GB2425499A

GB2425499A - Working a surface in a fluid bath

Info

Publication number: GB2425499A
Application number: GB0607134A
Authority: GB
Inventors: Wolfgang Rupp
Original assignee: Carl Zeiss SMT GmbH
Current assignee: Carl Zeiss SMT GmbH
Priority date: 2005-04-25
Filing date: 2006-04-10
Publication date: 2006-11-01
Also published as: GB0607134D0

Abstract

A method of grinding, lapping, honing or polishing a surface of a workpiece 2 by immersing a contact area between the workpiece 2 and a tool 3.1 in a bath 9 of working fluid 10 and then working the surface of the workpiece 2 using the tool 3.1 at the contact area. Flow of working fluid 10 into the contact area is assisted by ducts in the tool (203.9, Fig. 4) and by interrupting working and moving the tool 3.1 away from the workpiece 2. The working fluid 10 is circulated within the bath 9 by means of an agitator 13 located therein. During working the bath 9 is moved either in response to tool movement or in synchronicity therewith. Preferably the workpiece 2 lies between two tools 3.1 and 4.1. After working has been completed the working fluid 10 is at least partly replaced with a cleaning fluid. The method may be used to make LCD masks.

Description

I 2425499

DEVICE AND METHOD FOR SURFACE WORKING

BACKGROUND OF THE INVENTION

The invention relates to a method for the surface working of a body, in particular an LCD mask. The invention further relates to a corresponding device for the surface working of a body.

Surfaces with a particularly high surface quality, especially a low surface roughness, are required for numerous applications in the optical industry but also in other branches of in- dustry. Two high-quality surfaces parallel to one another are required, in particular, for comparatively thin LCD masks, such as those used for flat screens. In order to achieve a high surface quality, a plurality of different methods are known for fine surface working, for exam- ple, grinding, in particular precision grinding, lapping, honing, polishing etc. With all these methods, in order to achieve a high surface quality, it is necessary to achieve a removal of material which is as uniform as possible over the entire surface of the body.

Two different working methods are usually used for the fine working of plane surfaces of bodies. With the so-called single-disk method, the body to be worked is affixed to a support.

The body is then guided by corresponding support kinematics in circular, oscillating move- ments over a rotating disk-shaped tool. Thus, an epicycloidal relative movement between the body and the tool is achieved. The epicycloids formed can be guided over the body in a sur- face-covering fashion by suitably controlling the speeds of the guide and tool movements and the excursions of the guide movement such that a homogeneous removal of material is achieved.

A disadvantage with these single-disk methods is that working of the body is in each case only possible from one side such that strong requirements with respect to parallelism of two surfaces can only be satisfied at very high expenditure. In addition, the body must be affixed to the support in an expensive fashion to be as free from stresses as possible. In addition, not least for this reason, only a comparatively low removal performance can be achieved.

Higher removal performances can be achieved using so-called double-disk methods in which the body is guided between two rotating parallel diskshaped tools. In order to counteract any inhomogeneous removal of material due to the decrease of the circumferential speed towards the center of the rotating disk, in a corresponding device, the body to be worked is guided by a planet wheel of a planetary-gearing-like guide device. In this case, predeter- mined by the geometry of the guide device, a plane guide movement of the body in two di- rections running transverse to one another is obtained. As a result of the superposition with a rotary movement of the respective tool, an epicycloidal relative movement between body and tool is also obtained here. The epicycloids formed in this case can be guided over the body in a surface-covering fashion by suitably controlling the speeds of the guide and tool movements such that a homogeneous removal of material is achieved.

ia Thanks to the arrangement of the body to be worked between the two tool disks, higher contact pressures and, therefore, a higher removal performance can be achieved compared to the single-disk method, but comparatively narrow limits are imposed on the transverse dimensions of the body for a predetermined size of working device. This is because, as a result of the planetary-gearing-like guide device, at any time only one ring-segment-shaped area of the tool disks can be used. The ratio of the diameter of a tool disk to the maximum transverse dimension of a body to be worked is usually at about 3.5 to 4. In order to work bodies having larger transverse dimensions, considerably larger devices are therefore re- quired. With such large devices however, considerable problems arise with regard to main- taining the working precision which can only be overcome, if at all, at very great expense.

With both, single-disk methods and double-disk methods, a working fluid is usually continu- ously supplied to the contact area between the respective disk and the body to be worked.

This working fluid supply is generally achieved by corresponding working fluid pumps and working fluid ducts guiding the working fluid into or close to said contact area. Usually, a jet or spray of working fluid is directed onto either one of the respective disk and the body such that a working fluid film builds up thereon. The working fluid film is drawn into the contact area leading to a working fluid layer between the respective disk and the body to be worked.

The working fluid then typically flows off towards a remote accumulation area, wherefrom it is drawn to be eventually reconditioned and recycled.

Several problems arise with this type of working fluid supply. One problem is that, depending on the contact pressure between the disk and the body as well as the wetting properties of the working fluid, a defective working fluid layer may form between the respective disk and the body leading to an undesired locally "dry" contact between the respective disk and the body. In particular, such a "dry" contact may have adverse effects on the surface quality of the body obtained from the working process.

A further problem is that fractions of the working fluid may accumulate and dry at locations of the disk and/or the body temporarily remote from their contact area. As soon as such loca- tions become part of the contact area, e.g. due to a corresponding movement of the disk and/or the body, the dried working fluid has adverse effects on the surface quality of the body obtained from the working process.

SUMMARY OF THE INVENTION

It is thus an object of the invention to provide a device and a method for surface working which does not or at least to a lesser extent have the aforesaid disadvantages and especially makes it possible to economically achieve a high quality of the surfaces to be worked.

The invention is based on the cognition that the above disadvantages may be avoided and a high quality of the surfaces to be worked may be achieved if at least a part of the contact area between the respective tool and the body to be worked is immersed in a working fluid bath.

Unlike in the known devices, depending on the immersion depth, a considerable hydrostatic pressure may build up in the working fluid in the immersed part of the contact area. This hy- drostatic pressure promotes the buildup of a non-defective working fluid layer between the respective tool and the body to be worked, avoiding "dry" contact and leading to high quality surfaces. Furthermore, the immersion prevents local drying of the working fluid on the sur- face of the tool or the body to be worked.

One object of the invention is thus a method for surface working of a body having at least a first surface to be worked. The method comprises providing a first tool with a first working surface and providing a working fluid container. In a preparation step, a working fluid bath is established within said working fluid container and at least one of said body, said first tool and said container is positioned such that said first working surface contacts said first sur- face in a first contact area and at least a part of said first contact area is immersed in said working fluid bath. In a working step subsequent to the preparation step, the first surface is worked with the first working surface.

A further object of the invention is a device for surface working of a body having a first sur- face to be worked. The device comprises a first tool with a first working surface and a work- ing fluid container adapted to receive a working fluid to form a working fluid bath. The first tool, for working the first surface, is adapted to contact the first surface with the first working surface in a first contact area. The working fluid container is arranged such that, when working the first surface, at least a part of the first contact area is immersed in the working fluid bath.

Further aspects and embodiments of the invention will become apparent from the dependent claims and the following description of preferred embodiments which refers to the appended figures. All combinations of the features disclosed, whether explicitly recited in the claims or not, are within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

io Figure 1 is a schematic diagram of a preferred embodiment of the device for surface working according to the invention for executing a preferred embodiment of the method for surface working according to the invention; Figure 2 is a block diagram of a preferred embodiment of a method for surface working executed with the device for surface working of Figure 1; Figure 3 is a schematic partial view of a further preferred embodiment of the device for surface working according to the invention; Figure 4 is a schematic partial view of a further preferred embodiment of the device for surface working according to the invention; Figure 5 is a block diagram of a preferred embodiment of a method for surface working executed with the device for surface working of Figure 4.

DETAILED DESCRIPTION OF THE INVENTION

First embodiment In the following, a first preferred embodiment of a device 1 for surface working according to the invention, with which a preferred embodiment of the method according to the invention may be executed, is described with reference to Figures 1 and 2.

tigure 1 shows a schematic partially sectional view of the device 1 with which the surfaces of a body 2 can be worked by means of a first tool 3.1 of a first tool device 3 and a second tool 4.1 of a second tool device 4.

In the embodiment shown, the body 2 is an LCD mask for a flat screen shown with an ex- aggerated thickness for reasons of better visibility. However, it is to be understood that, with the device 1, any other bodies for which a corresponding surface quality is required may also undergo corresponding surface working.

The first tool device 3 is arranged on a displaceable first traverse 5.1 supported at its both ends on a machine frame 5. In Figure 1, the first traverse 5.1 is shown in its operating posi- tion. As indicated by the dashed contour 6.1, the first traverse 5.1 and, thus, the first tool device 3 may be driven by a first traverse drive 5.3 along a first direction 7.1 to a displace- ment position at a distance from the second tool device 4 in which the body 2 can be in- serted into the device 1. For working the body 2 the first traverse 5.1 is driven into its oper- ating position. In this operating position of the first traverse 5.1, the tool 3.1 is located above the body2.

When the first traverse 5.1 is located in its operating position, the tool 3.1 for the working of the body 2 is displaced by a first tool drive device 3.2 along the first tool axis 3.3, i.e. along a second direction 7.2, in the direction of the body 2 until the first tool 3.1 in its operating posi- tion abuts against the body 2 with a predetermined contact pressure.

The first tool 3.1 is a circular-disk-shaped tool with a first disk carrier 3.4 and a first working disk 3.5 which is exchangeably affixed to the first disk carrier 3.4. The first disk carrier 3.4 is connected to the first tool drive device 3.2 via a shaft 3.6 connected to the first disk carrier 3.4 via a cardanic mount covered by a bellows. Depending on the application, the first work- ing disk 3.5 may be a grinding disk, a lapping disk, a honing disk, a polishing disk or a disk for any other type of surface working.

The second tool device 4 is arranged below the receptacle for the body 2. The second tool device 4 is arranged on a second displaceable traverse 5. 4 supported at its both ends on the machine frame 5. In Figure 1, the second traverse 5.4 is shown in its operating position as well.

The second tool 4.1 also comprises a circular-disk-shaped tool with a second disk carrier 4.4 and a second working disk 4.5 which is exchangeably affixed to the second disk carrier 4.4.

The second disk carrier 4.4 is connected to the second tool drive device 4.2 via a shaft 4.6 connected to the second disk carrier 4.4 via a cardanic mount covered by a bellows. De- pending on the application, the second working disk 4.5 may be a grinding disk, a lapping disk, a honing disk, a polishing disk or a disk for any other type of surface working.

For working the body 2, the second tool 4.1 is displaced - if necessary by the second tool drive device 4.2 along the second tool axis 4.3, i.e. along the second direction 7.2, in the direction of the body 2 until the second tool 4.1 is located in its operating position. The oper- ating position of the second tool 4.1 is defined by a pre-definable position along the second tool axis 4.3.

When the second tool 4.1 is located in this operating position, the body 2 is inserted into the device 1, wherein it then rests on the second tool 4.1. At the time of insertion of the body 2, the first tool 3.1 is still located in its displacement position indicated by contour 6.1 in Figure 1, i.e. at a distance from the body 2. The contact pressure between the second tool 4.1 and the body 2 is then mainly produced by means of the first tool device 3 which has been driven to its operating position, such that it abuts against the body 2 with a pre-defined contact pressure. This contact pressure can be varied during working the body 2 by the first tool drive device 3.2 if the application requires this.

It is to be understood here that, with other variants of the invention, it may also be provided that the contact pressure between the tools and the body may be adjusted via the second tool device. It may likewise be provided that this pressure is detected and controlled by means of both tool devices.

As can be seen from Figure 1, for working the body 2, the first tool 3.1 lies opposite to the second tool 4.1. Thus, a working gap 1.1 is formed between them, in which the body 2 is arranged. The working gap 1.1 mainly extends in a working gap plane which runs perpen- dicular to the tool axes 3.3 and 4.3.

In the representation of Figure 1, the first tool axis 3.3 is in direct alignment with the second tool axis 4.3. For certain applications, however, it may be favorable or necessary that the two tool axes 3.3 and 4.3 are offset transverse to one another. In order to achieve this, the first tool device 3 may be displaced in the direction of the double arrow 7.1 by means of the trav- erse drive 5.3 as it is indicated in Figure 1 by the dashed contour 6.2. Additionally or alterna- tively, the first tool device 3 may be displaced perpendicularly to the drawing plane of Figure 1 for this purpose by a first transverse drive integrated into the first tool drive device 3.2.

Additionally or alternatively, in order to achieve the above offset, the second tool device 4 may be displaced in the direction of the double arrow 7.1 by means of the second traverse drive 5.5. Additionally or alternatively, the second tool device 4 may be displaced perpen- dicularly to the drawing plane of Figure 1 for this purpose by a second transverse drive inte- grated into the second tool drive device 4.2.

If necessary, some or all of the above displacement movements of the first tool device 3 and the second tool device 4 may also take place during the working of the body 2 with an arbi- trarily pre-definable movement profile.

If the application requires it, during working the body 2, the first tool 3.1 may execute a first rotary tool movement about its tool axis 3.3 along a first rotary direction 3.7. This first rotary tool movement may be effected by the first tool drive device 3.2. Additionally or alternatively, if the application requires it, during working the body 2, the second tool 4.1 may execute a second rotary tool movement about its tool axis 4.3 along a second rotary direction 4.7. This second rotary tool movement may be effected by the second tool drive device 4.2. Again, if necessary, either one of the above rotary tool movements of the first tool 3.1 and the second tool 4.1 may take place with an arbitrarily predefinable movement profile.

The body 2, when arranged in the working gap 1.1 between the two tools 3. 1 and 4.1 located in their operating position, is held In the working gap plane by a holder 8. The holder com- prises an inner frame 8.1 connected to an outer frame 8.2 via several struts 8.3 evenly dis- tributed at its circumference.

Supported in the inner frame 8.1 is a cage 8.4 which has a receptacle in the form of a re- ceiving opening for receiving the body 2. The cage 8.4 is freely rotatable about an axis run- ning perpendicular to the plane of the inner frame 8.1. It is hereby achieved that, in cases of increased contact force with the tool which may occur locally as a result of local inhomoge- neities, the body 2 can yield so that, during working, forces as uniform as possible act on the body 2. However, it is to be understood that, for certain applications, especially in order to achieve a higher removal of material, it may be provided to fix the cage 8.4 with respect to the inner frame 8.1. For this purpose, corresponding fixing means - not shown - are pro- vided.

In the embodiment shown in Figure 1, the outer frame 8.2 is fixedly mounted to the machine frame 5. Anyway, it is to be understood that, with other variants of the invention, the outer frame of the holder may be displaceable in parallel to the plane of the working gap 1.1. Thus guide movements of an arbitrary movement profile parallel to the plane of the working gap 1.1 may be imposed on the body 2.

A working fluid container 9 is mounted to the second tool device 4. The working fluid con- tainer 9 receives a working fluid bath 10.1 of a working fluid 10. The working fluid bath 10.1 is established by a working fluid supply device 11 connected to the working fluid container 9 and supplying working fluid 10 to the working fluid container 9.

The working fluid container 9 is arranged such that the shaft 4.6 of the second tool device 4 is led - in a fluid tight manner - through the boffom wall of the working fluid container 9.

Thus, when displacing the second tool device 4, the entire working fluid container 9 is dis- io placed in synchronicity with the second tool device 4. This has the advantage that the work- ing fluid container 9 may be kept small in size and that the sealing between the shaft 4.6 and the working fluid container 9 may be realized comparatively easily.

It will be appreciated that, with other embodiments of the invention, the working fluid con- tainer may be directly mounted to the second tool as it is indicated in Figure 1 by the dashed contour 9.2.

In the following, a preferred embodiment of the method for surface working according to the invention is described with reference to Figures 1 and 2.

In a first step 12.1, the first tool 3.1 and the second tool 4.1 and the working fluid container 9 for the working fluid bath 10.1 are provided as a part of the device 1 to provide a configura- tion as it has been described above in the context of Figure 1.

In a subsequent preparation step 12.2, the configuration as shown in Figure 1 is established.

To this end, in a positioning step 12.3, the body 2 is placed between the first tool 3.1 and the second tool 4.1 such that the first tool 3.1, the body 2 and the second tool 4.1 are located within the working fluid container 9. Thereby, the body 2 is placed into the receptacle of the cage 8.4 of the holder 8 after the second tool 4.1 has been brought in an operating position.

At the time of insertion of the body 2, the first tool 3.1 is still located in its displacement posi- tion 6.1 shown in Figure 1, i.e. at a distance from the body 2.

Then, the first tool 3.1 is displaced into its operating position, wherein said first tool 3.labuts with its substantially plane first working surface 3.6 against the substantially plane first sur- face 2.1 of the body 2, said first surface 2.1 being one of the surfaces to be worked. Thus, the first working surface 3.6 contacts the first surface 2.1 in a first contact area 1.2 extending over the entire first surface 2.1.

Similarly, in the operating position of the second tool 4.1, said second tool 4.1 abuts with its substantially plane second working surface 4.6 against the substantially plane second sur- face 22 of the body 2, said second surface 2.2 being the second one of the surfaces to be worked. Thus, the second working surface 4.6 contacts the second surface 2.2 in a second contact area 1.3 extending over the entire second surface 2.2.

In a working fluid bath establishing step 12.4, subsequent to the positioning step 12.3, the working fluid bath 10.1 is established by the working fluid supply device 11 supplying work- ing fluid 10 to the working fluid container 9. The surface level 10.2 of the working fluid bath 10.1 is adjusted such that, both, the first contact area 1.2 between the first tool 3.1 and the body 2 and the second contact area 1.3 between the second tool 4.1 and the body 2 are completely immersed in the working fluid bath 10.1.

The immersion of the respective contact area 1.2 and 1.3 provides the advantage that, de- pending on the height of the surface level 10.2 of the working fluid bath 10.1 above the re- spective contact area 1.2 and 1.3, a considerable hydrostatic pressure builds up in the working fluid 10 in the region of the respective contact area 1.2 and 1.3. This hydrostatic pressure promotes a continuous and non- defective layer of working fluid 10 between the respective tool 3.1 and 4. 1 and the body 2 over the entire respective contact area 1.2 and 1.3. Such a continuous and non-defective layer of working fluid 10 promotes high quality surface working results.

To further promote such a continuous and non-defective layer of working fluid 10 over the entire respective contact area 1.2 and 1.3, each of the tools 3.1 and 4.1 is provided with a number of working fluid ducts 3.9 and 4.9, respectively. These working fluid ducts 3.9 and 4.9 communicate with the working fluid bath 10.1 and guide working fluid 10 towards differ- ent regions of the respective contact area 1.2 and 1.3.

A further advantage of the complete immersion of the respective contact area 1.2 and 1.3 lies within the fact that, during working, no local drying of the working fluid either on the sur- face of the body 2 or on the working surface of one of the tools 3.1 and 4.1 may occur.

It will be appreciated that, with other embodiments of the invention, a different number of such working fluid ducts may be provided. Furthermore, such working fluid ducts may be omitted as well if sufficient working fluid supply to the respective contact area is guaranteed by other circumstances, e.g. a sufficiently high hydrostatic pressure etc. It will be further appreciated that, with other embodiments of the invention, the working fluid bath establishing step may be executed prior to the positioning step. Thus, the body may be placed between the tools after completed establishment of the working fluid bath.

Furthermore, it is also possible to execute the positioning step and the working fluid bath establishing step at least partly simultaneously. For example, the working fluid bath surface level may be raised or lowered only to about the level of the inner frame of the holder for the body such that the second working surface of the second tool is slightly covered with work- ing fluid. Then, the body may rapidly and easily be inserted into the device without any sub- stantial resistance of the working fluid. The coverage of the second working surface of the second tool with working fluid thereby promotes a continuous and non-defective layer of working fluid over the entire second contact area. After insertion of the body, the first tool may be positioned while simultaneously raising the working fluid bath surface level. Prefera- bly, the raising working fluid bath floods the first surface of the body before the first tool contacts the first surface. Thus, hereby as well, a continuous and non-defective layer of working fluid over the entire first contact area is promoted.

In a working step 12.5, subsequent to the preparation step 12.2, the first surface 2.1 of the body 2 is then worked with the first tool 3.1 while the second surface 2.2 of the body 2 is worked with the second tool 4.1 as it has been described above in the context of Figure 1.

Preferably, rotary tool movements and displacement movements of the tools 3.1 and 4.1 and, eventually, displacement movements of the body 2 are superimposed such that an epi- cycloidal relative movement is produced between the body 2 and the respective tool 3.1 and 4.1.

A control device - not shown - controls the respective drive devices 3.2, 4.2, 5.3 and 5.5 connected thereto such that, as a result of the superposition of the tool and guide move- ments, over the entire first surface 2.1 to be worked and the entire second surface 2.2 to be worked, a uniform removal of material and, thus, a uniform surface quality are obtained. By the term uniform surface quality should be understood, in the sense of the present applica- tion, that the surface roughness over the surface to be worked varies by less than 30% of an average value of the surface roughness.

The control is executed such that the amount of the relative speed between the respective surface to be worked and the associated working surface is subject to as little variation as possible at every point. Particularly favorable force ratios are hereby achieved during the working which result in a high surface quality. In particular, the control is executed such that the amount of this relative speed is never zero at any point in time. The movements can be superposed for this purpose such that, overall, a sinusoidal relative movement is obtained.

Anyway, it will be appreciated that, with other embodiments of the invention, depending on the requirements of the surfaces to be worked, any other suitable movement profile may be chosen.

To further promote the continuous and non-defective layer of working fluid 10 over the entire respective contact area 1.2 and 1.3, the contact pressure between the respective tool 3.1 and 4.1 and the body 2 is intermittently temporarily lowered. To this end, the first tool 3.1 is intermittently moved back and forth along the second direction 7.2. Thus, the first tool 3.1 is shortly moved away from the body 2. Due to this movement, form the surroundings and via the working fluid ducts 3.9 and 4. 9, respectively, fresh working fluid 10 iS sucked into both, the first contact area 1.2 and the second contact area 1.3. After a period of sufficient length the contact pressure is then re-established by reapproaching the first tool 3.1 to the body 2.

The amount by which the first tool 3.1 is intermittently retracted from the body 2 depends on the application, in particular on the viscosity and the wetting properties of the working fluid as well as on the actual and required surface roughness of the body. In some applications, for example, a few tenths of millimeters may be sufficient.

To prevent sedimentation effects etc. within the working fluid bath 10.1 and to achieve a fa- vorable temperature distribution within the working fluid bath 10.1, during said working step 12.4, a circulation is established in the working fluid bath 10.1. This is achieved by an agitator 13 sitting on the shaft 4.6 of the second tool device 4 and rotated with this shaft 4.6.

It will be appreciated that, with other embodiments of the invention, agitator means, such as small vanes or the like, may be distributed at the outer circumference of one or both tools to establish, upon rotation of the respective tool, a circulation within the working fluid bath 10.1.

These agitator means may be adapted to provide a flow of working fluid 10 towards the working gap 1.1 to promote a continuous and non-defective layer of working fluid 10 be- tween the respective tool 3.1 and 4.1 and the body 2 over the entire respective contact area 1.2andl.3. It will be further appreciated that, with other embodiments of the

invention, the circulation within the working fluid bath may be achieved by other means. For example, it may be pro- vided by the working fluid supply device 11 supplying fresh working fluid 10 to the working iluid container 9 and withdrawing used working fluid 10 from the working fluid container 9 at a sufficient rate. Additionally or alternatively, the entire working fluid container 9 may also be rotated together with the shaft 4.6 of the second tool device 4. Furthermore, one or more separately driven agitators or the like may be provided as well.

At the end of the working step 12.4, the body 2 is removed from the device 1. To this end, preferably, the level of the working fluid bath surface 10.2 is lowered so far that the body 2 may be taken out of the device 1 without inadmissibly high stresses due to its flow resis- tance. If, for example, any such stresses are to be avoided, the level of the working fluid bath surface 10.2 may be lowered to about the level of second working surface 4.8. Then, the body may rapidly and easily be taken out of the device 1 using a corresponding handling device, It will be appreciated that, to facilitate this, the second tool 4.1 may be lifted along its axis 4.3.

It will be further appreciated that, depending on the weight of the body 2 and the required uniformity in the surface quality of the two surfaces 2.1 and 2.2 to be worked, the body 2 may be may be turned around, reintroduced - upside down - into the device 1 and worked as described above to eliminate or at least reduce the effects of gravity on the working result.

In a cleaning step 12.5, subsequent to the working step 12.4, the working fluid 10 within the working fluid container 9 is substantially completely replaced by a cleaning fluid such as water or the like. The cleaning fluid may be provided by the working fluid supply device 11 as well after the working fluid supply device 11 has withdrawn substantially all the working fluid from the working fluid container 9.

After circulating the cleaning fluid for a predetermined amount of time, the cleaning fluid is removed from the working fluid container 9. The device is then ready for a further execution of the method for surface working described above.

It will be appreciated that, depending on the application, the cleaning step may be executed after each working step or at irregular or regular intervals, e.g. after a predetermined amount of time or a predetermined number of working steps.

It will be further appreciated that, with other embodiments of the invention, the cleaning fluid does not have to completely replace the working fluid. Rather it is possible that the cleaning fluid sufficiently dilutes the working fluid such that a cleaning effect of sufficient strength is achieved when circulating and withdrawing the solution from the working fluid container.

Second embodiment In the following, a second preferred embodiment of a device 101 for surface working ac- cording to the invention, with which a preferred embodiment of the method according to the invention may be executed, is described with reference to Figure 3.

Figure 3 shows a schematic partially sectional representation of the device 101 for surface working. This device 101 for surface working, apart from the design of the working fluid container 109, does not differ from the one from Figure 1. Thus, identical parts have been given identical reference numerals and only the differences with regard to the working fluid container 109 will be discussed here.

The difference lies within the fact that the working fluid container 109 is not movable to- gether with the second tool device 4 but fixedly mounted to the machine frame 5. The seal- ing connection between the working fluid container 109 and the second tool device 4 is pro- vided by a bellows 109.1 connected to the bottom wall of the working fluid container 109 and the upper end of the second tool drive device 4.2.

This embodiment has the advantage that the mass to be moved during working the body 2 is lower and that no working fluid splashing problems due to displacement movements of the To be able to provide substantially complete clearance of the working fluid container 109 from any fluid received therein, the working fluid supply device 11 is connected to a bottom region of the bellows 109.1 which forms the lowest part of the working fluid container 109.

It will be appreciated that the method for surface working according to the invention as it has been described above in the context of Figure 2 may also be executed with the device 101.

Thus it is here referred only to the above explanations.

Third embodiment In the following, a third preferred embodiment of a device 201 for surface working according to the invention, with which a preferred embodiment of the method according to the invention may be executed, is described with reference to Figure 4.

Figure 4 shows a schematic representation, not to scale, of the device 201 for surface working. As can be seen from Figure 4, the device 201 is a single-disk device with which the upper first surface 202.1 of a body 202 can be worked by means of a tool 203.1 of a tool device 203.

In the embodiment shown, the body 202 is a lens held on a receiving platform 209.2 of a working fluid container 209. The lens 202 is shown with an exaggerated thickness for rea- sons of better visibility. However, it is to be understood that, with the device 201, any other bodies for which a corresponding surface quality is required may also undergo correspond- ing surface working.

The tool device 203 is arranged on a displaceable traverse 205.1 supported at its both ends on a machine frame - not shown. In Figure 4, the traverse 205.1 is shown an operating p0- sition. Similar to the embodiment of Figure 1, the traverse 205.1 and, thus, the tool device 203 may be driven to a displacement position at a distance from the receiving platform 209.2 in which the lens 202 can be inserted into the device 201. For working the lens 202 the trav- erse 205.1 is driven into an operating position. In such an operating position of the traverse 205.1, the tool 203.1 is located above the lens 202.

When the traverse 205.1 is located in such an operating position, the tool 203.1 for the working of the lens 202 is displaced by a tool drive device 203.2 along the tool axis 203.3, i.e. along a second direction 207. 2, in the direction of the lens 202 until the tool 203.1 in an operating position abuts against the lens 202 with a predetermined contact pressure.

The tool 203.1 is a circular-disk-shaped tool. Depending on the application, the tool 203.1 may be a grinding disk, a lapping disk, a honing disk, a polishing disk or a disk for any other type of surface working.

One difference from the first tool device 3 from Figure 1 is that the tool device 203 has a first tool 203.1 with a concave spherical first working surface 203.6. The curvature of the first working surface 203.6 is shown greatly exaggerated in Figure 4 for reasons of better per- ceptibility. In actual applications, working surfaces with a considerably smaller curvature, i.e. a considerably larger radius of curvature, are used. It is hereby possible to work surfaces of a body which deviate from a plane geometry.

A further difference from the first tool device 3 from Figure 1 consists in the fact that the tool device 203 comprises a tool drive device 203.2 which is additionally constructed to tilt the first tool axis 203.3 in the plane of the drawing in the direction of the double arrow 213 about a pivot point lying on the first tool axis 203.3. Furthermore, the first tool drive device 203.2 may additionally be constructed to tilt the tool axis 203.3 in a plane lying transverse to the plane of the drawing about a pivot point lying on the tool axis 203.3, e. g. about a tilt axis perpendicular to the plane of the drawing. As a result, a particularly variable use of the device according to the invention is possible for almost any surfaces to be worked.

It is to be understood that the first working surface, in other variants of the invention, may also have a different geometry. Thus, for example, it may have a convex spherical geometry as is indicated by the dashed contour 214 in Figure 4. Furthermore, it may also have a con- cave or convex conical geometry, as is indicated by the contours 215 and 216 in Figure 4. It is furthermore understood that section-wise combinations of such geometries are also pos- sible. Finally, it is to be understood that, in the case of a convex geometry of the working surface, the tilting movements of the tools are adapted hereto. The pivot point of the pivoting movement then generally lies on the other side of the tool compared to the concave geome- try.

As already mentioned, the curvatures or angles of inclination of the first working surface are shown highly exaggerated in Figure 4 for reasons of better perceptibility. In actual applica- tions working surfaces with a considerably smaller curvature or smaller angles of inclination are used. It is hereby possible also to work surfaces of a body which deviate from a plane geometry.

For working the lens 202, the lens 202 is inserted into the device 201, wherein it then is held on the receiving platform 209.2. At the time of insertion of the lens 202, the tool 203.1 is still located at a sufficient distance from the receiving platform 209.2. The tool device 203 which is then driven to an operating position, such that it abuts against the lens 202 with a pre- defined contact pressure. This contact pressure can be varied during working the lens 202 by the tool drive device 203.2 if the application requires this.

As can be seen from Figure 4, for working the lens 202, the tool 203.1 lies opposite to the receiving platform 209.2. Thus, a working gap 201.1 is formed between them, in which the lens 202 is arranged. The working gap 201.1 mainly extends in a working gap plane which runs perpendicular to the tool axes 3.3 and 4.3.

In the representation of Figure 4, the tool axis 203.3 is in direct alignment with the optical axis of the lens. Anyway, when tilting the tool axis 203.3 it may be favorable or necessary to offset the tool drive device 203.2. In order to achieve this, the tool device 203 may be displaced in the direction of the double arrow 207.1 by means of a corresponding drive inte- grated into the drive device 203.2. Additionally or alternatively, the tool device 203 may be displaced perpendicularly to the drawing plane of Figure 4 for this purpose by a correspond- ing drive integrated into the tool drive device 203.2.

If necessary, some or all of the above displacement movements of the tool device 203 may also take place during the working of the lens 202 with an arbitrarily pre-definable movement profile.

If the application requires it, during working the lens 202, the tool 203. 1 may execute a rotary tool movement about its tool axis 203.3 along a rotary direction 203.7. This rotary tool movement may be effected by the tool drive device 203.2. Again, if necessary, the above rotary tool movement of the tool 203.1 may take place with an arbitrarily predefinable movement profile.

The working fluid container 209 receives a working fluid bath 210.1 of a working fluid 210.

The working fluid bath 210.1 is established by a working fluid supply device 211 connected to the working fluid container 209 and supplying working fluid 210 to the working fluid con- tainer 209.

It will be appreciated that, with other embodiments of the invention, the first tool device 3 shown in Figure 1 may replace the tool device 203 of Figure 4. Similarly, depending on the shape of the surfaces to be worked, the toot devices described in the context of Figure 4 may replace one or both of the first and second toot device 3 and 4 described in the context of Figures 1 and 3.

In the following, a preferred embodiment of the method for surface working according to the invention is described with reference to Figures 4 and 5.

In a first step 212.1, the tool 203.1 and the working fluid container 209 for the working fluid bath 210.1 are provided as a part of the device 201 to provide a configuration as it has been described above in the context of Figure 4.

In a subsequent preparation step 212.2, the configuration as shown in Figure 4 is estab- lished. To this end, in a positioning step 212.3, the lens 202 is placed between the tool 203.1 and the receiving platform 209.2 of the working fluid container 209 such that the tool 203.1, the lens 202 are located within the working fluid container 209. Thereby, the lens 202 is placed and mounted to the receiving platform 209.2. At the time of insertion of the lens 202, the tool 203.1 is still located in a remote displacement position.

fhen, the tool 203.1 is displaced into its operating position, wherein said tool 203.labuts with its working surface 203.6 against the first surface 202.1 of the lens 202, said first surface 202.1 being the surface to be currently worked. Thus, the working surface 203.6 contacts the first surface 202.1 in a first contact area 201.2 extending over the entire first surface 202.1.

In a working fluid bath establishing step 212.4, subsequent to the positioning step ?12.3, the working fluid bath 210.1 is established by the working fluid supply device 211 supplying working fluid 210 to the working fluid container 209. The surface level 210.2 of the working fluid bath 210.1 is adjusted such that, both, the first contact area 201.2 between the tool 203.1 and the lens 202 is completely immersed in the working fluid bath 210.1.

The immersion of the contact area 201.2 provides the advantage that, depending on the height of the surface level 210.2 of the working fluid bath 210.1 above the contact area 201.2, a considerable hydrostatic pressure builds up in the working fluid 210 in the region of the contact area 201.2. This hydrostatic pressure promotes a continuous and non-defective layer of working fluid 210 between the tool 203.1 and the lens 202 over the entire contact area 201. 2. Such a continuous and non-defective layer of working fluid 210 promotes high quality surface working results.

To further promote such a continuous and non-defective layer of working fluid 210 over the entire contact area 201.2, the tool 203.1 is provided with a number of working fluid ducts 203.9. These working fluid ducts 203.9 communicate with the working fluid bath 210.1 and guide working fluid 210 towards different regions of the contact area 201.2.

A further advantage of the complete immersion of the contact area 201.2 lies within the fact that, during working, no local drying of the working fluid either on the surface of the lens 202 or on the working surface of the tool 203.1 may occur.

It will be appreciated that, with other embodiments of the invention, a different number of such working fiuid ducts may be provided. Furthermore, such working fluid ducts may be omitted as well if sufficient working fluid supply to the respective contact area is guaranteed by other circumstances, e.g. a sufficiently high hydrostatic pressure etc. It will be further appreciated that, with other embodiments of the invention, the working fluid bath establishing step may be executed prior to the positioning step. Thus, the body may be placed between the tools after completed establishment of the working fluid bath.

Furthermore, it is also possible to execute the positioning step and the working fluid bath establishing step at least partly simultaneously. For example, the working fluid bath surface level may be raised or lowered only to about the level of receiving platform of the working fluid container. Then, the lens may rapidly and easily be inserted into the device without any substantial resistance of the working fluid. After insertion of the lens, the tool may be posi- tioned while simultaneously raising the working fluid bath surface level. Preferably, the rais- ing working fluid bath floods the first surface of the lens before the tool contacts the first surface. Thus, hereby as well, a continuous and non-defective layer of working fluid over the entire first contact area is promoted.

In a working step 212.5, subsequent to the preparation step 212.2, the first surface 202.1 of the lens 202 is then worked with the tool 203.1 as it has been described above in the context of Figure 4. Preferably, rotary tool movements, tilt movements and displacement movements of the tool 203.1 are superimposed such that an epicycloidal relative movement is produced between the lens 202 and the tool 203.1.

A control device - not shown - controls the respective drive devices connected thereto such that, as a result of the superposition of the tool, tilt and displacement movements, over the entire first surface 202.1 to be worked, a uniform removal of material and, thus, a uniform surface quality are obtained. By the term uniform surface quality should be understood, in the sense of the present application, that the surface roughness over the surface to be worked varies by less than 30% of an average value of the surface roughness.

The control is executed such that the amount of the relative speed between the surface to be worked and the associated working surface is subject to as little variation as possible at every point. Particularly favorable force ratios are hereby achieved during the working which result in a high surface quality. In particular, the control is executed such that the amount of this relative speed is never zero at any point in time. The movements can be superposed for this purpose such that, overall, a sinusoidal relative movement is obtained.

To further promote the continuous and non-defective layer of working fluid 210 over the en- tire contact area 201.2, the contact pressure between the tool 203.1 and the lens 202 is in- termittently temporarily lowered. To this end, the tool 203.1 is intermittently moved back and forth along the first direction 207.1. Thus, the tool 203.1 is shortly moved away from the lens 202. Due to this movement, form the surroundings and via the working fluid ducts 203.9, respectively, fresh working fluid 210 is sucked into the contact area 201.2. After a period of sufficient length the contact pressure is then re-established by re-approaching the tool 203.1 to the lens 202.

The amount by which the tool 203.1 is intermittently retracted from the lens 202 depends on the application, in particular on the viscosity and the wetting properties of the working fluid as well as on the actual and required surface roughness of the lens. In some applications, for example, a few tenths of millimeters may be sufficient.

To prevent sedimentation effects etc. within the working fluid bath 210.1 and to achieve a favorable temperature distribution within the working fluid bath 210.1, during said working step 212.4, a circulation is established in the working fluid bath 210.1. This is achieved by io the working fluid supply device 211 supplying fresh working fluid 210 to the working fluid container 209 and withdrawing used working fluid 210 from the working fluid container 209 at a sufficient rate. Additionally or alternatively, the entire working fluid container may also be rotated, which would also produce a rotary movement of the lens, which might be favorable in some cases. Furthermore, one or more separately driven agitators or the like may be pro- vided as well.

At the end of the working step 212.4, the lens 202 is removed from the device 201. To this end, preferably, the level of the working fluid bath surface 210.2 is lowered so far that the lens 202 may be taken out of the device 201 without inadmissibly high stresses due to its flow resistance. If, for example, any such stresses are to be avoided, the level of the working fluid bath surface 210.2 may be lowered to about the level of the receiving platform 209.2.

Then, the lens 2 may rapidly and easily be take out of the device 201 using a corresponding handling device.

In a cleaning step 212.5, subsequent to the working step 212.4, the working fluid 210 within the working fluid container 209 is substantially completely replaced by a cleaning fluid such as water or the like. The cleaning fluid may be provided by the working fluid supply device 211 as well after the working fluid supply device 211 has withdrawn substantially all the working fluid 210 from the working fluid container 209.

After circulating the cleaning fluid for a predetermined amount of time, the cleaning fluid is withdrawn from the working fluid container 209. The device 201 is then ready for a further execution of the method for surface working described above.

In general, but especially in connection with the variants having a working surface which deviates from a plane geometry, it is to be understood that the working surface must not io necessarily touch or work at a time the entire surface to be worked. Rather, it is also possi- ble that the actual contact area extends only over a part of the surface to be worked.

Furthermore, it will be appreciated that the contact area does not necessarily have to be im- mersed completely within the working fluid bath. It may also be sufficient that only a part of the contact area is immersed within the working fluid bath. The degree of necessary immersion depends for example on the wetting properties of the working fluid and the contact pressure between the tool and the body to be worked. In particular with good wetting proper- ties and/or low contact pressures the entrainment effects of the relative movement between the tool and the body to be worked may be sufficient to guarantee a continuous non- defective working fluid layer over the entire contact area without complete immersion of this contact area.

The invention is described hereinbefore with reference to examples in which, exclusively, rotationally symmetrical surfaces of a body are worked. It is to be understood that, by suita- bly specifying the movement profile of the relative movement between the working surface and the body, non-rotationally symmetrical surfaces of a body, in particular aspherical sur- faces and free-form surfaces, may also be worked using the invention. *****

Claims

- 21 - What is claimed is: 1. A method for surface working of a body

having at least a first surface to be worked, comprising - providing a first tool with a first working surface; - providing a working fluid container; - in a preparation step, establishing a working fluid bath within said working fluid container and positioning at least one of said body, said first tool and said con- tainer such that - said first working surface contacts said first surface in a first contact area and - at least a part of said first contact area is immersed in said working fluid bath; and - in a working step subsequent to said preparation step, working said first surface
2. The method according to claim 1, wherein, in said preparation step, said first contact area is completely immersed in said working fluid bath.
3. The method according to claim 1, wherein, in said working step, said first tool is at least once moved in a direction away from said body to promote inflow of said work- ing fluid into said first contact area.
4. The method according to claim 1, wherein, in said working step, a circulation is es- tablished within said working fluid bath.
5. The method according to claim 4, wherein, in said working step, said circulation within said working fluid bath is established using at least one agitator located within said working fluid container.
6. The method according to claim 1, wherein, in said working step, said working fluid container is moved.
7. The method according to claim 6, wherein, in said working step, said working fluid container is displaced.
8. The method according to claim 6, wherein, in said working step, said working fluid container is moved at least one of in response to a movement of said first tool and in synchronicity with a movement of said first tool.
9. The method according to claim 1, further comprising - providing a second tool with a second working surface for working a second sur- face of said body; - in said preparation step, establishing said working fluid bath and positioning at io least one of said body, said first tool, said second tool and said container such that - said first working surface contacts said first surface in said first contact area and said second working surface contacts said second surface in a second contact area and - at least a part of said first contact area is immersed in said working fluid bath and at least a part of said second contact area and is immersed in said working fluid bath; and - in said working step, working said first surface with said first working surface and working said second surface with said second working surface.
10. The method according to claim 9, wherein - in said preparation step, at least one of said first tool and said second tool is posi- tioned such that said first tool is located opposite to said second tool to form a working gap, said working gap mainly extending in a working gap plane and re- ceiving said body; - in said working step, at least a first relative displacement movement is effected between said body and at least one of said first tool and said second tool in a first direction parallel to said working gap plane.
11. The method according to claim 10, wherein, in said working step, said body is guided, in at least one guide movement, substantially parallel to said working gap plane between said first tool and said second tool.
12. The method according to claim 9, wherein, in said preparation step, said second contact area is completely immersed in said working fluid bath.
13. The method according to claim 1, wherein, in a cleaning step subsequent to said working step, said working fluid within said container is at least partly replaced with a cleaning fluid.
14. The method according to claim 1, wherein it is used for grinding, lapping, honing or polishing said body.
15. The method according to claim 1, wherein said body is an LCD mask.
16. A device for surface working of a body having a first surface to be worked, compris- ing - a first tool with a first working surface, and - a working fluid container adapted to receive a working fluid to form a working fluid bath; - said first tool, for working said first surface, being adapted to contact said first surface with said first working surface in a first contact area; - said working fluid container being arranged such that, when working said first surface, at least a part of said first contact area is immersed in said working fluid bath.
17. The device according to claim 16, wherein said working fluid container is arranged such that said first contact area is completely immersed in said working fluid bath.
18. The device according to claim 16, wherein said first tool comprises at least one working fluid duct guiding said working fluid from said working fluid bath towards said first contact area.
19. The device according to claim 16, wherein - a drive device is provided effecting at least one relative movement between said first tool and said body, - said drive device, when working said first surface, moving said first tool at least once in a direction away from said body to promote inflow of said working fluid into said first contact area.
20. The device according to claim 16, wherein a circulation device is provided, said cir- culation device establishing a circulation within said working fluid bath.
21. The device according to claim 20, wherein said circulation device comprises at least one agitator located within said working fluid container.
22. The device according to claim 16, wherein said working fluid container is movable.
23. The device according to claim 22, wherein said working fluid container is displace- io able.
24. The device according to claim 22, wherein said working fluid container is movable at least one of in response to a movement of said first tool and in synchronicity with a movement of said first tool.
25. The device according to claim 16, further comprising - a second tool with a second working surface for working a second surface of said body; said second tool, for working said second surface, being adapted to contact said second surface with said second working surface in a second contact area; - said working fluid container being arranged such that at least a part of said sec- ond contact area is immersed in said working fluid bath.
26. The device according to claim 25, wherein - said first tool is locatable opposite to said second tool to form a working gap, said working gap mainly extending in a working gap plane and receiving said body; and a displacement mechanism is provided, said displacement mechanism effecting at least a first relative displacement movement between said body and at least one of said first tool and said second tool in a first direction parallel to said working gap plane.
27. The device according to claim 26, wherein, a guide device is provided, said guide device guiding said body substantially parallel to said working gap plane between said first tool and said second tool.
28. The device according to claim 25, wherein said working fluid container is arranged such that said second contact area is completely immersed in said working fluid bath.
29. The device according to claim 16, wherein - a cleaning device is provided, - said cleaning device being connectable to said working fluid container, - said cleaning device being adapted to at least partly replace said working fluid with a cleaning fluid.
30. The device according to claim 16, wherein at least said first tool comprises one of a grinding disk, a lapping disk, a honing disk and a polishing disk.
31. The device according to claim 16, wherein said body is an LCD mask. *****