EP0567894B1 - Device for guiding a workpiece or a tool while machining toric or spheric surfaces of ophtalmic lenses on grinding or polishing machines - Google Patents

Description

The invention relates to a device for guiding a workpiece or tool in the machining of toric or spherical surfaces of optical lenses on grinding or polishing machines, according to the preamble of claim 1. Such a device is known from DE-C-2 252 503.

The device is preferably intended for machining toric surfaces. A toric surface is understood to mean a non-rotationally symmetrical aspherical surface which has two radii of different sizes in two sections perpendicular to one another, while all other sections represent curves of a higher order. The clear grinding and polishing of the blanks of toric lenses is usually carried out using tools which have a continuous or interrupted toric surface which is complementary to the lens surface. It is essential that the two arcuate profiles of the toric lens are perpendicular to each other, especially in the case of correction lenses. It is therefore essential that in the course of clear grinding and polishing the two special perpendicular planes of the Grinding or polishing tools that are moved past a point on the surface of the lens always remain parallel to themselves. This means that mutual turning of the torus axes of the tool and lens must be avoided. Correspondingly, devices for clear grinding and polishing have a tool which is caused to carry out orbital movements which are as diverse as possible, but no rotary movement is provided around a vertical axis standing on the toric surface.

The devices for the clear grinding and polishing of toric lenses have a guide device which prevents such rotary movements and a driver device which ensures a change in position of the tool with respect to the lens. The driver device essentially has a ball joint, in the axial direction of which the tool's force of action acts on the lens, and which deflects the various movements which cause a relative change in position between the lens and tool, a direction perpendicular to its axis, and thus a gimbal balance between Allows lens and tool. A number of guide devices are known which operate on this principle.

Among the known guiding devices which are used for individual machining, there are those in which the lens or the tool is held in place, while the other element, ie the tool or the lens, is guided by forks, drive rods and / or joints, in particular ball joints . However, it should be noted that the guide systems working with a fork tend to make an eccentric adjustment, which prevents the torus from being fully realized. In another device, the lens or the tool is caused to rotate, while the other element, ie the tool or the lens, is guided by a device which also has forks, drive rods and / or joints. For devices for clear grinding and polishing in progressive operation, the devices used for guiding are structured accordingly.

All of these devices allow good quality toric surfaces to be obtained when properly adjusted. However, these complicated mechanical guiding devices are at least partially exposed to the abrasive grinding and polishing agents that are required for the clear grinding and polishing. Accordingly, the wear on such devices is high. The wear has the disadvantage that there is play in the joints and that this play brings with it a certain relative change in position of the two arcuate profiles of the lens, which are therefore less and less precisely delimited and can no longer be directed perpendicular to one another. This game occurs with all types of joints, especially with bearing and fork joints. Wear defects in the known guide devices result in a change in the characteristics of the surface of the lenses produced. These signs of wear are particularly exacerbated by the fact that considerable masses have to be moved in the aforementioned devices, which limits the relative speed between the tool and the workpiece, as a result of which the achievable chip removal volume is low and the machining time is correspondingly long.

The lining for optical lenses known from German patent specification 22 52 503 made a significant advance in relation to the problems shown. With this chuck, the orientation of the torus axes is not accomplished via forks and the two otherwise usual ball pins, but rather a form-fitting lens carrier is used, which is guided by a rolling bellows in the circumferential direction and which holds the intermediate piece to be machined by an air cushion to the tool (or vice versa). The lens carrier is designed to be axially displaceable, the radial guide being a spherical pin Tip occurs around which the lens wearer can execute an oscillating movement, which is necessary for the form-fitting homokinetic adjustment of the tool and lens. The effective contact pressure is transferred to the lens carrier via the roller bellows. The entire chuck thus forms a homokinetic coupling, which allows torque-free transmission of torque between the lens holder and the tool and, at the same time, hermetically seals the ball joint against the abrasive polishing and grinding agents.

Co. KG in DE-6330 Wetzlar) an einer axial bewegbaren Pinole verwendet, an deren innerem Ende das Aufnahmefutter konzentrisch befestigt ist. Infolge der bei der Rezeptglasbearbeitung üblichen unterschiedlichen Linsendicken und Werkzeughöhen muß hierbei die jeweilige Position der Pinole bei jedem Werkstück- bzw. Werkzeugwechsel neu eingestellt werden, um eine einwandfreie Funktion des Aufnahmefutters zu gewährleisten. Die bekannte Vorrichtung mit dem an sich vorteilhaften Rollbalg-Aufnahmefutter muß für die axialen Bewegungen von Hand betätigt werden. Auch der Werkstückwechsel kann nur von Hand vorgenommen werden.The known chuck described above is according to the prior art (Loh Toro-X 2000, grinding and polishing machine for the recipe production of the companies Loh Optikmaschinen KG in CH-4702 Oensingen and Wilhelm Loh Wetzlar Optikmaschinen GmbH

Co. KG in DE-6330 Wetzlar) used on an axially movable quill, on the inner end of which the receiving chuck is concentrically attached. As a result of the different lens thicknesses and tool heights customary in the processing of prescription glasses, the respective position of the quill must be readjusted each time the workpiece or tool is changed in order to ensure that the receiving chuck functions properly. The known device with the advantageous bellows receiving chuck must be operated by hand for the axial movements. Workpieces can also only be changed by hand.

The invention has for its object to provide a device based on the preamble of claim 1, in which to realize an automatic workpiece and tool change, the quill is automatically adjusted or adjusted and is held in the working position with optimal balancing effectiveness of the feed chuck.

The object is achieved by the characterizing features of patent claim 1. Advantageous developments of the invention are specified in subclaims 2 to 12 and also explained below.

According to the basic idea of the invention, the quill is axially moved by a pressure medium cylinder and piston arrangement through a pressure medium, which at the same time also actuates the receiving chuck and brings it into a position most suitable for homokinetic compensatory movements. In this way, all adjustment and delivery movements can be controlled exclusively and automatically by the pressure medium. This not only saves time, but it also achieves a consistently high processing quality. Gases and liquids can be used as pressure medium, but compressed air is preferred. The desired balance of forces between the forces generated by the pressure medium cylinder and piston arrangement and the forces acting in the receiving chuck is preferably achieved in accordance with claim 2.

In claim 3, an advantageous embodiment of the pressure medium cylinder and piston arrangement and the sleeve and the pressure medium connections between the individual pressure medium spaces are specified.

The measures of claim 4 ensure that not only the piston of the pressure medium cylinder and piston assembly is retracted after a working cycle, but that the intake chuck is brought into a position by the vacuum used, which favors an automatic change of the parts to be changed.

Claim 5 contains features for a special design of the parts forming the ball joint and their attachment to the quill. An expedient design of the guide pin carrying the ball head of the ball joint can be seen from claim 6.

Claims 7 and 8 characterize a stop arrangement for the guide pin with an integrated valve device for blocking the pressure medium supply to the receiving chuck when the guide pin is pushed out to the maximum.

For the processing of toric lenses, the design of the device according to claims 9 to 11 is advantageous. This ensures that the intermediate piece holding the lens is latched and positioned on the lens holder of the receiving chuck, which facilitates the automatic loading and positioning of the parts to be changed.

The device can also be designed according to claim 12.

Fig. 1

die für das Bearbeiten torischer Linsenflächen ausgebildete und in Arbeitsstellung abgebildete Vorrichtung im Längsschnitt,

Fig. 2

einen Schnitt durch das Aufnahmefutter in einem für Ausgleichsbewegungen zu stark aufgeblasenem Zustand,

Fig. 3

einen Schnitt durch das Aufnahmefutter in einem für Ausgleichsbewegungen zu schwach aufgeblasenem Zustand,

Fig. 4

einen Schnitt durch das Aufnahmefutter in einem für Ausgleichsbewegungen am besten geeigneten Aufblaszustand,

Fig. 5

einen gegenüber Fig. 1 vergrößerten Detailausschnitt entsprechend dem Ausschnittskreis V in Fig. 1 und

Fig. 6

einen gegenüber Fig. 1 vergrößerten Detailausschnitt entsprechend dem Ausschnittskreis VI in Fig. 1.

A preferred embodiment of the invention is described below with reference to the partially schematic drawings. It shows:

Fig. 1

the device designed for machining toric lens surfaces and shown in the working position in longitudinal section,

Fig. 2

a section through the feed in a state too inflated for compensating movements,

Fig. 3

a section through the feed in a state too weakly inflated for compensating movements,

Fig. 4

a section through the feed in an inflation state which is most suitable for compensating movements,

Fig. 5

an enlarged detail compared to FIG. 1 corresponding to the detail circle V in Fig. 1 and

Fig. 6

1 enlarged detail according to the detail circle VI in Fig. 1st

The device shown in Fig. 1 is part of a grinding or polishing machine, not shown, on which several of the devices shown (for example two) can be arranged in parallel. Such machines are used for prescription lens processing.

At the lower end of a quill 1, a rotationally symmetrical receiving chuck 2 is attached. The receiving chuck 2 has a bell-shaped flange 3 with a concentric hollow pin 4 and is non-rotatably and axially non-displaceably attached to the lower end of the sleeve 1 and fastened there in a suitable manner. The outer wall 7 of a bellows 8 is firmly and tightly clamped between a peripheral wall 5 of the flange 3 and an outer ring 6 attached to it. The inner wall 9 of the bellows 8 is fastened tightly to the cylindrical peripheral surface of a lens carrier 10. The bellows 8 consists of an elastomeric material with an embedded reinforcement insert, which does not hinder the bending of the bellows, but excludes its elastic expansion. The bellows can roll without being stretched and is rigid in the circumferential direction. Rotations of the lens carrier 10 relative to the flange 3 can therefore not occur in the machining operation. The rolling bellows 8 seals an articulated chamber 12 essentially delimited by the flange 3 and the lens carrier 10.

In the joint chamber 12 there is a ball joint consisting of a ball head 13 which engages in a ball socket 14 located in the lens carrier 10. The ball head 13 is located at the free end of a guide pin 15 which is guided in an axially displaceable piston-like manner within an axial bore 11 which is continuous over the length of the sleeve 1 and within a guide bush 16 inserted therein. The guide pin 15 has a longitudinal bore 17 closed at both ends, which is connected by an upper transverse bore 18 to the axial bore 11 and by a lower transverse bore 19 to the joint chamber 12 forming a pressure medium space.

The receiving chuck 2 with its ball joint 13, 14 and the rolling bellows 8 forms an exactly backlash-free, homokinetic coupling between the lens carrier 10 and the flange 3 in the circumferential direction because of the rigidity of the rolling bellows Rigid bellows 8 does not hinder the tiltability of the lens carrier 10 about the ball joint 13, 14 relative to the flange 3, so that tilting compensatory movements of the lens carrier 10 are possible without restriction. In addition, the bellows 8 hermetically seals the ball joint 13, 14 against the abrasive polishing and grinding agents.

For the processing of toric lenses, the lens carrier 10 is releasably locked to an intermediate piece 21, which is concentrically attached to it and holds the lens 20. For this purpose, as can be seen most clearly from FIG. 6, a circumferential inner groove 22 is provided on a lower cylindrical wall of the lens carrier 10 and a circumferential outer groove 23 is provided on a complementary cylindrical wall of the intermediate piece 21. An O-ring 24 is inserted into the circumferential inner groove 22, which is the locking element effective between the two grooves 22, 23. As can be seen in FIGS. 1 to 4, in the locked position, the intermediate piece 21 engages in a form-fitting and positioning manner in the lens carrier 10. The intermediate piece 21 sits on the grinding or polishing tool 25 with the interposition of the lens 20 fastened to it for processing.

The sleeve 1 can be moved axially in the manner described below by a pressure medium cylinder and piston arrangement arranged coaxially thereto. Here, the piston 26 is designed as an annular piston attached to the quill 1, which is displaceable within the cylinder 27 with the quill 1 acting as a piston rod. The cylinder 27 is closed at one end by an upper cylinder cover 29 provided with a pressure medium chamber 28. The pressure medium chamber 28 is located within a cup-shaped extension 30 of the cylinder cover 29. The upper end of the sleeve 1, which is immersed in the pressure medium chamber 28, is axially displaceable but non-rotatably guided in the upper cylinder cover 29. For this purpose, a guide ring is fastened axially immovably and non-rotatably within the upper cylinder cover 29. The Quill 1 passes through the guide ring 31 and is non-rotatable with respect to it by multi-spline toothing elements or the like, which are partly attached to the quill 1 above the piston 26 and partly in the corresponding through bore of the guide ring 31.

In the upper cylinder cover 29 there is a connection bore 32 for the optional supply of the pressure medium or the application of a negative pressure. The connection bore 32 is in constant communication with both the pressure medium chamber 28 and with a pressure medium space 33. The pressure medium space 33 is delimited by the cylinder 27, the upper cylinder cover 29, the outer surface of the sleeve 1 and the piston 26. Since there is no pressure difference between the pressure medium chamber 28 and the pressure medium space 33 due to the arrangement described, a seal between the sleeve 1 and the upper cylinder cover 29 or the guide ring 31 is omitted, as a result of which the sleeve 1 passes through the guide ring 31 with low friction.

With its end carrying the receiving chuck 2, the sleeve 1 is axially displaceably guided through a lower cylinder cover 34 which closes the lower end of the cylinder 27. Here too, a seal between the lower cylinder cover 34 and the sleeve 1 passed through it is not necessary to reduce friction because no pressure medium is supplied to the cylinder space between the piston 26 and the lower cylinder cover 34. This space is permanently connected to the outside atmosphere via a ventilation opening 35 which is guided through the lower cylinder cover 34. Of course, the two cylinder covers 29 and 34 and the cylinder 27 are held together by suitable means. The entire device can, for example, by means of the lower cylinder cover 34 on a crosshead or the like. the grinding and polishing machine, which is movably driven (not shown) in accordance with the kinematic requirements of machining toric surfaces.

The pressure medium space of the joint chamber 12 and the pressure medium space 33 of the pressure medium cylinder and piston arrangement 26, 27 communicate with one another, i.e. are directly connected to the connection bore 32 in the case of the pressure medium chamber 33 and indirectly in the case of the pressure medium chamber of the joint chamber 12. The pressure medium supplied via the connection bore 32 passes through a feed bore 36 in the upper cylinder cover 29 or in the guide ring 31 into the pressure medium chamber 33. At the same time, pressure medium of the same pressure passes from the connection bore 32 into the pressure medium chamber 28 and from there via the axial bore 11 in the sleeve 1 and via the bores 18, 17 and 19 in the guide pin 15 into the pressure medium chamber of the joint chamber 12. The pressure medium chamber of the joint chamber 12 and the pressure medium chamber 33 located above the piston 26 are therefore acted upon simultaneously by the pressure medium. For the function of the device, it is essential that there is a defined balance of forces in the working position of the device shown in FIG. 1. For this purpose, the dimensions of the pressure medium active surfaces on the piston 26, including the end ring surface of the quill 1 located in the pressure medium chamber 28, on the one hand, and the pressure medium active surfaces in the receiving chuck 2, on the other hand, are designed for a balance between the axially active forces directed in opposite directions in the working position. 1 and 4, in which in the area of the U-shaped transition between the outer wall 7 and the inner wall 9 of the bellows 8 there are symmetrical relationships with respect to a center line between the walls 7 and 9 . This working position of the bellows 8 ensures optimal homokinetic compensatory movements between the flange 3 and the lens carrier 10 of the receiving chuck 2.

Tilting movements, ie compensating movements of the lens carrier 10, on the other hand, are made more difficult or at least restricted if the bellows 8 have the configuration shown in FIGS. 2 and 3 shows. In FIG. 2 the pressure medium applied to the receiving chuck 2 is too high, while in FIG. 3 it is too low. In both cases there is a tightening of the bellows which impairs the tilting ability of the rolling bellows 8. In the ideal state, the sleeve 1 and the receiving chuck 2 assume approximately the position shown in FIG. 1, in which the aforementioned balance of forces is present and a sufficient contact pressure is applied between the workpiece and the tool for the intended machining process.

The guide pin 15 also has a special feature illustrated by FIG. 5. When it is acted upon by the pressure medium on its end face, its outward displacement path is limited by a stop. For this purpose, an O-ring 37 inserted into a circumferential groove of the same is provided at the upper end of the guide pin 15 and, when the guide pin is pushed out to the maximum, strikes the end face 38 of the guide bush 16 inserted into the axial bore 11 of the sleeve 1. This arrangement also acts as a valve device. When the guide pin 15 is pushed out as far as possible, the connection between the axial bore 11 of the sleeve 1 and the longitudinal bore 17 of the guide pin 15 is interrupted because the upper transverse bore 18 is completely covered by the guide bush 16 and the O-ring 37 of the end face 38 lies sealingly. In this position, no pressure medium can get into the pressure medium chamber of the joint chamber 12, so that the bellows 8 and the movable inner parts attached to it are prevented from moving too far forward.

The mode of operation of the device according to the invention is explained below.

The device is moved into the working position by supplying the pressure medium to the connection bore 32. Here, the pressure medium flows through the connection bore 32 into the pressure medium space 33, the pressure medium chamber 28 and via the bores described in the pressure medium space of the joint chamber 12. As a result, the rolling bellows 8 with the lens carrier 10 and the intermediate piece 21 holding the lens 20 is extended downward in the receiving chuck 2, the stop arrangement described with valve device at the upper end the guide pin 15 prevents an ancestor from being too wide. At the same time, the piston 26 extends with the sleeve 1 until the workpiece, ie the lens 20, is pressed against the tool to the extent necessary for the machining. In this working position, the described balance of forces is automatically set, in which the rolling bellows 8 is in its ideal configuration shown in FIGS. 1 and 4 and therefore permits the necessary compensating movements during processing. Working pressures of the pressure medium between 0.1 and 1.0 bar are sufficient for all applications. With plastic glasses, the working pressure is between about 0.2 to 0.4 bar, while with mineral glasses, working pressures up to 1.0 bar may be required. The minimum working pressure is about 0.1 bar to overcome the internal friction of the device.

After the grinding or polishing process has ended, the device is returned to its starting position, the sleeve 1 being returned to its loading and starting position by applying a negative pressure via the connection bore 32 to the pressure medium chamber 33. Here, the lens carrier 10 with the intermediate piece 21 and the processed lens 20 located thereon is lifted off the tool 25. Since the negative pressure applied also acts on the pressure medium space of the joint chamber 12 via the bores and spaces described, the membrane formed by the bellows 8 and the lens carrier 10 with the intermediate piece 21 and the lens 20 is pulled against the bell-shaped flange 3 against the stop . As a result, the precise positioning of the workpiece or of the parts carrying the workpiece required for automatic loading is achieved. By the positive engagement of the intermediate piece 21 with the lens holder 10 and the locking of these two parts, a secure positioning of the parts holding the workpiece on the receiving chuck 2 and holding the lens holder 10 together with the intermediate piece 21 is achieved. This is particularly important in order to ensure a safe separation of lens 20 and tool 25 at the end of the processing. The latching between the lens carrier 10 and the intermediate piece 21 enables the parts to be changed that are necessary for automatic loading to be positioned.

In the context of the present invention, it is also possible in principle to axially fix the relative position of sleeve 1 and cylinder 27 when the working position is reached. In this case, axial compensating movements would have to be taken over by the receiving chuck 2.

Claims (12)

1. Device for guiding a workpiece or tool in the machining of toric or spherical surfaces of optical lenses on grinding or polishing machines, comprising
   a seating chuck (2) having a lens support or tool support (10), a connecting component, consisting of a journal (4) and a bell-shaped flange (3), for fitting of the chuck, a ball joint (13, 14) connecting the lens support or tool support to the connecting component, a roller bellows (8), non-resilient in the circumferential direction and connecting together the flange and the lens or tool support, which bellows seals the space hereinafter known as joint chamber (12) in which the ball joint is situated, and a pressure fluid line connected to the joint chamber, and
   an axially movable spindle sleeve (1), disposed on the grinding or polishing machine, to the inner end of which the seating chuck is concentrically fixed,
   characterized in that,
   the spindle sleeve (1) is movable by a pressure fluid cylinder-piston assembly (26, 27), disposed coaxially thereto, and the pressure fluid spaces of the joint chamber (12) and of the pressure fluid cylinder-piston assembly (26, 27) are connected together and can be charged simultaneously with the pressure fluid.
2. Device according to Claim 1, characterized in that the pressure fluid active surfaces on the piston (26) and in the seating chuck (2) are designed for equilibrium between the axial forces acting in opposite directions in the working position.
3. Device according to Claim 1 or 2, characterized in that the piston (26) is constructed as an annular piston fixed to the spindle sleeve (1), that the cylinder (27) is closed at one end by a first cylinder head (29), provided with a pressure fluid chamber (28), into which the end of the spindle sleeve (1) remote from the seating chuck (2) penetrates, that the spindle sleeve (1) is guided, axially displaceably but non-rotatably, in the first cylinder head (29) and passes axially displaceably, with its end carrying the seating chuck (2), through a second cylinder head (34) closing the other end of the cylinder (27), and that the pressure fluid space (33) bounded by the cylinder (27), the first cylinder head (29), the spindle sleeve outer surface and the piston (26), is connected to the pressure fluid chamber (28), which in turn is connected to the pressure fluid space of the joint chamber (12) via a continuous axial bore (11) of the spindle sleeve (1).
4. Device according to one of Claims 1 to 3, characterized in that the spindle sleeve (1) can be reset to its feed starting position by application of a vacuum to the pressure fluid space (33) bounded by the cylinder (27), the first cylinder head (29), the outer surface of the spindle sleeve and the piston (26).
5. Device according to one of Claims 1 to 4, characterized in that, in the axial bore (11) of the spindle sleeve (1), a guide pin (15) extending into the pressure fluid space of the joint chamber (12) is axially displaceably guided in the manner of a piston, which pin carries, at its free end, the ball end (13) of the ball joint, which engages into the ball cup (14) of the ball joint situated in the lens or tool support (10), the guide pin (15) providing, via a longitudinal bore (17), the communication between the axial bore (11) of the spindle sleeve (1) and the pressure fluid space of the joint chamber (12).
6. Device according to Claim 5, characterized in that the longitudinal bore (17) of the guide pin (15) is closed at both ends, the connection between the longitudinal bore (17) and the axial bore (11) of the spindle sleeve (1) and with the pressure fluid space of the joint chamber (12) being made by transverse bores (18, 19) in the guide pin (15).
7. Device according to one of Claims 5 and 6, characterized in that the outwardly orientated displacement travel of the guide pin (15) is limited by a stop, with which is associated a valve device, by which, when the guide pin (15) is extended to its maximum, the connection between the axial bore (11) of the spindle sleeve (1) and the longitudinal bore (17) of the guide pin (15) is interrupted.
8. Device according to Claim 7, characterized in that, at one end of the guide pin (15), an O-ring (37) seated in a circumferential groove of same is provided, which, when the guide pin (15) is extended to the maximum, strikes against the end face (38) of a guide bushing (16) inserted into the axial bore (11) of the spindle sleeve (1) and at the same time forms, together with this end face, the valve device.
9. Device according to one of Claims 1 to 8, characterized in that, for the machining of toric lenses, the lens support (10) is releasably locked to an intermediate component, mounted concentrically thereto and holding the lens (20).
10. Device according to Claim 9, characterized in that, for the purpose of the locking, a circumferential inner groove (22) is provided on the lens support (10) and a circumferential outer groove (23) on the intermediate component (21), an O-ring (24) being seated in the circumferential inner groove (22).
11. Device according to Claim 9 or 10, characterized in that, in the locked position, the intermediate component (21) engages form-fittingly and positioningly into the lens support (10).
12. Device according to one of Claims 1 to 11, characterized in that the spindle sleeve (1) can be axially secured relative to the cylinder (27) in the working position.

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