Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
  • B23Q1/00—Members which are comprised in the general build-up of a form of machine, particularly relatively large fixed members
  • B23Q1/25—Movable or adjustable work or tool supports
  • B23Q1/44—Movable or adjustable work or tool supports using particular mechanisms
  • B23Q1/48—Movable or adjustable work or tool supports using particular mechanisms with sliding pairs and rotating pairs
• • 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
  • B24B13/04—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 involving grinding wheels controlled by gearing
  • B24B13/043—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 involving grinding wheels controlled by gearing using cup-type grinding wheels
• • 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

Definitions

• the invention relates to a machine and a method for generating by grinding any surface - in particular off-center and / or prismatic - of optical or ophthalmic lens made of organic or mineral glass.
• European patent application EP-0 176 894 describes a machine generating toric lenses controlled from a computer and an associated memory in which are stored different discrete machine setting values corresponding to different shapes of toric surfaces generated.
• this machine does not generate aspherical or parabolic surfaces.
• this machine requires perfect centering of the lens on its support and does not allow the peripheral edges (clipping or beveling) of the lens to be machined directly.
• this document aims to reduce the elliptical error and plans to do this several grinding passes, each pass consisting of a rotation of the grinding wheel support around the center of the base circle of the toric surface to be generated, the wheel being tilted to generate the cylinder curve.
• the computer supplies control signals to stepping motors which perform position adjustments before each grinding pass, making it possible in particular to adjust the relative distance between the grinding wheel and the lens and the orientation of the grinding wheel.
• the implementation of such theoretical teaching nevertheless poses the crucial problem of the precision of the adjustments and the grinding. Indeed, while one wants to correct the elliptical error which corresponds to errors of the order of a hundredth of a millimeter, the use of simple stepper motors to control the axes of movement already provides a position error of the order of a tenth of a millimeter.
• the adjustment values stored in the stored tables being discrete, it is not possible to make a fine adjustment between two discrete values, and to machine any shape of toric surface.
• machines generating mineral glass lenses require the use of a grinding wheel whose abrasive part is in the general shape of a rotating crown to define a circular cutting edge and which is mounted on its rotating support around an axis of rotation perpendicular to a pivot axis of the support.
• a grinding wheel whose abrasive part is in the general shape of a rotating crown to define a circular cutting edge and which is mounted on its rotating support around an axis of rotation perpendicular to a pivot axis of the support.
• the shape of such a grinding wheel described for example in patents FR-A-2 204 987 or EP-A-0 176 894 makes it possible to easily generate the toric surfaces on mineral glass by considerably reducing the problems of wear and allowing to take into account errors possibly caused by the wear of the grinding wheel.
• the need arises to be able to generate any surfaces on lenses which can be as well in mineral glass as in organic glass and this in a simple and inexpensive way, that is to say with a cost equivalent to that of prescription lens generation machines already known.
• the need also arises feel to design a prescription generation machine that can be integrated into an automated production process, and on which the maximum amount of work can be done, in particular trimming or beveling work.
• the object of the invention is therefore to propose such a machine for generating prescription lenses which is fully automated and allows the generation by grinding of all kinds, all shapes and all dimensions of mineral glass lenses.
• the subject of the invention is such a machine providing precision of the order of a hundredth of a millimeter or less, and at a lower cost.
• the invention also aims to provide such a machine which allows the realization of all surface shapes (toric, spherical, centered or not, prismatic •••) on a mineral glass lens, the parameters defining this surface may vary in continued.
• the object of the invention is to allow the production of lenses made of decentered mineral glass, or prismatic in any direction, or the like, by simple programming of the machine without requiring delicate specific manual assemblies or adjustments prior to grinding.
• the object of the invention is also to propose such a machine which is sufficiently precise and reliable to effectively allow the elliptical error to be corrected.
• the invention also aims to provide such a machine whose operation is compatible with the specific environment for machining mineral glass lenses (glass and diamond dust, water, etc.).
• the invention also aims to provide such a machine in which the number of parts and components is low, and in which the parts and components which constitute it are simple and of low price.
• the object of the invention is also to propose such a machine which does not incorporate a position sensor, nor of an optical ruler or other complex and expensive means of position control, but of which all the axes of movement are nevertheless controlled in position and in speed with an accuracy of the order of a hundredth of a millimeter or less.
• the invention also aims to provide such a machine which is compact and small, simple and easy to use and maintain while being precise and stable in its precision, to allow its use for example in workshops or laboratories reduced size optics. Also, the invention aims to propose such a machine which is robust, can work in a difficult environment, and for example is not very sensitive to vibrations.
• the invention relates to a machine for generating by grinding any surface - in particular off-center and / or prismatic - of optical or ophthalmic lens made of organic or mineral glass, comprising a frame, a lens support and a rotating grinding wheel support movably mounted on the frame, means making it possible to carry out the movements of these supports, one with respect to the other, of pivoting along an axis YY 'of pivoting and in translation along two axes XX', ZZ 'of translation which define a plane perpendicular to the pivot axis, a grinding wheel whose abrasive part is in the general shape of a rotary crown to define a circular cutting edge and which is rotatably mounted on its support around a proper axis of rotation orthogonal to the 'YY axis of pivoting characterized in that it further comprises vertical offset means making it possible to offset the own axis of rotation of the grinding wheel relative to the plane defined by the axes XX', ZZ '
• the means the vertical offset means comprise means for tilting the axis of rotation of the grinding wheel relative to the plane defined by the axes XX ', ZZ' of translation.
• the vertical offset means comprise vertical translation means making it possible to carry out a movement in translation of the lens and grinding wheel supports relative to each other along an axis Yl, YY 'parallel or coincident with said pivot axis YY'.
• the vertical translation means are means making it possible to translate the lens support relative to the frame along an axis parallel to the pivot axis YY '.
• the vertical translation means are means making it possible to carry out a movement in translation of the grinding wheel support relative to the frame along the pivot axis YY '.
• the machine according to the invention further comprises axial pivoting means making it possible to carry out a movement of the supports relative to one another by pivoting around at least one ZZ 'of said translation axes.
• These axial pivoting means are means making it possible to pivot the lens support relative to the frame around this axis ZZ 'of translation.
• the axial pivoting means could be means making it possible to pivot the grinding wheel support relative to the frame around the axis ZZ 'of translation.
• the abrasive part of the grinding wheel has an angular cross section whose apex defines the cutting edge.
• the machine is characterized in combination in that the means making it possible to carry out the movements of the supports comprise means making it possible to carry out a pivoting movement of the grinding wheel support relative to the frame around the axis YY 'of pivoting which is tangent to the angular circular cutting edge of the grinding wheel, and means making it possible to carry out translational movements of the lens support relative to the frame along the axes XX ', ZZ' of translation which are perpendicular to each other other and orthogonal to the axis YY 'of pivoting of the grinding wheel support, the lens being mounted on the lens support with its thickness oriented along one of the translation axes ZZ' - in particular with this translation axis ZZ 'passing through its geometric center and / or at least substantially parallel or coincident with the optical axis of the opposite surface of the lens which is in contact with the lens support.
• the machine comprises motor means producing and controlling the movements of these supports by relation to the frame along the axes of translation and / or pivoting, and programmable means for controlling the motor means which comprise: input means and means for memorizing parameters defining the shape of the surface to be leveled; means for calculating the characteristics of different electrical control signals for the motor means as a function of the theoretical shape of the surface to be ground; and means for transmitting the various electrical control signals.
• Each motor means controlled by the programmable control means comprises a movable member driven in movement and means for controlling the closed loop of the position of the movable member, and the calculation means are programmed to determine the characteristics of the control signals by interpolating the speeds and accelerations between the different movements along the axes of translation and / or pivoting, the transmission means transmitting the signals according to a chronology defined by the calculation means.
• each motor means controlled by the programmable control means essentially consists of at least one hydraulic servo-amplifier device incorporating: a hydraulic actuating element comprising a movable member driven in movement; hydromechanical means forming a control loop for the position of the movable member; and an electric stepper motor driving the actuating element via a valve.
• a hydraulic actuating element comprising a movable member driven in movement
• hydromechanical means forming a control loop for the position of the movable member
• an electric stepper motor driving the actuating element via a valve.
• the programmable control means determine the characteristics of the control signals for each axis of movement during the grinding pass as a function of the path which must be traversed by the support concerned, the calculation means performing an interpolation of the speeds and accelerations of the different moving axes.
• the calculation means perform a linear polygonal interpolation of the speeds.
• the motor means drive both the lens support and the moving wheel support during each grinding pass under the control of the programmable control means.
• the calculation means are programmed to calculate the difference between the desired theoretical shape of the surface to be generated, and the shape generated during grinding.
• the calculation means calculate, before each grinding pass from programmed formulas, a plurality of theoretical points defining the theoretical shape of the surface to be generated as a function of the parameters entered and stored.
• the calculation means also calculate the geometric characteristics of the grinding (movement of the supports along their axes) according to the parameters entered and stored.
• the calculation means also calculate a plurality of generated points defining the shape generated by the geometric characteristics of the grinding.
• the calculation means calculate the difference between the theoretical and generated points corresponding two by two.
• the programmable control means return all the motor means to a reference position defining a geometric origin of the machine before each grinding pass, the calculation means determining the characteristics of the electric control signals to generate the movements of the supports from this geometric origin.
• the invention also relates to a method for generating by grinding any surface - in particular off-center and / or prismatic - of optical or ophthalmic lens made of organic or mineral glass, using a grinding wheel the abrasive part of which is generally rotating crown to define a circular cutting edge, and which is rotatably mounted on a grinding wheel support about an axis of rotation, in which the grinding wheel support and a lens support are moved relative to each other at least according to pivoting movements along an axis YY 'of pivoting and in translation along two axes XX', ZZ 'of translation which define a plane perpendicular to the axis YY' of pivoting, the own axis of rotation of the grinding wheel being orthogonal to the pivot axis YY ', characterized in that the axis of rotation of the grinding wheel is offset relative to the plane defined by said axes XX', ZZ 'of translation.
• the proper axis of rotation of the grinding wheel is inclined relative to the plane defined by the axes XX ', ZZ) of translation.
• the lens and grinding wheel supports are moved in translation relative to one another along an axis parallel or coincident with the pivot axis YY '.
• the lens and wheel supports are shifted before grinding by tilting the axis of proper rotation of the grinding wheel by a predetermined angle and / or by moving these supports by a predetermined distance in the direction of the axis YY 'of the axis parallel or coincident with pivoting, this angle and / or this distance of offset remaining constant during grinding.
• the own axis of rotation of the grinding wheel is offset relative to the plane defined by the translation axes during grinding according to the shape of the surface to be generated.
• the lens and grinding wheel supports are moved relative to each other by pivoting around one of the ZZ 'at least of the translation axes - in particular around the ZZ' axis passing through the - geometric center of the lens and / or at least substantially parallel or coincident with the optical axis of the opposite surface of the lens -.
• the lens and / or grinding wheel supports can be moved in pivoting around the axis ZZ 'before and / or after grinding the surface in order to machine the peripheral edges of the lens for example to produce a bevel or clipping.
• any kind of mineral glass lens can be produced in a simple and economical manner, in particular off-center or prismatic lenses, the angle and value of the prism of which are arbitrary.
• this result is achieved using the same technologies as those used in the generation of standard toric surfaces.
• the invention allows the production of a machine in which the movements generated during grinding are permanently controlled by the means programmable control, the position and speed of the different axes in motion being controlled with high precision and reliability (stability of precision).
• the machine according to the invention does not incorporate any sophisticated and expensive position or sensor device.
• the invention also relates to a machine or a method comprising in combination all or part of the characteristics mentioned described above or below.
• FIG. 1 is a top view of a machine according to a first embodiment of the invention
• FIG. 2 is an elevational view of a machine according to the embodiment of the invention of Figure l
• FIG. 3 is a block diagram illustrating the programmable control means and the motor means of a machine according to the embodiment of the invention of Figures 1 and 2
• FIG. 4 is a flowchart illustrating the operation of the calculation means during a grinding pass performed by a machine according to the invention
• FIG. 5 is a sectional view along the proper axis of rotation of a grinding wheel of a machine according to the invention
• FIGS. 6a, 6b, 6c are diagrams illustrating the kinematics of the movements of the axes of a machine respectively according to the first embodiment of the invention of Figures 1 to 3, and according to a second and a third embodiments of the invention.
• the invention relates to a machine 1 for generating by grinding any surface of optical or ophthalmic lens in organic or mineral glass, comprising a frame 2, a lens support 3, and a support for a rotary grinding wheel on which is mounted a grinding wheel 5 which rotates around an axis 6 of rotation.
• a motor 7 is mounted on the grinding wheel support 4 and is connected in rotation by a belt 8 to the rotating shaft 9 whose free end 10 supports the grinding wheel 5.
• the support 4 of the grinding wheel is pivotally mounted relative to the frame 2 about an axis YY ′ of pivoting which is orthogonal to the axis 6 of proper rotation of the grinding wheel 5.
• the rotary grinding wheel 5 has a circular cutting edge 42 and the abrasive part 106 of the grinding wheel 5 is in the general shape of a rotating crown which has an angular cross section whose apex defines the cutting edge 42.
• the contact between the lens and the cutting edge 42 rotating in rotation about the axis 6 is made according to a portion of the circle defined by the trace of the circular cutting edge 42 when it rotates.
• the grinding wheel 5 is in contact with the lens according to a and a single contact line.
• the diameter of the cutting edge 42 is greater than the diameter of the lens to be ground.
• the axis YY ′ of pivoting of the grinding wheel support 4 is tangent to the circle defined by the angular circular cutting edge 42.
• the lens support 3 is mounted movable at least in translation along two axes XX ′, ZZ 'perpendicular to each other, defining a plane perpendicular to the axis YY' of pivoting of the grinding wheel support 4.
• the movements of the supports 3, 4 of the machine 1 consist of a pivoting movement of the wheel support 4 around the axis YY ', and of two translational movements of the support 3 of lens along axes XX 'and ZZ'.
• the pivot axis YY ' is vertical
• the grinding wheel support 4 When the grinding wheel support 4 is pivoted around the pivoting axis YY ', the grinding wheel also pivots about this axis (FIG. 1) while keeping the pivoting axis YY' tangent to the edge of the angular circular section 42.
• the lens support 3 and the rotating wheel support 4 are therefore mounted mobile on the frame 2, and the machine comprises means 11, 12, 13, 14, 100, 108, 109, 110 which make it possible to carry out movements of these supports ' 3, 4 relative to each other.
• These movements therefore consist of at least one pivoting movement along an axis YY 'of pivoting and movements ⁇ ⁇ h translation along two axes XX', ZZ 'of translation which define a plane perpendicular to the axis YY' of pivoting , these movements being the movements necessary for the generation of toric surfaces.
• the means making it possible to carry out the movements of the supports 3, 4 comprise means 12 making it possible to carry out a pivoting movement of the support 4 of the grinding wheel with respect to the frame 2 around the vertical pivot axis YY 'which is tangent to the circle defined by the angular circular cutting edge 42 of the grinding wheel 5, as well as means 11, 13 making it possible to carry out translational movements of the lens support 3 relative to the frame 2 along the axes XX ', ZZ' of translation which are perpendicular to each other and orthogonal to the axis YY 'of pivoting of the grinding wheel support 4, the lens being mounted on the lens support 3 with its thickness oriented along one of the axes of ZZ' translation - in particular with the axis ZZ 'passing through its geometric center and / or at least substantially parallel or coincident with the optical axis of the opposite surface of the lens in contact with the lens support 3 -.
• one ZZ 'of the translation axes is generally oriented along the thickness of the lens while the other XX' translation axis is generally oriented along the width of the lens.
• the glass blocks to be machined generally have a circular peripheral contour and the geometric center is then the center of the circle formed by this contour.
• one of the faces of the lens is generally machined beforehand according to a standard convex surface at high speed, the optical characteristics of the lens being defined by the concave surface machined on a machine according to the invention.
• the axis ZZ 'of translation is not always strictly coincident with the optical axis of the surface to be machined in the case where this surface is offset or prismatic with respect to the opposite surface in contact with the lens support 3.
• the axis ZZ ' of translation is generally normal to the surfaces of the lens and generally centered with respect to the lens while the other XX ′ axis of translation is generally parallel to the tangents to the surfaces of the lenses.
• These axes - and these movements necessary for the generation of toric surfaces are already known in themselves, for example from EP-A-0 176 894. It should be noted that if the above-mentioned embodiments are preferred, others variant embodiments of these movements are possible with respect to the frame 2, provided that the movements of the supports 3, 4 with respect to each other are carried out in an equivalent manner.
• the machine according to the invention incorporates possibilities of additional movements which make it possible in fact to generate all the usual usual forms of surfaces on a mineral glass lens.
• the invention is based on the fact that, surprisingly, it is possible to obtain all the usual forms of lens surface from the necessary movements of the generation of the toric surfaces by adding additional simple movements.
• abrasive wheels 5 in the form of a crown, the effectiveness of which has been demonstrated for machining mineral glass, not only for generating toric surfaces, but also for producing prismatic, off-center, aspherical, parabolic lenses, etc.
• the machine according to the invention thus comprises means 100 and / or 108 of vertical translation making it possible to carry out a movement in translation of the supports 3, 4 of lens and grinding wheel relative to each other along an axis Yl, YY '' parallel or coincident with the axis YY 'of pivoting of these supports 3, 4, one relative to the other, which is in the embodiments shown, the axis YY' of pivoting support 4 of grinding wheel relative to the frame 2.
• means 100, 108 for "vertical" translation for simplicity with reference to the generally vertical position of the axis YY 'of pivoting of the grinding wheel support.4 with respect to the frame 2, but l
• the invention also relates to all the other cases where the axis YY 'of pivoting is not vertical.
• the vertical translation means are means 100 making it possible to carry out a movement in translation of the lens support 3 relative to the frame 2 along an axis Yl which is parallel to the vertical axis YY 'of pivoting of the grinding wheel support 4 relative to the frame 2.
• the means of vertical translation are means 108 making it possible to carry out a movement in translation of the wheel support 4 with respect to the frame along the axis YY ′ of pivoting of the wheel support 4 with respect to the frame 2.
• the pivot axis YY ' is therefore, according to the invention, also a translation axis, even if it remains designated for simplicity "pivot axis YY' throughout this text, with reference to the pivoting movement which is always intended to generate a toric surface.
• the translation along the pivot axis YY ' makes it possible to shift vertically, that is to say in the direction of this axis YY', the lens support 3 relative to the wheel support 4.
• these two supports 3, 4 can also be offset relative to each other in the horizontal direction XX ′, it can be seen that it is possible to offset the origin and the axis in any angular direction optics of the surface generated on the lens with respect to the geometric center of this lens, or with respect to the optical axis of the opposite face, possibly already machined of the lens. In this way, it is possible to produce a surface which is offset from the lens.
• the off-center is equivalent to the realization of a prismatic surface.
• any prismatic surface by modifying, by calculation, the machining dimensions along the axis ZZ ', and this possibly as a function of the vertical off-center produced along the axis YY'.
• the machine includes means 108, 109, 110 for tilting the axis 6 of proper rotation of the grinding wheel 5 relative to the horizontal plane defined by the axes XX ', ZZ' of translation.
• This inclination which can be given to the grinding wheel support 4 and to the axis 6 of the grinding wheel's own rotation defines the value of the vertical component of the prism.
• this inclination is obtained (FIGS. 6b and 6c) by the means 108 of vertical translation and by means 109 of horizontal pivoting of the support 4 of the grinding wheel relative to the frame 2 around an axis X3 perpendicular to the axis 6 of proper rotation of the grinding wheel 5 and orthogonal to the axis YY 'of pivoting.
• the combination of vertical translation and horizontal pivoting around the axis X3 makes it possible to obtain a pivoting of the wheel support 4 around an axis X2 perpendicular to the vertical axes YY 'of pivoting of the wheel support 4 and 6 of proper rotation of the grinding wheel 5 and passing through the cutting edge 42 of the grinding wheel 5.
• these means 108, 109, 110 of inclination can be produced by means (not shown) for pivoting the grinding wheel support 4 directly around the axis X2 and / or by means 110 for pivoting the lens support 3 around the axis XX 'of translation (FIG. 6c).
• the vertical axis YY ′ of pivoting of the grinding wheel support 4 with respect to the frame 2 remains in its vertical position when the inclination of the axis 6 of rotation of the grinding wheel 5 is achieved.
• the machine according to the invention further comprises means 14 for axial pivoting enabling movement to be carried out pivoting of the supports 3, 4 relative to each other about the axis ZZ 'of translation which passes through the geometric center of the lens and / or which is at least substantially parallel or coincident with the axis d optics of the opposite surface of the lens.
• the means 14 for axial pivoting are means 14 making it possible to carry out a pivoting movement of the lens support 3 and / or of the grinding wheel support 4 relative to the frame 2 around the axis ZZ 'of translation.
• it is the lens support 3 which is movable relative to the frame 2 and which pivots around " the axis ZZ 'of translation.
• axis ZZ 'of translation is, according to the invention, also a pivot axis but remains designated for simplicity "axis ZZ' of translation" throughout this text.
• the means 11, 12, 13, 14, 100, 108, 109, 110 making it possible to carry out the movements of the supports 3, 4 comprise motor means which produce and control the movements of translation and / or pivoting of these supports 3, 4 relative to the frame 2 along the axes of translation and / or pivoting.
• the machine according to the invention also comprises means 15, 16, 17, 18 programmable motor control means which are capable of being active during the machining of the surface of the lens.
• These programmable control means include:
• means 15 for inputting and means 16 for memorizing parameters defining the desired theoretical shape of the surface to be ground, means 17 for calculating the characteristics of different electrical control signals for the motor means as a function of the theoretical shape of the surface to be ground,
• each motor means controlled by the programmable control means comprises a movable member 19, 20, 21, 22, 102 driven in movement and control means 23, 24, 25, 26, 103 in closed loop of the position of the movable member 19, 20, 21, 22, 102 and in that the calculation means 17 are programmed to determine the characteristics of the control signals by interpolating the speeds and accelerations between the different movements along the axes XX ', YY', Yl, ZZ ', the emission means 18 transmitting the signals electrical controls according to a chronology defined by the calculation means 17.
• the programmable control means 15, 16, 17, 18 generate movements of the means 11, 12, 13, 14, 100 motors such that the angular circular cutting edge 42 comes into contact with the lens in a portion 43 of the circle defined by the trace of this edge 42 in rotation about the own axis of rotation 6, and this contact portion 43 is diametrically opposite to the pivot axis YY 'of the support 4 of the grinding wheel.
• This means that contact between the grinding wheel 5 and the lens is always diametrically opposite side of the grinding wheel 5 relative to the axis YY 'of pivoting of the grinding wheel support 4.
• the means 11, 12, 13, 14, 100 motors controlled by the programmable control means 15, 16, 17, 18 all consist essentially of at least one hydraulic servo-amplifier device incorporating:
• a hydraulic actuating element 27, 28, 29, 30, 101 such as a jack comprising a movable member 19,
• an electric stepper motor 31, 32, 33, 34, 104 controlling the actuating element 27, 28, 29, 30, 101 by means of a valve 35, 36, 37, 38, 105 controlled by the electric stepper motor 31, 32, 33, 34, 104.
• Such a hydraulic servo-amplifier device 11, 12, 13, 14, 100 is known per se and can consist, for example, of a linear amplifier as described in European patent application EP-A 0 336 887.
• the precision of the position of the movable member 19, 20, 21, 22, 102, and its reliability, i.e. the stability of the precision and its repeatability can be of the order of a hundredth of a millimeter or less.
• the programmable means 15, 16, 17, 18 for controlling the motor means control the operation motor means and therefore the movements of the supports 3, 4 during each grinding pass.
• the motor means drive at least one of the two supports 3, 4 in movement relative to the frame along at least one axis XX ', YY', Yl, ZZ 'of translation and / or pivoting during each pass of grinding
• the programmable control means determine the characteristics of the control signals for such an axis of translation and / or pivoting of a support 3, 4 as a function of the path which must be traversed by the support 3, 4, calculation means 17 performing an interpolation of the speeds and accelerations of the different movements along the different axes of pivoting or translation.
• the means 11, 12, 13, 14, 100 motors drive both the lens support 3 and the wheel support 4 in movement during each grinding pass under the control of the means 15, 16, 17 , 18 programmable controls.
• the means 11, 12, 13, 14, 100 motors drive the supports 3, 4 in movement under the control of the means 15, 16, 17, 18 programmable controls according to all the axes of movement of these supports during each grinding pass.
• the programmable control means send the control signals to the motor means and effectively control the position and the speed of each of the supports 3, 4 in each of these translational movements or pivot.
• the movements determined by the calculation means of one of the supports along one or more of these axes of translation and / or pivoting are zero for such and such a form of surface to be generated.
• the movements of the supports 3, 4 can be arbitrary and are determined and controlled by the programmable control means - in particular the calculation means 17 - as a function of each surface to be generated.
• the movements of the supports 3, 4 can therefore vary almost infinitely and in ranges of continuous values in amplitude, speed and acceleration.
• the machine 1 comprises a block 39 incorporating a programmable automaton consisting of input means 15, storage means 16, calculation means 17, and means 18 for transmitting control signals.
• the block 39 constitutes a physically separate entity from the other components of the machine 1 and is removable. It also makes it possible to supply the machine with electrical power.
• Block 39 incorporates the various electronic cards making it possible to produce the programmable control means in practice.
• the input means 15 may consist of a control console 15 comprising a keyboard 40 and a display screen 41.
• the storage means 16 and the calculation means 17 may consist of a microcomputer such as an IBM PC (registered trademark). This microcomputer is programmed to perform the various calculations and interpolations necessary for the operation of the machine 1 according to the invention. For example, one can use the SELEDATA (registered trademark) system MPS 50 sold by the company REGUELEC (Paris, France). Such a system is programmable and incorporates the storage means, the calculation means and the means for transmitting control signals.
• the machine 1 (shown in FIGS. 1 and 2) comprises a hydraulic servo-amplifier device 12 for generating the pivoting movement of the grinding wheel support 4 around the pivot axis YY ', a hydraulic servo-amplifier device 13 for generating the translational movement along the axis ZZ 'of translation of the lens support 3, a hydraulic servo-amplifier device there to generate the translation movement along the axis XX' of translation of the lens support 3 and a servo-amplifier device hydraulic 100 to generate the translational movement of the lens support 3 along the axis Yl parallel to the axis YY 'of pivoting of the wheel support 4.
• the pivoting of the grinding wheel support 4 around the axis YY ' also takes place in such a way that the grinding wheel 5 comes opposite the lens support 3 and the lens associated with it so that its circular cutting edge 42 comes on contact with the lens.
• FIGS. 1 and 2 the position of the lens supports 3 and 4 of the grinding wheel supports is shown in solid lines when all the drive means are at a reference position defining a geometric origin for the machine 1.
• dashed dashed lines we have shown the lens holder 3 and the wheel holder 4 partially in extreme positions.
• a plate 44 is mounted integral with the movable member 21 of the hydraulic servo-amplifier 13 generating the translational movement of the lens support 3 according to the axis ZZ 'coincides with the optical axis of the opposite surface of the lens.
• On this plate 44 is mounted a second plate 45 to which the second hydraulic servo-amplifier 11 is rigidly associated perpendicularly to the first hydraulic servo-amplifier 13.
• the movable member 19 of the hydraulic servo-amplifier 11 which generates the movement of the support 3 of lens along the axis XX 'is rigidly associated with a shaft 46 which is itself rigidly associated with the lens support 3 mounted on a slide 47 parallel to the axis XX' and integral with the plate 44.
• the hydraulic servo-amplifier 13 generating the translational movement of the support 3 of the lens along the axis ZZ ' is itself mounted on a plate 107 movable in vertical translation relative to the frame 2 by means of slides.
• the servo amplifier 100 performing the vertical translation along the axis Yl has its movable member 102 associated with this plate 107 and its body 101 rigidly associated with the frame 2, or in a variant not shown on the support of the grinding wheel.
• the grinding wheel support 4 is pivotally mounted around the axis YY 'thanks to a vertical shaft 48 mounted free in rotation relative to the frame 2 around the axis YY', and with which is associated a plate 49 supporting the rotary shaft 9 of the wheel 5, the motor 7, and the support 4 of the wheel.
• the motor assembly 7, rotary shaft 9, and wheel support 4 is mounted on the plate 49 by means of a micrometric adjustment slide 50 which allows, by the action on a crank 51, to adjust in advance the position of the support 4 of the grinding wheel and of the grinding wheel 5 relative to the axis YY '.
• the plate 49 supporting the motor 7, the rotary shaft 9 and the grinding wheel support 4 can also be mounted on a second slide 56 perpendicular to the axis 6 of the grinding wheel's own rotation and actuated manually by a crank 57.
• a crank 57 With the cranks 51 and 57, one can manually place the axis YY 'tangent to the angular cutting edge 42 of the grinding wheel 5 after its assembly. To do this, it suffices to know in fact the diameter of the grinding wheel 5.
• the adjustment slides 50, 56 as well as the cranks 51, 57 can be omitted when using an automatic detection and adjustment device mounted on the support. 3 of front lens and in place of the lens. The detection device then acts in effect on the origin of the axes of movement in pivoting and / or in translation, after the calculation means 17 have calculated the possible correction to be made.
• the lens is positioned relative to the support 3 of the lens along an optical axis coincident with the axis ZZ 'automatically.
• Numerous types of lens support 3 are already known which make it possible to place the lens correctly and perfectly centered with respect to the axis ZZ ′ of the support 3 of the lens.
• lens supports 3 are known which make it possible to center the optical axis of this face relative to the axis ZZ 'of the support 3 of the lens.
• the hydraulic servo-amplifier 12 generating the pivoting of the grinding wheel support 4 can be, like the other hydraulic servo-amplifiers 11, 13 allowing the translational movements of the lens support 3, produced in linear form. That is to say that the movable member 20 of this hydraulic servo-amplifier 12 moves in translation, and its translational movement is transformed into rotation at the level of the pivot shaft 48.
• the movable member 20 is for example connected to a pinion 52 mounted to rotate freely relative to the frame 2, and this pinion 52 is itself connected by a chain or a belt 53 to a second pinion 54 integral with the pivot shaft 48 around the axis YY '.
• the machine 1 according to the invention also comprises means 55 for producing pressurized fluid for the various hydraulic motor means 11, 12, 13, 14, 100.
• the machine shown in FIGS. 1 and 2 also comprises a hydraulic servo-amplifier device 14 for pivoting the lens support 3 around the axis ZZ 'of translation coincident with the optical axis of the opposite surface of the lens to generate.
• the hydraulic servo amplifier 14 allowing this pivoting is connected to the shaft 46 secured to the lens support 3 so that the movement of its movable member 22 causes this shaft 46 to rotate about the axis ZZ '.
• This pivoting can be used for example to achieve a 180 ° reversal of the lens during a grinding pass by performing the grinding in the opposite direction relative to the lens.
• a movement known as a "back-cut” is known in itself and used in particular when the thickness of the edges of the lens is small.
• the pivoting of the lens support 3 around the axis ZZ ' makes it possible to generate any surface symmetrical with respect to this axis ZZ', that is to say surfaces which are not necessarily toric, such as ellipsoid or paraboloid surfaces of revolution .
• the machine according to the invention makes it possible, from a block of glass whose convex face is previously machined, to generate a prescription lens whose characteristics are arbitrary as well as regards the optical characteristics as the profile of the lens adapted to the frame.
• the pivoting of the lens support 3 around the axis ZZ 'of translation also makes it possible to bevel the peripheral edges of the face of the lens which has just been generated on the machine. This avoids a step generally performed manually before polishing, which allows, in addition to the savings in labor cost, to automatically transfer the lens at the outlet of the machine according to the invention to a polishing machine.
• the machine according to the invention makes it possible, from lens blocks with a pre-machined convex face, to perform all the machining steps on this block in full to form the prescription lens and which are necessary before polishing. And in doing so, we can machine any form of prismatic, off-center, aspherical or toric surface.
• the corresponding motor means 14 is consisting of a rotary hydraulic servo amplifier 14 or of a stepping motor connected by a gear to the shaft 46 secured to the support 3 of the lens.
• a machine 1 according to the invention has an extremely low number of mechanical and hydromechanical components, and that these components are simple and inexpensive. In particular, no position sensor or detector is used.
• the machine 1 according to the invention does not require any open loop regulation. Interpolation of speeds and accelerations also avoids the need for regulation of speeds and accelerations by an automatic control.
• the programmable control means return all the motor means to their reference position defining a geometric origin for the machine 1 before each grinding pass, and the calculation means 17 determine the characteristics of the electric control signals to generate the movements of the supports 3, 4 from this geometric origin.
• the geometric origin is determined by mechanical stops of the motor means 11, 12, 13, 14, 100, and for example by the mechanical end-of-travel stops of the hydraulic servo-amplifier devices used. Because of this reset to zero of all movements, that is to say the reset to the geometric origin of the machine before each grinding pass, any possible error that would have occurred during a previous pass. is canceled automatically and not accumulated on subsequent passes.
• the calculation means 17 perform a linear polygonal interpolation of the speeds of the different translational or rotational movements of the supports 3, 4 during each grinding pass.
• the complex trajectories of the movable members 19, 20, 21, 102 that is to say the trajectories which are curved, are treated as polygons.
• Each trajectory is broken down into straight line segments, the speed being constant over each segment.
• the SELEDATA (registered trademark) MPS 50 positioning system mentioned above allows such polygonal interpolation.
• the calculation means 17 are programmed to calculate the difference between the desired theoretical shape of the surface to be generated and the shape generated during grinding.
• the calculation means 17 carry out the calculation, from programmed formulas, and before each grinding, of a plurality of theoretical points defining the desired theoretical shape of the toric surface as a function of the stored parameters defined and entered " by the user.
• the calculation means 17 also calculate the geometric characteristics of the grinding (amplitude and speed of the movements of the supports 3, 4) according to the stored parameters. calculating a plurality of generated points defining the surface during grinding.
• the calculation means 17 determine the difference which exists between the theoretical and generated points corresponding two by two.
• the calculation means 17 compare this calculated difference with an admissible threshold value. If the deviation of a pair of theoretical and generated points is less than the threshold value, the calculation means 17 perform the interpolation of the speeds and supply the necessary instructions to the transmission means 18 which emit the electrical control signals . In the case where the difference between at least a pair of theoretical and generated points is less than the threshold value, after the emission of the control signals and the grinding, the calculation means 17 effect a modification of the grinding characteristics having for the purpose of eliminating or minimizing this difference, then proceed to resetting the geometric origin of the supports 3, 4 and resume the calculations in the step of calculating the plurality of points generated.
• Figure 4 illustrates the different steps of such a process.
• Step 59 corresponds to the initial reset to the geometric origin of the machine 1, all the drive means being placed in their reference position in abutment.
• Step 60 corresponds to the calculation of the theoretical shape of the surface to be generated from the parameters entered and stored. In the case for example of a toric surface, these parameters are in practice the radius of the base curve and the radius of the cylinder curve or the diopters characterizing these two curves. From these radii or these diopters, it is known how to calculate the theoretical shape of the surface, and in particular the coordinates x, y, z with respect to the axes XX ', YY', ZZ 'represented in the figures.
• the parameters also include the x, y coordinates of the offset along the axes XX 'and YY'.
• the parameters include the offset previously brought along the axes XX 'and Yl or YY' to define the orientation of the prism and the progressive offset (in diopters) along the axis ZZ 'to define the value of the prism.
• FIG. 4 illustrates the calculation method carried out by the calculation means 17.
• Step 61 corresponds to the calculation of the grinding characteristics, namely the rotational movements around the axis YY 'of the wheel support 4 and translation along the axes XX' and ZZ '.
• Many known formulas can be used in this regard. For example, it is possible to give a fixed pivot angle to the wheel support 4 and generate only the translational movements along the axes XX 'and ZZ'.
• French patent 2,204,987 gives an example of possible movement formulas. These formulas for calculating the characteristics of the different inclinations and movements during grinding are known to those skilled in the art.
• Step 62 consists in calculating the shape generated in practice. This calculation is carried out by software according to a known formula determining the equations of the surface generated by the rotation of an inclined circle, taking into account the offset and / or the inclination of the axis 6 and / or the offset according to ZZ '.
• Step 63 consists in calculating the difference between theoretical and generated points two by two. In 64, all the deviations calculated by step 63 are compared with respect to a maximum threshold value. If this maximum threshold value is not reached, interpolation 65 is carried out and the calculation means 17 supply the instructions at 66 to the transmission means 18.
• the same interpolation 65 and the same supply 66 to the transmission means 18 are carried out, but a modification of the grinding characteristics is made at 67, a reset to the geometric origin of the machine in 68 and the process is repeated in step 62 of calculation where the grinding characteristics of the subsequent pass are modified.
• the modification of the grinding characteristics is carried out to grind the lens at the point where the deviation is greatest.
• FIG. 6a illustrates the kinematics of the machine shown in FIGS. 1 to 3.
• the motor 7 rotates the grinding wheel 5 around its own axis 6 of rotation relative to the grinding wheel support 4 which, itself is mounted pivoting around the vertical axis YY 'with respect to the frame 2, thanks to a motor device 12.
• the axis YY' is fixed relative to the frame and the grinding wheel 5 pivots about this axis which is tangent to its cutting edge circular 42.
• the lens 70 is mounted on the lens support 3 which is pivotable about the axis ZZ 'passing through the geometric center of the lens 70.
• a motor device 14 generates the pivoting movement of the support 3. Furthermore, the motor devices it and 13 make it possible to generate the translational movements in the axes XX 'and ZZ' respectively. And, the motor device 100 associated with the frame 2 makes it possible to generate the vertical offset by translation of the assembly along the axis Yl parallel to the axis YY 'of pivoting of the grinding wheel support 4.
• the motor devices shown with a circular arrow are those which have the function of generating a rotary pivoting movement.
• these motor devices can be produced from either linear devices and a mechanism for transforming linear movement into rotary movement, or directly from rotary motor device.
• the devices represented with a sign composed of two opposite arrows are those which have the function of generating a translational movement.
• the wheel support 4 comprises means 108, 109 for vertical offset consisting of a motor device 108 for vertical offset in translation along the axis YY 'and of a device 109 d 'inclination of the axis 6 of proper rotation of the grinding wheel relative to the plane defined by the axes XX', ZZ ', that is to say also relative to the axis YY' which is fixed relative to the frame .
• the drive device 109 pivots the grinding wheel support 4 around an axis X3 parallel to the axis to the axis XX '.
• the variant shown in FIG. 6c combines the vertical translation means 100 of the lens support 3 relative to the frame 2, the vertical translation means 108 of the wheel support 4 relative to the frame 2 and the tilting means 109 of the 'own axis of rotation 6 of the grinding wheel with respect to the plane of the axes XX', ZZ ', that is to say with respect to the axis YY'. These means are produced by the motor devices 100, 108, 109.
• a motor device 100 allows a pivoting movement of the lens support 3 relative to the axis XX ', so as to tilt the axis 6 proper rotation of the grinding wheel 5 relative to the plane defined by the axes XX 'and ZZ' not by a movement of the grinding wheel support 4 relative to the frame only, but also by a movement of the lens support 3 relative to the frame 2.
• a person skilled in the art can easily make machines corresponding to the kinematic diagram of FIGS. 6a, 6b, 6c, the conventions of representation of which are known to him. Obviously, other variants not shown of the invention are possible, the examples of Figures 6a, 6b, 6c were given only without limitation.
• a machine therefore comprises means 15, 16, 17, 18 for controlling the means 11, 12, 13, 14, 100 slave motors corresponding to the movement capable of being active during grinding.
• the machine comprises at least means for controlling the means 11, 13 motors corresponding to the translational movement along the axes XX ', ZZ' of the lens support 3 relative to the frame 2, as well as means for shifting vertical of the wheel support 4 relative to the frame 2.
• These vertical offset means are means of vertical translation along the axis YY 'and / or means of tilting the axis 6 of the wheel's own rotation relative to in the plane of the axes of translation XX ′, ZZ ′ of the support 3 of the grinding wheel relative to the frame 2.
• a machine according to the invention therefore makes it possible to implement a method according to the invention for generating by grinding any surface - in particular off-center and / or prismatic - of optico-ophthalmic lens made of organic or mineral glass using a grinding wheel 5, the abrasive part 106 of which is generally in the form of a rotating crown to define a circular cutting edge 42 and which is rotatably mounted on a grinding wheel support 4 around an axis 6 of rotation, process in which the support 4 is moved grinding wheel and the lens support 3 relative to each other in at least pivoting movements along an axis YY 'of pivoting and in translation along two axes XX', ZZ 'of translation which define a plane perpendicular to the axis YY ', the axis 6 of rotation of the grinding wheel being orthogonal to the axis YY' of pivoting.
• the axis 6 of the proper rotation of the grinding wheel 5 is offset relative to the plane defined by the axes XX ′, ZZ ′ of translation.
• the lens and grinding wheel supports 3, 4 are displaced relative to each other, in translation along said pivot axis YY '. More particularly, according to the invention, the supports 3, 4, of lens and grinding wheel are moved prior to grinding by shifting these supports 3, 4 by a predetermined distance in the direction of the pivot axis YY ', this distance offset remaining constant and fixed during the grinding of the surface to be generated.
• the motor means 100 realizing the offset along the axis Yl parallel to the axis YY ' also include means 103 for closed-loop control.
• the axis 6 of the proper rotation of the grinding wheel 5 is inclined relative to the plane of the axes XX ', ZZ' of translation.
• This own axis of rotation 6 can be inclined before grinding by a predetermined angle remaining constant during grinding, and / or control changes in inclination during grinding.
• the means 108, 109, 100 motors generating this tilt comprise closed-loop control means.
• the method according to the invention is also characterized in that the supports 3, 4 of lens and grinding wheel are moved one with respect to the other, in pivoting around at least one ZZ 'of the axes XX', ZZ 'of translation - in particular around the axis ZZ' passing through the geometric center of the lens and / or at least substantially parallel or coincident with the optical axis of the surface previously generated on the opposite face of the lens -.
• the lens and wheel supports 3, 4 are moved in pivoting around the axis ZZ ′ before and / or after grinding the surface to machine the peripheral edges of the lens.
• this pivoting around the axis ZZ ′ is used before the generation of the surface to carry out the trimming and after the generation of the surface to carry out the peripheral bevelling.
• This movement is also used during the grinding of the generation of the surface when this surface is neither toric nor spherical and is any surface of revolution around the axis ZZ ', as well as to carry out the reversal of 180 ° possibly.
• this possibility of pivoting movement around the axis ZZ ' can be used to adjust the angular position of the lens before machining relative to this axis ZZ', and therefore the angular offset of the more powerful meridians of the two faces of the lens around the axis ZZ '.
• the lenses are locked on their support 3 always in the same position and the machine according to the invention calculates and performs the initial offset movements necessary for the machining of the surface to be machined which may be any. The initial manual settings are therefore deleted and the machining possibilities increased.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)

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Citations (4)

• 1992
  • 1992-02-26 FR FR9202233A patent/FR2687598A1/fr active Granted
• 1993
  • 1993-02-26 WO PCT/FR1993/000199 patent/WO1993016842A1/fr active Application Filing

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