FR2528748A1 - MACHINE FOR MACHINING CURVED SURFACES - Google Patents

Abstract

MACHINE FOR MACHINING CURVED SURFACES, IN PARTICULAR SURFACES OF TORIC-SHAPED OPTICAL LENSES, OR ASPHERIC LENSES OF REVOLUTION OF THE TYPE INCLUDING IN A FRAME A FIRST SUPPORT FOR A ROTATING CUTTING TOOL. SPINDLE 35 OF CUTTING TOOL 38 IS FIXED TO A SECOND SUPPORT 25 DRIVEN IN ROTATION AROUND AN AXIS 23 CARRIED BY A THIRD SUPPORT 18 SUITABLE TO MOVE ACCORDING TO TWO ORTHOGONAL AXES. APPLICATION TO THE REALIZATION BY GRINDING OF SURFACES OF LENSES OR MOLDS FOR LENSES.

Description

MACHINE FOR MACHINING CURVED SURFACES

  The present invention applies to a machine intended for machining

  curved surfaces, in particular concave toric surfaces or

  vexes or aspherical surfaces of revolution on a piece made of a material adapted to its use and such as organic or mineral glasses, using a cutting tool such as an abrasive bandwheel grinding wheel or

a spherical wheel.

  Numerous machines of this type have already been produced, including in an automated or semi-automated version. Among these embodiments, one of the most remarkable described in French Patent 2 204 987 provides for a disposition of the workpiece on a support according to a vertical axis coincides with the optical axis of the lens to be machined and a rotating tool whose pin is arranged vertically in front of the workpiece.

  machining, this spindle performs a pivoting movement

  turn of an axis passing through the grinding wheel The work support is subjected to a double movement in two orthogonal directions located

  in a plane perpendicular to the rocking axis of the grinding wheel.

  This arrangement of the machine to machine the toric surfaces of the optical glasses has, beside undeniable advantages of compactness and

  reliability, various disadvantages in the operating conditions

  machines, especially in terms of speed and speed.

  machining decision When changing the grinding wheel, it is necessary to adjust the spindle of the grinding wheel to place the swing axis on the strip

  of the new wheel and such a setting is very difficult to achieve.

  For the machining of surfaces from lenses to strong

  curvature, it is necessary to return from 1800 the glass in the course of

  The wheel spindle abuts the edge of the glass in the case of machining the concave surfaces or the grinding wheel abutment abuts on the glass spindle in the case of machining the convex surfaces.

  In addition, this machine requires a reversal of

  then lowering) guiding parts, which causes an addition of mechanical games detrimental to precision The known type of machines are generally not equipped with means of loading and unloading-

  automatic parts that only allow a large machining rate.

  In addition, the provisions of existing machining machines lead the machined and abrasive particles to spill.

  on fragile and abrasion-sensitive steering equipment.

  One of the aims of the present invention is precisely to mitigate

  these difficulties and inadequacies of the existing machines while preserving

  the reliability and compactness of the equipment known to the

same kind.

  For this purpose, the machine for machining curved surfaces on a workpiece, in particular surfaces of optical lenses or lens molds, of the type comprising in a frame a first support of a rotary cutting tool which has a cutting edge. intended to come in

  contact with the curved surface to be machined, is characterized in that the bro-

  the cutting tool and its drive means are fixed rigidly

  to a second support driven during machining by a system * controlled numerically (CNC) in rotation about an axis of rotation which is perpendicular to the axis of rotation of the cutting tool, the second support being himself carried by a third support which, during

  machining, moves in numerical control (CNC) along two orthogonal axes

  and to the axis of rotation of the second support for positioning this axis of rotation of the second support and so as to generate the curved surface of the workpiece by the cutting edge of the cutting tool and in that the main axis of the cutting tool and that of the surface of the

  the lens being machined are arranged in the same sensitive plane

  horizontally so as to allow the machining

  easy removal of abrasive particles from the cutting tool and / or workpiece material from the cutting tool support pin and

  to ensure high rigidity at the spindle of the cutting tool The third

  sth support is protected from abrasive particles from the cutting tool

  and / or material of the workpiece by a housing with telescopic elements

  nests interlocked into one another and able to discharge the liquid

  cooling of the cutting tool and the abrasive particles

  out of the area of the steering and rotation mechanisms of the second

support me.

  According to a preferred embodiment, the axis of rotation of the second

  my support is located in front of the cutting tool.

  According to an embodiment used for the machining of the O-rings of revolution, the workpiece is held fixed on the head of a workpiece support. For the machining of aspherical surfaces of revolution, the workpiece can be driven in rotation about its optical axis and / or

  revolution while the cutting tool moves in two orthogonal planes.

  According to another embodiment of the invention, the workpiece

  ner, such as a block of glass, is carried by a head of a rotating support

  revolver type of several successive positions and of which one of the heads is in a first position corresponding to the horizontal axis of the workpiece in the machining position, while at least one other head is in a second position corresponding to a loading station and / or

  control and / or unloading of workpieces or machined.

  In a variant, the rotary support is mounted on an axis integral with the frame and supports geometric control means for the curved surface.

  to be machined The checkpoint comprises means of geometric control

  which are preferably optical and / or optoelectronic means for the machined surface and electrically and / or electronically coupled

  means for controlling the movements of the second and third supports.

  The geometric control means can be pointed at the surface of the machined part which is carried by one of the heads of the rotary support

  brought into the control position According to a more com-

  plex, when the control means detect a defect in the surface after machining the workpiece, recovery means trigger a new

  moving from the workpiece to the machining position.

  The workpiece may be fixed projecting on one of the heads of the rotary support by means of one-sided fastening means such as vacuum suction cup, coupled to a locating pin of its axial position. According to a highly automated embodiment of the invention, the axis of the rotatable support integral with the frame or the spindle of the cutting tool is equipped with means for controlling the geometry of the cutting tool such that wheel and able to trigger a profile rectification phase

  of the cutting tool when this profile is degraded.

  control of the geometry of the cutting tool are coupled to the means of com-

  digital control (CNC) of the second and third supports to cause a correction of the path of the cutting edge of the tool according to

wear of it.

  Other objects, advantages and features of the invention are

  read the description of an embodiment of a

  machine according to the invention for the machining of eyeglass lenses, made in a nonlimiting manner and with reference to the attached drawing o: FIG. 1 is a sectional view of the whole machine according to the invention for machining toric surfaces of optical lenses; Figure 2 is an enlarged plan view and top cover removed from the center of the machine of Figure 1; Figure 3 is a sectional view along the plane III of Figure 1, the mechanism of rotation of the machine table, this mechanism being shown on a larger scale still; Figures 4 and 5 show in top view and in section, the different positions of the wheel of the machine during the machining of a concave surface and respectively a convex surface of optical lens; FIG. 6 is likewise seen in plan view and in section two theoretical limit positions of the grinding wheel of the machine during the machining of a concave lens surface with a small radius of curvature; FIG. 7 represents a top view and a partial section of a machining pass of an aspherical surface of revolution.

  using the machine according to the invention.

  The machine for machining the toric surfaces according to the invention comprises a rigid frame consisting of a base 1 on which are assembled amounts 2 and 3 which laterally support sealing plates

  4 and 5 The base 1 mounted itself on a base placed on the ground, sup-

  carries supports 6 and 7 of two transverse guide axes 8 and 9 of a

  base support 10 capable of moving transversely by the in-

  intermediate of bearings 11 and 12 and under the action of a translation screw

  13 screwed into a nut (not shown) secured to the support 10 and

  rotational drag through a belt or chain 14 coupled to a reversible electric drive motor 15 controlled by a digital control system connected to a computer or a control center.

  calculation and control (CNC) of the machine.

  The base support 10 supports, by bearings, guide bars 16 on which is slidably mounted by bearings 17, only one of which is shown, a steerable support (or third support) 18 relatively rigid The support 18 can move longitudinally

  on the bars 16 under the action of a screw 19 screwed into a tubular nut.

  20 and can be rotated by means of an electric longitudinal translation motor 21 to which it is coupled by a chain or a toothed belt 22 Like the motor 15, the motor 21 is reversible and controlled by a system numerical control

  connected to the center of calculation and control of the machine.

  The steerable support 18 contains a rotating shaft 23 of strong

  section and whose axis is shown in the sectional plane of Figure 1.

  This shaft 23 is guided by large roller bearings 24 and carries the machining table 25 of the machine which constitutes a second support and is extended by flanged sealing plates 26 and 27 fitted into corresponding flanges 28 and 29. other sealing plates 30 and 31 integral with the orientable support 18 To complete the sealing of the mechanisms carried by the support 18 with respect to the cutting liquid poured by a pump into the machining area, flanges 32 and 33 plates

  and 31 are telescopically interlocked on

  The machining table 25 is extended by a strongly ribbed pin support 34 which carries the rigid pin 35 of a grinding wheel rotated by a spindle motor 36 (see FIG.

  it is preferably connected by a belt 36. The cone of ac-

  coupling 37 of the pin 35 can receive various types of bush wheels

  38 equipped with abrasive bands of diameters adapted to the radii R of the sur-

lens faces to be machined.

  According to the invention, the spindle 35 and its drive motor 36 are rigidly fixed to the support 34 itself secured to the machining table 25 which can rotate under the action of a screw 39 acting on a ring gear 39 is secured to the shaft 23 Referring to Figure 3, we see that the screw 39 is connected by a chain or a toothed belt 40 to a reversible electric motor 41 drive

  in rotation flanged on the orientable support 18.

  According to another important aspect of the invention, the workpiece formed, in the embodiment described, of a glass block 42

  is arranged with its main optical axis in a horizontal plane

  The workpiece 42 is carried by one of the multi-position heads 43 of a revolving rotary support 44 mounted on a guide pin 45.

  attached to the upright 2 by a support flange 46.

  A station 48 for automatic loading and unloading of the workpieces is provided opposite the head 47 in the position shown in FIG. 1 A station 49 for geometrically controlling the machined surfaces

  is also provided opposite the head 47 in its position shown.

  The geometric control means may be constituted by optical and / or optoelectronic means such as a photocell.

  coupled to one or more sensors connected to the computer and

  In the same way, the spindle 35 or another part of the machine, integral with the spindle, can be equipped with means 51 for controlling the geometry of the active part of the grinding wheel.

  especially the diameter of its strip surface.

  The workpiece 42 is fixed projecting on the head 43 by all

  medium, preferably by a suction cup 52 and the posi-

  tion and / or the presence of the piece on the bearing face 53 of the head 43 can be identified by a probe 54 mechanically connected, if necessary,

  to a cam surface (not shown) of the guide pin 45.

  According to an important characteristic of the invention, the rotational axis

  55 of the shaft 23 (and thus of the machining table 25 of the pin 35 and the grinding wheel 38) is perpendicular to the axis of rotation of the grinding wheel 38 and is preferably located in front of the wheel 38 relative to the

  pin 35, as shown, regardless of the overall lens surface

  the concave or convex axis, the axis of rotation 55 moving during

  each machining pass with respect to the curved surface to be machined 50.

  FIG. 2 is a cross-sectional view of various types of cup wheels of different diameters (38 a, 38 b, 38 c) used for the generation of lens surfaces in the mini-rays and

  maxi of the toric surfaces to be machined.

  To explain the operation of the machine for machining

  lens faces shown in FIGS. 1 to 3, reference will first be made to FIGS. 4 to 6 which represent on a large scale different positions

  between the active surface of a grinding wheel 38 and the lens surface

  In FIG. 4, there is shown in the horizontal plane of the axis of the spindle 35 three successive positions of a grinding wheel 38b.

  mean diameter grinding the concave surface 50 of a lens 42.

  The strip surface 56 of the grinding wheel 38b comes into contact with the concave surface 50, by a curved tangent line shown in projection in FIG. 4, by a line 57. This curved tangent line must be kept identical to itself. even during machining to form the toric surface 50 and for this the angle e that makes the axis of the grinding wheel with the perpendicular to the surface 50 at the machining point must be constant during the pass of machining This constancy of

  the angle e can easily be respected by the numerical control of rotation

tation of the tree 23.

  FIG. 5 shows the machining of the convex face 50 of an aperture lens a and of larger outer radius R, by a grinding wheel 38b of mean diameter. engaging inside the grinding wheel headband without coming into contact with the inner face 58 of the headband. The machining of the convex surface 50 can thus be made in one pass and the band surface 56 wraps around the curved tangent line. through the inside of the headband kept at a

fixed radius r.

  In FIG. 6, two grinding wheel positions are shown during the machining of the concave inner surface 50 of a lens 42 of greater radius of curvature R The strip surface 56 of the grinding wheel 38b envelops the surface 50 on a long, very curved tangent line, and it will be seen that the grinding spindle will come into contact with the upper edge of the lens 42 if the relative movement of the grinding wheel 38b is continued towards the bottom of FIG. therefore necessary to achieve

  the machining of the convex surface 50 in two separate passes which connect

  preferably in the center of the surface 50 while still maintaining the

  tilt angle O of the wheel axis with the normal to the surface 50 at the machining point, so as to maintain a constant curved tangent line. FIG. 7 schematically represents a machining pass of a

  convex aspherical surface of revolution In this variant of

  the machine according to the invention, the workpiece 42 fixed at the end of one of the heads (43, 47) is rotated around its

  Y'X optical axis The corresponding drive means are at the door

  Those skilled in the art and are not shown in detail in this figure The machining of such a surface can be carried out by means of grinders of the bushel type (38 a, 38 b, 38 c) or even way of a wheel

  with spherical strip 38 d as shown For a spherical strip wheel

  38 d, the axis of the grinding spindle will be horizontal and perpendicular.

  Figure 7 shows by way of example two positions of the grinding wheel 38 d for which the axis of rotation of the grinding wheel is perpendicular to the normal to the generator.

from the surface to the point considered.

  To carry out a machining operation of a toric surface on the machine according to the invention, the operator 48 has a rough glass to be machined 59 on the seal of the support head 47 and, after being depressed

  of the corresponding vacuum chamber 52, the raw glass 59 is rigid.

  held on the head 47 After completion of the machining of the

  this 42 being machined on the machine, the rotary support 44 pivots and brings the machined part 42 to the unloading and control station and the

  piece 59 in the machining position.

  The machining table 25 has been moved back to the position shown in FIG. 1. At the start of the machining cycle, the grinding wheel 38 is already rotated and the longitudinal translation motor 21 is started by the center. numerical control calculation, in

  the direction of advance of the grinding wheel 38 towards the surface to be machined 50.

  The rotary drive motor 41 is also started to rotate the machining table and orient the spindle axis.

  in order to respect the angle of attack of the surface 50 by the sur-

  Likewise, the motor 15 is shown in FIG.

  by the numerical control system so as to bring the edge of the

  sineuse of the strip surface 56 of the grinding wheel at the edge of the surface 50

  to machine on the piece 42, this leading edge of the machining being, for example

  plotted by the photocell of the geometric control means

51.

  As soon as the grinding wheel 38 is positioned, the numerical control system

  the machine triggers successive machining passes of the machine.

  strip face 56 of the grinding wheel 38 along the curved tangent line 57

  presented in FIGS. 4 and 5 by simultaneous rotation of the motors 15,

  21 and 41 coordinated by the numerical control system, until the

  geometry required for the surface 50 The machining table

  25 is then returned to the position of Figure 1 to allow the rotation of the revolver support 44 and the continuation of the machining process

on another blank 59.

  The machine for machining lens surfaces according to the invention

  tion makes it possible to ensure a much greater machining rate and greater reliability than known type machines, mainly thanks to the revolver support 44, to the protection of its internal mechanisms by the housing with telescopic elements 4, 5, 30 , 31, and at the highest rigidity

of its constituents.

  The machining of the lens surfaces takes place through successful passes.

  discontinuations carried out continuously without interruption until the final and final score is obtained, even for high-c lens surfaces. for which the change-over of the grinding wheel is carried out automatically under the control of the numerical control. The machining of the surface 50 can be carried out in two passes after a precise dimensional control with regard to The finishing pass can be performed, for example, after the roughing of the surface of another part 42 The machining of an aspherical surface of revolution is done according to the same process as that of the 'machining

of a toric surface.

  Of course, the invention is not limited to the embodiments described and shown and is capable of numerous variants accessible to those skilled in the art, without one deviating from the spirit of the art. 'invention.

  Thus the mechanical control of displacement by electric motors

  According to two axes of orientation and in rotation of the machining table: 25 could be achieved by any equivalent means such as hydraulic cylinders or other coupled and coordinated by a numerical control system.

Claims (9)

  1. Machine for machining curved surfaces on a workpiece, especially   particular, surfaces of optical lenses or lens molds of the type comprising in a frame: a first support of a rotary cutting tool which has a cutting edge intended to come into contact with   the curved surface to be machined, characterized in that the spindle (35) of the   cutting tool (38) and its drive means (36) are rigidly attached to a second support (25) driven during machining by a CNC system, rotating about an axis of rotation. rotation (55) which is perpendicular to the axis of rotation of the cutting tool (38), the second support (25) itself being carried by a third support (18) which during machining is moves in numerical control (CNC) along two axes orthogonal to each other and to the axis of rotation (55) to position   this axis of rotation (55) of the second support (25) so as to generate   draw the curved surface (50) of the workpiece (42) by the cutting edge of the   and in that the main axis of the cutting tool (38) and that of the surface (50) of the lens (42) being machined are arranged in a same substantially horizontal plane so as to allow, during   machining, easy removal of the abrasive particles from the cutting tool   pe (38) and / or material of the workpiece (42) out of the support pin (35) of the cutting tool and to ensure high rigidity of the   pin (35) of the cutting tool (38).   2. Machine according to claim 1, characterized in that the axis   rotation (55) is located in front of the cutting tool (38).   Machine according to claim 1 or 2, in particular for machining toric surfaces and having a cutting tool in form   bowl, such as a bushel wheel, characterized in that during the   sinagela workpiece (42) is held fixed on the head (43) of a room support (44).   4 Machine according to one of claims 1 or 2, in particular   for machining aspherical surfaces of revolution, characterized in that the workpiece (42) is rotated about its axis   optical and / or revolution by the head (43) of a workpiece support (44).   5. Machine according to one of claims 1 to 4, characterized in   the third support (18) is protected from the abrasive particles of the cutting tool and / or the material of the workpiece by a nested telescopic element housing (4, 5, 30, 31). other and apt   to discharge coolant from the cutting tool and the   abrasive particles which it carries out of the zone of the mechanisms of orienta-   rotation and rotation of the second support (18).   6. Machine according to one of claims 1 to 5, characterized in   the workpiece (42), such as a block of glass, is carried by a head (43) of a revolver-type rotary support (44) at a plurality of successive positions and of which one (43) of the heads is in a first   position corresponding to the horizontal axis of the workpiece in the machined position.   ge, while at least one other head is in a second position cor-   corresponding to a loading station, and / or control and / or discharge-   parts to be machined or machined.   7. Machine according to claim 6, characterized in that the sup-   rotary port (44) is mounted on an axis (45) integral with the frame and supporting   means (49) for geometrically controlling the curved surface (50) to be machined.   8. Machine according to claim 7, characterized in that the   geometric control means (49) are optical and / or optically   electronics for the machined surface (50) and electrically and / or electronically coupled to the displacement control means of the second (25) and third (18) supports.   9. Machine according to claim 8, characterized in that the geometric control means (49) are pointed on the surface (50) of   the machined part which is carried by one of the heads of the rotating support   tif (44) brought into the control position.   Machine according to claim 9, characterized in that, when   that the geometric control means (49) detect a defect in the   face (50) after machining the workpiece (42), return means triggers   a new passage of the piece (42) in the machining position.   He. Machine according to one of claims 3 to 10, characterized   that the workpiece (42) is projectingly attached to one of the heads (43) of the workpiece support (44) by means of a one-sided fastening means such as a vacuum suction cup (52). ), coupled to a tracking probe (54) of its axial position -   Machine according to one of Claims 1 to 11, characterized in that   the spindle (35) of the cutting tool is equipped with means (51) for controlling the geometry of the cutting tool (38) such as a grinding wheel and able to trigger a grinding phase of the cutting profile. the cutting tool   (38) when this profile is degraded.   13. Machine according to claim 12, characterized in that the control means (51) of the geometry of the cutting tool are coupled to the numerical control means (CNC) of the second (25) and third (18) supports to cause a correction of the path of the cutting edge   (56) of the tool (38) according to the wear thereof.