Method and apparatus for the application of a protective film to one face of a series of ophthalmic lenses

The present invention relates to a method and apparatus for bonding a protective film on one side of a series of ophthalmic lenses according to the preambles of claims 1 and 6.

In the field of manufacturing ophthalmic lenses, it is often necessary to apply an adhesive film on the surface of a lens to protect it against scratches or against attack by foreign bodies, for example during a so-called "blocking" or "holding device" of a lens (step of securing a metal block on one face of the lens by casting a low melting point metal, for the subsequent fitting of the lens on the lens holder of a planing machine, a trimming machine or machine polishing ophthalmic lenses). The application of such a protective adhesive film is particularly recommended in the case of lenses made of an organic material, but it can also be performed in the case of glass lenses.

To apply the adhesive film on one side of a lens, it is known from US-A 4,242,162, on which are based the preambles of claims 1 and 6, of placing the lens in a cavity open upwards, on a support vertically movable in the cavity under the action of a jack. An adhesive tape is then manually moved over the cavity in which the lens is located, and closes it. An annular jaw is then manually moved and just dumped the tape and hold it against the edge of the opening of the cavity. The lens holder is then moved vertically upwards by means of the jack, which has the effect of applying the tape against the upper face of the lens, possibly with the help of vacuum where the cavity is connected to a pump vacuum. The tape is then manually cut by the operator around the lens using a kind of cutting tool "cutter". The jaw is then manually opened and the lens removed manually with the adhesive film bonded washer on its upper face. All or almost all susindiquées operations were therefore done manually, therefore at a relatively slow rate. In addition, since the adhesive tape is initially flat and the side to protect the lens usually has a curved surface, it generally can not avoid the formation of wrinkles during application of the tape on the face of the lens , particularly where the face of the lens has a strong curvature (that is to say a small radius of curvature). Such folds are detrimental to good adhesion of the adhesive tape on the face of the lens and obtain a layer of uniform thickness between the lens and the metal block which is subsequently cast onto the adhesive film.

The present invention therefore aims to provide a method and a device for adhering a protective film on one side of a series of ophthalmic lenses with a significantly higher rate than with the previously known technique.

Alternatively, the present invention also aims to provide an apparatus of the type above indicated in which the protective film is applied on the face of the lens, without the formation of folds, even if said face has a smaller radius of curvature.

Alternatively, the invention also aims to provide an apparatus of the above indicated type, capable of applying the protective film on the entire face of the lens to be protected, irrespective of the diameter of said lens.

The method of the present invention for adhering a protective film on one side of a series of ophthalmic lenses comprises the steps of placing a lens of said lens array on a support, unwinding a roll of composite tape formed of an adhesive tape having an adhesive face, and a strippable tape covering said adhesive face, to be separated from the peelable ribbon tape to permit application of adhesive tape to a face of the lens placed on said support, and is characterized in that it further comprises the operations consitant punching a hole of predetermined diameter, larger than that of the lens, in the separate peelable ribbon tape, to consolidate the punched peelable tape and the adhesive tape in such a way that a round portion of the adhesive side of the tape remains exposed through the hole punched peelable tape, passing the peelable tape and punched tape between said support and a support pad, applying said exposed portion of the adhesive side of the adhesive tape to a face of the lens placed on the support, by relative movement of at least one of said support and said buffer towards each other, cutting the tape around the peripheral edge of the lens to evacuate the lens with the cutout portion of adhesive tape adhered to the face of said lens and forming said protective film, to remove the remaining cut part of the tape and the peel tape punched, and repeating the preceding operations for each lens said series.

Preferably, during the tape application operation on a face of a lens, the peelable tape is punched in preparation for the tape applying operation on a surface of the next lens of the said series of lenses . In addition, during application of the tape operation on a face of a lens and the cutting operation of the adhesive tape, the composite tape is preferably squeezed between two jaws comprising aligned circular holes having an inner diameter corresponding the diameter of the hole punched in the peel-off tape.

The apparatus for carrying out the method of the present invention is characterized in that it further comprises a first set of guide rollers to guide the composite strip along a predetermined path, a second set of guide rollers for guiding the peelable tape of the composite tape according to a looped path that extends away from said predetermined path and returns to blend therewith, a punching device on the looped path to punch the peel-off tape, a lens holder located on one side of said predetermined path of the composite tape, on the side of the peelable tape, downstream of said looped path, a backup pad located on the other side of said predetermined path in the alignment of the lens holder, the at least one of said lens holder and said backup pad being movably mounted perpendicular to said predetermined path, at least one actuating means connected to one of said lens support and said buffer for pressing together the composite tape, a device of cutter on the predetermined path of the composite tape downstream of said looped path, and a drive means acting on the composite tape to move along said predetermined path.

Preferably the punching device comprises a punch and a matrix which have a diameter larger than the largest existing diameter of ophthalmic lenses. Preferably, the cutting device comprises a support mounted for rotation about an axis which is perpendicular to the predetermined path of the composite tape, two cutting blades which are mounted on said carrier and extend parallel to said axis equidistant from celui- thereof, and a motor coupled to said support to rotate with two cutting blades about said axis. Advantageously, the two cutting blades are adjustable in spacing from the axis of rotation of the cutting device.

Other features and advantages of the present invention will emerge more clearly during the following description, given by way of example with reference to the accompanying drawings in which:<ul><li>Figure 1 is a part side elevation and partly in vertical section, showing one embodiment of the apparatus of the present invention.</li><li>Figure 2 is a sectional view showing, on a larger scale, the punching device of the apparatus of Figure 1.</li><li>Figure 3 is a part side elevation and partly in vertical section showing, on a scale grtande, other active elements of the apparatus of Figure 1.</li></ul>

The apparatus of Figure 1 which may form part of a preparation machine and "blocking" or "A blocking" ophthalmic lenses, comprises an unwinding roller 1 and a coil winding 2, which are rotatably mounted in a frame 3. the reel spool 2 can be rotated by a motor 4, for example an electric motor whose output shaft 5 is connected to the drive shaft 6 in the spool 2 by a suitable transmission 7, by eg a chain drive.

The unwinding roller 1 carries a roll 8 of a composite tape 9 formed of an adhesive tape 9a and 9b with a peelable tape covering the adhesive face of the tape 9a. The composite ribbon 9, which is unwound from the roller 8, first of all passes over a first table 11, then over a guide roller 12 at whose output the peelable tape 9b is separated from the tape 9a. Then, the peelable tape 9b follows a looped path passing successively around the two guide rollers 13 and 14, and the two ribbons 9a and 9b are combined together by passing between a pair of rollers 15 and 16. Then, the composite tape 9 passes over a second table 17, a short distance from the upper face thereof, and then around a guide roll 19, to be finally rewound onto the reel spool 2. the composite tape 9 may be for example consisting of a tape marketed by the company "3M" under the reference "1641".

The apparatus of Figure 1 further comprises a punching device 21 (shown in greater detail in Figure 2), which is installed on the loop path followed by the tape peel 9b, between the guide rollers 13 and 14. preferably, the punch 22 and the die 23 of the punching device 21 respectively have an outer diameter and an inner diameter which is slightly larger than the largest existing diameter of ophthalmic lenses. For example, the diameter of the punch 22 and die 23 may be between 85 and 90mm. For its actuation, the punch 22 is connected to the piston rod 24a of an actuator 24, for example a pneumatic cylinder. Each time the punch 22 is operated, the washer cut by the latter in the strip 9b is ejected by blowing compressed air through a hole 25 drilled in the center of the end face of the punch 22. The hole 25 communicates with a passage 26, which is drilled radially into the punch 22 and which, when the latter occupies the position shown in the left part of Figure 2, in turn communicates with a passage 27 drilled radially into the 23 matrix and connected by a connection 28 and by a pipe (not shown) to a compressed air source (also not shown).

The Figure 1 apparatus further comprises a lens holder 29, a backup pad 31 and a cutting device 32. The support 29 on which can be placed a lens L, one of the two faces, for example the convex surface, should be covered with a protective film, is located beneath a circular hole 34 (best seen in Figure 3) of the table 17. the hole 34 has a diameter equal or slightly larger the diameter of holes formed by the punching device 21 in the tape 9b. The lens L can be held on the support 29 for example by means of a not shown suction device. The backup pad 31 is located above the composite tape 9 and the hole 34_: The support 29 or pad 31, preferably both can be moved towards each other as discussed below, to apply the composite adhesive tape 9a tape 9 on the exposed face of the lens L carried by the support 29.

As is more particularly visible in Figure 3, 17a area of ​​the table 17, which borders the hole 34 is slightly raised relative to the plane upper face of said table, so as to form a fixed jaw adapted to cooperate with a movable jaw 35 to clamp the composite tape during the tape application operation 9a on the exposed face of the lens L and during the cutting of the tape operation (operations that will be described later). The movable jaw 35 has a circular hole 36 which has an inner diameter equal to or slightly larger than that of the hole 34 and which is axially aligned therewith. The movable jaw 35 extends between and is secured to two parallel arms 37, of which only one is visible in the drawings and which are pivotally mounted, at one end, about an axis 38. At their other end, the arm 37 are hinged by a pin 39 at respective ends of the legs of a bracket 41 in form of U. the bottom part of the bracket 41 is secured to the cylinder 42 of a jack, for example a pneumatic cylinder, whose rod piston 43 is attached to the table 17. Thus, by actuating the cylinder 42,43, the movable jaw 35 may be freely moved away from the composite tape 9 to release it and allow its advance, and clamped against the fixed jaw 17a to pinch the tape 9.

A carriage 44 (Figure 1) is mounted movable relative to the table 17 in a direction parallel to the axis of the hole 34, as indicated by the double arrow F. The carriage 44 is connected to the piston rod 45 of a cylinder 46, for example a pneumatic cylinder, and can be moved between two limit positions defined respectively by means of adjustable stops 47 and 48. two detectors 49 and 51 are associated respectively with the abutments 47 and 48 and transmit a signal when the carriage 44 reaches the corresponding limit position.

At its lower end the support 29 is coupled to a shaft 52 which can be rotated by a predetermined angle, in both directions of rotation, by an actuating device 53 carried by the carriage 44. The actuating device 53 may for example, be constituted by a pinion which is fixed to the shaft 52 and which meshes with a rack connected to a cylinder, for example a pneumatic cylinder. Thus, the support 29 can be moved between a first position in which the carrier 29 and the lens L supported by the latter are aligned with the hole 34 of the table 37, and a second position in which the support 29 is laterally spaced from hole 34. the first and second positions of the carrier 29 may be defined by a projecting piece 54 which is fixed on a side of the support 29 and which is engageable with one or other of two stops (not shown ) fixed to the carriage 44. two sensors (only one sensor 55 is visible in Figure 1) are respectively associated with these last two stops and emits a signal when the carrier 29 is in the corresponding position.

When the carriage 44 is in the position defined by the stop 47 and the support 29 is in the second position (laterally spaced from the hole 34 of the table 17), the upper part of the carrier 29 appears in a window (not shown) provided in the frame of the apparatus. In this position the support 29, a lens L may be placed on the carrier 29 (optionally discharged from said support) manually or by means of an appropriate transfer device. When the support 29 is in its first position (aligned with the hole 34 of the table 17) and the carriage 44 is moved by the cylinder 46 in the position defined by the stop 48, the lens L previously positioned on the support 29 is pressed against the adhesive side of the tape 9a of the composite tape 9 through the hole 34 of the table 17.

The backup pad 31 is designed to fit the shape of the exposed surface of the lens L when it is pressed against the tape 9a and pushes it against the backup pad 31. While the buffer 31 can include an element of a compressible and elastically deformable material, it is preferably constituted by a tool such as that described in European patent application of the same applicant, filed March 11, 1988, under number 88 400577.8 entitled "tool autoconformable on the surface of an ophthalmic lens ". Briefly, as shown in Figure 3, the backup pad 31 includes a holder 56 having a cavity 57 open towards the table 17. Two elastically deformable membranes 58 and 59 are fixed by their peripheral edge to the side walls of the cavity 57 and define a space therebetween which is filled with an incompressible material, in small-sized grains, for example, beads 61 made of glass or steel having a diameter of about 1 mm. Thus, when the lens L and the tape 9a are pressed against the membrane 59, the assembly 58-61 deforms and conforms closely to the adjacent face of the lens L. The assembly 58-61 may then be temporarily rigidifé so to form a rigid support surface by performing vacuum in the space between the two membranes 58 and 59 through a lateral orifice of the support 56 connected by a coupling 62 and a pipe (not shown) to a source of vacuum (also not shown).

The support 56 of the backup pad 31 is connected to the lower end of the piston rod 63 of a jack, for example a pneumatic jack, whose cylinder 64 is fixed to a trolley 65. By actuating the cylinder 63, 64, the backup pad 31 may be discarded at will of the composite tape 9 and the table 17 and brought into contact with the movable jaw 35, adjacent the non-adhesive side of the tape 9a. The carriage 65 is movably mounted relative to the frame 3 and to the table 17, for example by means of a ball slide in a direction parallel to the table plane and the path followed by the tape 9.

The cutting device 32 is carried by a further carriage 66 which is movably mounted relative to the carriage 65, for example by means of a ball slide in a direction perpendicular to the table plane 17 and the path followed by the 9. ribbon carriage 66 is fixed cylinder 67 of a jack, for example a pneumatic cylinder, whose piston rod 68 is supported on the carriage 65. Thus, by actuating the cylinder 67,68, the carriage 66 may be movable between a high position in which the cutter 32 is spaced from the tape 9, and a lower position in which the cutting device is operable to cut the tape 9. Two clamps (not shown) may be provided for defining the positions respectively high and low of the carriage 66. Two sensors 69 and 71 emit signals respectively when the carriage 66 reaches its upper position and when it reaches its lower position.

The carriage 65 is connected to the piston rod 72 of a jack, for example a pneumatic jack, whose cylinder 73 is fixed to the frame 3. Thus, by actuating the jack 72, 73, the carriage 65 can be moved ' vo lonté between a first limit position, wherein the backup pad 31 is aligned with the hole 34 of the table 17, and a second limit position in which the cutting device 32 is aligned with said hole 34. stops ( not shown) may be provided to define the above two limit positions of the carriage 65. sensors can also be designed to emit signals respectively when the carriage 65 reaches its first limit position and when it arrives in its second limit position.

As shown in Figure 3, the cutting device 32 may comprise a carrier 74, fork-shaped, which is secured to the lower end of a hollow shaft 75 which extends perpendicularly to the table 17. The shaft 75 is rotatably mounted by suitable bearings in a bearing 70 fixed to the carriage 66. a shaft 76 extends inside the hollow shaft 75 and is fixed at its upper end to a plate 77, itself even attached to the carriage 66. the shaft 75 and the holder 74 can be rotated around the shaft 76 by a motor 78, for example an electric motor. A toothed pulley 79 fixed to the output shaft of the motor 78 transmits the rotary motion thereof, via a toothed belt 81, to another toothed pulley 82 fixed to the hollow shaft 75. least one cutting blade, preferably two cutting blades 83, constituted for example by scalpel blades are mounted on the support 74 and extend parallel to the axis of the shaft 76 equidistantly of said axis. Preferably, the two cutting blades 83 are adjustable in spacing from the axis of the shaft 76, so that their spacing can be adjusted according to the outer diameter of the lens on which the protective film is to be applied . For this purpose, each of the two cutting blades 83 is fixed to a blade holder 84. A screw 85 is rotatably mounted, at its two ends by suitable bearings in the two branches of the bracket 74 fork-shaped. The screw 85 has two threaded portions with not reversed, each of the two threaded portions being engaged in a corresponding threaded hole of one of the two door-blade 84. A bevel gear 86 is fixed to the screw 85 in its middle portion and is engaged with another bevel gear 87 which is fixed to the fixed shaft 76. Two guide parts 88 and 89, respectively attached to the slide door 84 prevent the latter from rotating with the screw 85, while allowing them to move along said screw. Thus, due to the meshing between the fixed gear 87 and the pinion 86, when the shaft 75 and the holder 74 are rotated by the motor 78, the two blade-gates 84 and blades 83 associated therewith are moved or away from each other depending on the direction of motor rotation 78. the pitches of the two threads of the screw 85 having known values ​​and the transmission ratio, which is defined by the two sprockets 86 and 87 and by the two pulleys 81 and 82, also having a known value, it is possible to adjust accurately, whenever desired, the distance between the two cutting blades 83, using for the engine 78 a stepper motor to not numerically controlled. Of the sensors 91,92 and 93 to control the rotation of the cutting device 32 and the position of the cutting blades 83.

The various sensors described above are electrically connected to a monitoring and control unit containing a microprocessor controlling the operation of the apparatus according to an operating cycle which will now be described.

The lens holder 29 being in its second position (away from the hole 34 of the table 17) waiting for a lens, a lens is placed on said support 29 manually by an operator or automatically by means of an appropriate transfer device . Then, the operator enters on a keyboard (not shown) the lens manufacturing L code, which code indicates in particular the microprocessor the value of the diameter D of the lens, so that the microprocessor will be able to rotate the motor 78 an appropriate number of revolutions to adjust the spacing of the two cutting blades 83 of the cutting device 32 to a slightly larger value (for example, D + 1 mm) than the diameter of the lens L placed on the holder 29. instead of returning the manufacturing code using a keypad, note that the code may have been registered in advance on the lens itself, such as a bar code. In the latter case, the device can be equipped with a code reader, which reads the bar code and transmits it to the microprocessor. Next, the operation cycle is initiated by a manual command issued by the operator and / or by an enable signal issued by a sensor (not shown) which may be provided on the support 29 and which outputs said enabling signal when it detects the presence of a lens on the support 29.

Then, the engine 4 is started for driving the spool 2 for winding it on the composite tape 9 and, consequently, in order to unroll it from the roll 8 of the coil 1. The motor 4 is stopped when a hole previously formed in the tape 9b of the composite tape 9 by the punching device 21 comes into coincidence with the hole 34 of the table 17. for example, the motor 4 can be stopped by the signal from a detector 94 (Figure 2), which is carried by the matrix 23 and which is arranged to detect passage of the trailing edge of a hole which has just been formed in the tape 9b by the punching device 21, provided of course that the path length followed by the tape 9b between the detector 94 and the hole edge 34 of the table 17 has been suitably adjusted beforehand so as to correspond to an integer multiple of the distance between the centers of two successive holes in the strip 9b by the device punching 21.

At the same time, the carrier 29 is moved by the actuator 53 in its first position (aligned with the hole 34 of the table 17). Immediately after stopping the motor 4, the actuator 42 is operated to tighten the composite tape 9 between the moveable jaw 35 and fixed jaw 17a. Then, the cylinder 64 is actuated to cause the backup pad 31 in its lower position in contact with the movable jaw 35. Then, the cylinder 46 is operated to move the carriage 44 and the support 29 upwards for pressing the lens L against the round portion of the adhesive side of the tape 9a, which is exposed through the hole 34 of the table 17 and through the tape hole 9b of the composite tape. In doing so, the lens L pushes the tape 9a against the backup pad 31 which, by deforming the shape of the upper face of the lens L. Since during this operation the composite tape 9 is held firmly by the jaws 35 and 17a and 9a since the adhesive tape is of a relatively extensible material, the adhesive tape is applied and bonded to the upper surface of the lens L without the formation of folds in said ribbon.

During application of the tape operation on the upper face of the lens L, the actuator 24 is operated to punch a new hole in the tape 9b.

Then, following a possible mode of operation of the device, the backup pad 31 is raised to its high position by the actuator 64 and the carriage 65 is moved to the left (as seen in Figures 1 and 3) means of the jack 73, to cause the cut 32 in the alignment device of the hole 34 of the table 17. in this position, the axis of the shaft 76 is axially aligned with the axis of the lens carried by the support 29. the cylinder 67 is then actuated so as to lower the cutting device with two blades 83 pierce the tape 9a. Assuming that the transmission ratio determined by the two pulleys 79 and 82 and by the two bevel gears 86 and 87 is 1 and the pitch of the two threads of the screw 85 is equal to 0.5mm, the motor 78 is then actuated so that its output shaft makes a half turn and that each of the two cutting blades 83 describes an arc of 180_° to cut the tape 9a. In reality, each of the two cutting blades 83 describes a spiral portion. Indeed, in addition to its rotational motion, each cutting blade moves, under the action of the screw 85 of 0.25 mm towards the edge of the lens L. As a result, the washer cut by the blades 83 in the tape 9a remains attached to said ribbon at two diametrically opposed points of the puck, but it is not a problem because the two attachment points are very small and can be easily broken at the time of the evacuation of the lens the washer with the adhesive adhered to its upper surface.

Then, the cutter 32 is raised into its upper position by means of the jack 67 and the carriage 65 is brought back by the jack 73 in its initial position in which the backup pad 31 is aligned with the hole 34 of the table 17 . at the same time, the carriage 44 is lowered to its low position by the jack 46, the support 29 is driven by the actuator 53 in its second position (away from the hole 34 of the table 17) to enable the evacuation of the lens L, manually or by means of a suitable transfer device, and the establishment of a new lens on the support 29, and the movable jaw 35 is spaced from the composite tape 9 by the actuator 42 to release said tape. Then, the motor 4 is actuated again and the cycle described above begins again with the new lens placed on the support 29.

According to another mode of operation, which is preferable to the mode of operation described above from the viewpoint of the duration of the operating cycle, after the tape 9a was applied on the upper face of the lens L as described previously , a vacuum in the space 95 between the adhesive tape 9a and the membrane 59 of the backup pad 31, to maintain the lens L in the backup pad 31. to this end, the movable jaw 35 comprises a passage 96 connected by a connector 97 and a pipe (not shown) to a vacuum source (also not shown). Then, the carriage 44 is moved to its lower position by the cylinder 46, which has the effect of lowering the carrier 29, but the lens L remains supported by the backup pad 31 at the same time under the effect of the adhesive tape 9a and under the effect of vacuum and space 95. Then, the support 29 is brought into its second position by the actuating device 53 in waiting for a new lens. Meanwhile, a transfer device (not shown) is brought below the hole 34 of the table 17 for supporting the lens L. Atmospheric pressure is then restored in the space 95 and the backup pad 31 is brought in its upper position by the cylinder 64. Then the carriage 65 is moved to bring it into the cutting device 32 the alignment of the hole 34 of the table 17, and said cutting device is actuated as described above to cut the adhesive tape 9a around the lens L. After the edge of this cutting operation, the cutting device is returned to its upper position by the jack 67, the carriage 65 is returned to its initial position by the actuator 73, the lens L with the washer adhesive bonded on the upper side is discharged to another processing station by the aforementioned transfer device, and finally the movable jaw 35 is spaced from the tape 9 by the actuator 42 to release said tape. A new operating cycle can then start again with a new lens previously positioned on the support 29 during the cutting operation of the tape 9a by the cutter 32.

A ribbon end detector 98 (Figure 1) causes the total shutdown of the unit and issuing a warning signal when it detects the end of the tape 9. In these circumstances, a new roll of ribbon 8 composite 9 is installed on the unwinding roller 1. at the front end of the composite tape 9 of the new roll 8, the adhesive tape 9a is separated from the peelable tape 9b and their front ends are butt jointed respectively to the rear ends, still present on the table 11 tape 9a and 9b the peelable ribbon of composite tape 9 previously used. In addition, if, at this time, the reel 2 reel is full, the composite tape 9 is advanced through the device until the new composite tape 9 reaches beyond the guide roller 19. The composite tape 9 is then cut, the perforated composite tape roll present on the reel spool 2 is removed and the front end of the new composite tape 9 is attached to the reel spool 2. the device is now ready to work again.

From the foregoing, it is clear that the method and apparatus of the present invention which have been described above make it possible to stick a protective film series on ophthalmic lenses, regardless of their diameter, without wrinkling protective film and with minimal human intervention to the extent that the apparatus can be largely automated. In addition, the apparatus can operate at a relatively high rate. According to reasonable estimates, the device can handle about one hundred and fifty lenses per hour.