- L larged fragmentary view of a detail, for an apparatus arranged in accordance with the invention for use in providing lenses with aspheric surfaces of figure of revolution.
  • the lens which is to be formed with a surface of prescribed figure of revolution is indicated at I as being seated in a cell 2 which is mounted on a hollow spindle 3 journalled in bearing 4 for rotation without shake, wobble or nutation precession about a vertical axis.
  • Pivotally mounted above spindle 3 for rotation about a horizontal axis is a bar 5 to the underside of which is fastened the grinding or polishing pad 6 so that its centre lies substantially in alignment with the pivotal axis of bar 5.
  • the pivots for the bar 5 are carried on a floating pair of links 8 pivoted at 9 to a carriage l which is guided in-slides II for horizontal movement on traverse table l2.
  • the carriage Ill may be arranged for reciprocation in an convenient manner but preferably under continuous control as regards the mean position of the reciprocatory traverse and in some cases as regards its amplitude.
  • link I pivoted at It to the carriage l0 carries pin I! which engages in arcuate groove I8a in lever H3, said pin i? being releasably locked in any desired position in said groove, for example by means of a butterfly wing nut I la.
  • said lever 18 is pivoted to a link [9 which is coupled with crank 20 attached to shaft 2
  • Adjacent its other end said lever I8 is pivoted at IBZ) to a bar 22 which is guided in slide 23 for horizontal movement on an extension of the traverse table l2.
  • Attached to said bar 22 is a nut 2 riding on a screwed rod 25 which is arranged for continuous rotation by servo-motor 25.
  • the lever l8 will be rocked about pivot l8b accordingly to act through link 55 for moving the carriage ID to and fro to an extent which is determined by the position of adjustment of pin l! in groove l8a.
  • servo-motor 2E rotating, the nut 24 and thus bar 22 and pivot lBb will be continuously advanced or retracted, according to the direction of rotation of said motor, so as to cause the mean position of said to-and-fro motion of the carriage to creep either to the left or right in the drawing according to the direction of rotation of motor 25,
  • the operation of the servo-motor 26 will be suitably controlled, for instance by limit switch means, so that creeping of the mean position of the reciprocatory carriage i0 is effected between preset limits.
  • the pad-bar 5 will be correspond ngly moved, namely to carry the grinding or polishing pad 6 over the surface of the lens in a succession of reciprocatory sweeps whose mean position is being continuously varied, for instance movin outwardly from the axis to the rim of the lens I or vice versa.
  • the grinding or polishing pad 6 is of construction hereinbefore referred to; as regards its size it may be mentioned by way of example that for the lens I being required to have an aspheric surface approximately paraboloidal and of paraxial radius of curvature 3.2 cm. convex and of overall diameter 6.4 cm., polishing pads ranging from 3 mm. x 5 mm. to 6 mm, x 10 mm. are contemplated.
  • the pad 6 is intended to bear resiliently against the surface of the lens 5 being operated upon and this may be effected under gravity but preferably is assisted by the action of spring 28 attached at one end to carriage it while its other end bears against a lug 5a projecting transversely from the pad-bar 5 to which said lug is fast.
  • a rod 29 Rigidly connected to the pad-bar 5 is a rod 29 herein referred to as the normal rod, being nominally perpendicular to the tangent plane at the centre of that surface of the pad 5 which is adapted to contact with the lens i.
  • a cam 3% For engagement by the normal rod 29 is a cam 3% having shaped surface Slla whose profile is the evolute of the prescribed surface to-be formed on the lens 1.
  • Said cam 30 is provided with universal mounting 3!, namely, to enable horizontal and vertical adjustment of said cam. It is essential that the normal rod 29 be attached to the pad-bar 5 so that the location of engagement with the cam surface 30a is coplanar with the pivotal axis of the pad-bar 5.
  • the normal rod 29 is resiliently urged into engagement with the cam surface 390.
  • the pad 6 will preferably beset at. about. 701%;- of the; radius; since the largest height of glassmustlbe removed from the zone.
  • the motion of thertraverse ing carriage Iii will be adjusted to provide a traverse of /2 cm. for a pad 6 having. a contact surface which is initially plane and is. ct about. 1 cm; square.
  • the spindle 3 supporting: thexlensl and. the shaft 2.! for effecting reciprocation.
  • the area of effective contactbetween the pad 6 and lens I wasvinitially much; smaller than the pad and moved with respect to the pad during the traverse of the latter owing to the great height at the true figure of the 70% zone; soon the contact area had extended over most of the pad 8 while this was in mid traverse, but towards the extremities of the traverse more than half of the pad was notcontacting' the lens at all, being manifest by the nonremoval of the pencil lines; the machine could safely be left operating until thepencillines had vanished up to the limit of the traverse; wher upon the traverse was increased, forinstance-by adjustment of the position of the pin H in the a groove mo.
  • optical tests for example the Fou cault knife-edge test
  • the Fou cault knife-edge test should be applied at frequent intervals during grinding or polishing and the pad traverse stroke and creeping limits accordingly adjusted without removing the specimen from the spindle.
  • a screen 32 formed with a pin-hole 32a, and a lens 33 suitably mounted coaxially with said lens i by means of tube 36 in which said lens is seated and which is secured to said screen 32; the light beam for carrying out the test being arranged to be pro jected through the hollow' spindle 3 on to thelens 33'.
  • The: apparatus is: applicable either in the: for-- mation of concave or convex; surfaces; It will generally be round to conduct to faster grinding if: the grinding or polishing pad is loaded so that the centre of pressure is nearer to the trailing than the leading edge.
  • the ins vention may also beused to makeother shapes: of. revolution, for-example, a portion. of a. conic, including the pole, rotated about a lineperpen-- dicular to its major axis.
  • Such shapes may be; convenient asgauges in work'with aspheric lenses (for example a profile gauge consisting of a hyperboloid of one sheet, to test a convex: lens which is one sheet of a hyperboloid of two: sheets).
  • Apparatus for grinding and/or polishing a lens to'form thereon an asphericv surface of prescribed fi'gure of revolution, comprising means for mounting the lensfor rotation about a fixedvertical axis, a bar pivoted about" a horizontal axis to a carriage which is arranged for horizontal reciprocation towards and away from the said vertical axis, a grinding or polishing pad secured to the underside of the said bar and arranged for presenting a grinding or polishing surface to the lens which is small, for example 5% or less, in relation to the surface of prescribed figure,
  • Apparatus as defined in claim 1' including means for adjusting the mean position of reciprocation ofxsaid grinding. or polishing surface. relatively to the axis of rotation of said lens.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)
US668124A 1945-03-19 1946-05-08 Formation of curved surfaces of prescribed figure by grinding and/or polishing Expired - Lifetime US2435126A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2435126X 1945-03-19

Publications (1)

Publication Number Publication Date
US2435126A true US2435126A (en) 1948-01-27

Family

ID=10906850

Family Applications (1)

Application Number Title Priority Date Filing Date
US668124A Expired - Lifetime US2435126A (en) 1945-03-19 1946-05-08 Formation of curved surfaces of prescribed figure by grinding and/or polishing

Country Status (2)

Country Link
US (1) US2435126A (enrdf_load_stackoverflow)
BE (1) BE476819A (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
US3203138A (en) * 1963-07-08 1965-08-31 Dresser Ind Apparatus for producing aspheric surfaces
US4216626A (en) * 1977-05-13 1980-08-12 Prontor-Werk Alfred Gauthier G.M.B.H. Machine for grinding and polishing workpieces

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US547138A (en) * 1895-10-01 Apparatus for forming curved surfaces
GB190704527A (en) * 1906-03-16 1907-12-19 Georges Arsene Ossart Improvements in and relating to the Manufacture of Optical Lenses.
US995393A (en) * 1909-12-27 1911-06-13 Samuel Witmer Machine for grinding variable curves.
GB191503354A (en) * 1915-03-02 1915-12-09 Ernest Miles Taylor New or Improved Means for the Manufacture of Optical Lenses.

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US547138A (en) * 1895-10-01 Apparatus for forming curved surfaces
GB190704527A (en) * 1906-03-16 1907-12-19 Georges Arsene Ossart Improvements in and relating to the Manufacture of Optical Lenses.
US995393A (en) * 1909-12-27 1911-06-13 Samuel Witmer Machine for grinding variable curves.
GB191503354A (en) * 1915-03-02 1915-12-09 Ernest Miles Taylor New or Improved Means for the Manufacture of Optical Lenses.

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
US3203138A (en) * 1963-07-08 1965-08-31 Dresser Ind Apparatus for producing aspheric surfaces
US4216626A (en) * 1977-05-13 1980-08-12 Prontor-Werk Alfred Gauthier G.M.B.H. Machine for grinding and polishing workpieces

Also Published As

Publication number Publication date
BE476819A (enrdf_load_stackoverflow)

Similar Documents

Publication Publication Date Title
US1325789A (en) johnsson
US2435126A (en) Formation of curved surfaces of prescribed figure by grinding and/or polishing
US1901181A (en) Toric lens generating machine
US2419543A (en) Means and methods of abrading
ES359168A1 (es) Un metodo y un aparato para generar, rectificar o pulir su-perficies asfericas de revolucion.
US2470021A (en) Grinding and polishing machine
US1343522A (en) Process for grinding and polishing lenses
US2359704A (en) Forming guide for engraving machines
US995393A (en) Machine for grinding variable curves.
US2337183A (en) Honing device
US2510113A (en) Machine for grinding lenses
US5116391A (en) Curved surface rubbing apparatus
US1599405A (en) Machine for generating toric surfaces on lenses
US1458938A (en) Knife sharpener
US1286032A (en) Art of forming curved surfaces.
US2105175A (en) Method and means for abrading lenses
US1702267A (en) miller
US2411591A (en) Drill grinder
US1318300A (en)
US1515681A (en) Lens grinder
US2065103A (en) Lens grinding machine
US1800308A (en) Lens-surfacing machine
US2822649A (en) Profile grinder
US1827368A (en) Lens edging machine
US2458384A (en) Grinding of lenses or of dies therefor