U.S. patent application number 09/888906 was filed with the patent office on 2002-01-17 for device for machining optical workpieces.
This patent application is currently assigned to Loh Optikmaschinen AG. Invention is credited to Diehl, Joachim, Hanisch, Manfred, Schafer, Holger.
Application Number | 20020006764 09/888906 |
Document ID | / |
Family ID | 7646149 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020006764 |
Kind Code |
A1 |
Hanisch, Manfred ; et
al. |
January 17, 2002 |
Device for machining optical workpieces
Abstract
A very versatile device is proposed for high-precision machining
of optical workpieces, in particular optical lenses, which
comprises a horizontally displaceable gantry with at least one
vertically displaceable tool spindle and a yoke with workpiece
holding means mounted so as to be rotatable about a swivel axis by
means of journals fitted on both sides. For swivelling of the yoke
without gearing and therefore without backlash, a torque motor is
provided concentrically to the swivel axis, which motor is directly
connected actively with one of the journals.
Inventors: |
Hanisch, Manfred;
(Huttenberg, DE) ; Diehl, Joachim; (Giessen,
DE) ; Schafer, Holger; (Weilmunster, DE) |
Correspondence
Address: |
Kirk A. Vander Leest, McAndrews,
Held & Malloy, Ltd.
34th Flr.
500 W. Madison
Chicago
IL
60661
US
|
Assignee: |
Loh Optikmaschinen AG
|
Family ID: |
7646149 |
Appl. No.: |
09/888906 |
Filed: |
June 25, 2001 |
Current U.S.
Class: |
451/1 |
Current CPC
Class: |
Y10T 483/1882 20150115;
B23Q 1/52 20130101; Y10T 483/174 20150115; B23Q 5/28 20130101; Y10T
483/1795 20150115; B23Q 7/045 20130101; B24B 41/062 20130101; B23Q
2039/002 20130101; B24B 13/0031 20130101 |
Class at
Publication: |
451/1 |
International
Class: |
B24B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 2000 |
DE |
100 29 967.9 |
Claims
I CLAIM:
1. A device for machining optical workpieces, in particular optical
lenses, having a frame, which comprises two side walls, which
support a horizontally displaceable gantry with at least one
vertically displaceable tool spindle, there being a space
therebetween which takes the form of a machining area, in which a
yoke comprising a workpiece holding means is provided, which yoke
is mounted on the side walls by means of journals so as to be
rotatable about a pivot axis; wherein, to swivel the yoke, a torque
motor is provided which is attached to a side wall of the frame
concentrically to the swivel axis and is connected actively with
the associated journal of the yoke.
2. A device according to claim 1, wherein counterweights are
attached to the journals of the yoke, which counterweights generate
a torque at the journals, which counteracts the torque generated by
the yoke.
3. A device according to claim 2, wherein the counterweights are
arranged on the sides of the side walls of the frame remote from
the machining area.
4. A device according to claim 1, wherein the yoke may be locked in
its particular swivel position by means of a frictional or
interlocking brake, which is attached to the opposite side wall
from the torque motor.
5. A device according to claim 1, wherein the journal of the yoke
actively connected with the torque motor is mounted in the
corresponding side wall of the frame with a swivel bearing on each
side of the torque motor and wherein the swivel bearing lying
nearest the machining area takes the form of a fixed bearing.
6. A device according to claim 1, wherein the swivelling movement
of the yoke is controlled on the basis of signals, which are
detected by means of a rotary transducer arranged on the swivel
axis of the yoke.
7. A device according to claim 1, wherein a horizontal slide for
two tool spindles is provided on the gantry, which slide is
displaceable in the direction perpendicular to the direction of
movement of the gantry and which tool spindles are displaced
independently of one another in the vertical direction, in
particular for optional rough or fine machining of the
workpiece.
8. A device according to claim 1 and comprising a workpiece loading
means, which is displaced in the vertical direction together with
the tool spindle.
9. A device according to claims 1, wherein the workpiece holding
means comprises two workpiece spindles, the axes of rotation of
which lie in a plane with the swivel axis of the yoke.
10. A device according to claim 1, wherein a tool changer is
arranged between the side walls of the frame, which tool changer is
displaceable parallel to the gantry.
11. A device according to claim 1, wherein the frame consists of
polymer concrete.
12. A device for machining optical workpieces, in particular
optical lenses, having a frame, which comprises two side walls,
which support a horizontally displaceable gantry with at least one
vertically displaceable tool spindle, there being a space
therebetween which takes the form of a machining area, in which a
yoke comprising a workpiece holding means is provided, which yoke
is mounted on the side walls by means of journals so as to be
rotatable about a pivot axis; wherein a horizontal slide for two
tool spindles is provided on the gantry, which slide is
displaceable in the direction perpendicular to the direction of
movement of the gantry and which tool spindles are displaced
independently of one another in the vertical direction, in
particular for optional rough or fine machining of the
workpiece.
13. A device according to claim 12, and comprising a workpiece
loading means, which is displaced in the vertical direction
together with the tool spindle.
14. A device for machining optical workpieces, in particular
optical lenses, having a frame, which comprises two side walls,
which support a horizontally displaceable gantry with at least one
vertically displaceable tool spindle, there being a space
therebetween which takes the form of a machining area, in which a
yoke comprising a workpiece holding means is provided, which yoke
is mounted on the side walls by means of journals so as to be
rotatable about a pivot axis; wherein the workpiece holding means
comprises two workpiece spindles, the axes of rotation of which lie
in a plane with the swivel axis of the yoke.
15. A device according to claim 12, wherein a tool changer is
arranged between the side walls of the frame, which tool changer is
displaceable parallel to the gantry.
16. A device according to claim 14, wherein a tool changer is
arranged between the side walls of the frame, which tool changer is
displaceable parallel to the gantry.
17. A device according to claim 12, wherein the frame consists of
polymer concrete.
18. A device according to claim 14, wherein the frame consists of
polymer concrete.
Description
BRIEF DESCRIPTION OF THE PRIOR ART
[0001] The present invention relates to a device for machining
optical workpieces, in particular optical lenses, having a frame,
which comprises two side walls, which support a horizontally
displaceable gantry with at least one vertically displaceable tool
spindle and the space between which takes the form of a machining
area, in which a yoke comprising a workpiece holding means is
provided, which yoke is mounted on the side walls by means of
journals so as to be rotatable about a swivel axis.
[0002] Such devices are known from metal working using machine
tools, in particular drilling and milling machines (EP 0 712 682
B1). These machines are constructed according to the "gantry"
design, i.e. they have a gantry with a cross slide and a vertically
disposed tool spindle, which may be displaced horizontally and
vertically along two axes. One or more workpiece holders may be
arranged in a swivellable yoke arranged beneath the tool spindle.
The workpieces are either operated rotationally by means of a
spinning table or are merely attached stationarily in the yoke.
[0003] It is common to all known machines in which a swivellable
yoke is used for the swivelling motion always to be generated by a
servo motor via appropriate gearing. In a known machine (DE 36 24
284 C2, FIG. 4), a reducing gear is used to swivel the yoke, a
rotary transmission leadthrough with a drive fitted outside the
yoke being additionally provided for rotary drive of the
workpieces. However, this multi-component, mechanically complex
gearing system inevitably exhibits backlash, which has a very
disadvantageous effect on the repeatability of the angle to be set.
However, angular adjustment precision is very important, in
particular in the case of grinding spherical optical surfaces.
[0004] The object of the invention is to provide a device for
machining optical workpieces which structurally follows the gantry
design, but allows high-precision cutting machining even of large
optical components with low mechanical complexity even in the event
of high process forces and/or varying temperature influences.
SUMMARY OF THE INVENTION
[0005] According to the present invention, there is provided a
device for machining optical workpieces, in particular optical
lenses, having a frame, which comprises two side walls, which
support a horizontally displaceable gantry with at least one
vertically displaceable tool spindle, there being a space
therebetween which takes the form of a machining area, in which a
yoke comprising a workpiece holding means is provided, which yoke
is mounted on the side walls by means of journals so as to be
rotatable about a pivot axis; wherein, to swivel the yoke, a torque
motor is provided which is attached to a side wall of the frame
concentrically to the swivel axis and is connected actively with
the associated journal of the yoke.
[0006] Taking as basis the above-stated prior art (EP 0 712 682
B1), claim 1 provides, while avoiding any gear arrangements, a
simply constructed device in which no backlash may occur and which
therefore allows the achievement of highly and reproducibly precise
yoke swivelling movements and thus angular adjustment. The torque
motor transmits the swivelling movements directly to the yoke.
[0007] If the yoke weight is compensated by counterweights, the
torque motor has only to apply a very slight torque in order to
bring the entire yoke, with the workpiece holding means/workpiece
spindles and the workpieces, into the respective angular position.
Only low motor power has therefore to be provided, which is
favourable from the point of view of energy consumption and also
does not cause excessive heating, which would be detrimental to
adjusting and machining precision.
[0008] If the counterweights are arranged relative to the side
walls of the frame, a narrow, high rigidity yoke is achieved, which
in turn benefits machining precision.
[0009] The attachment, of a frictionally or interlockingly
operating brake allows reliable locking of the yoke in any set
angular position, whereby the range of possible geometries which
may be produced by the device may be extended. A suitable,
pneumatically or hydraulically actuated device may be provided to
unlock the brake.
[0010] The devices may be such that the journal of the yoke
actively connected with the torque motor is mounted in the
corresponding side wall of the frame with a swivel bearing on each
side of the torque motor and wherein the swivel bearing lying
nearest the machining area takes the form of a fixed bearing.
[0011] This is an advantageous configuration of the swivel bearing
arrangement for the yoke on the bearing journal connected actively
with the torque motor. This ensures that, even in the event of
heating of the yoke, no axial displacement of the yoke and thus of
the workpiece holding means/workpiece spindles relative to the tool
spindle may occur as a result of thermal expansion. Possible
thermal expansion in the journal area is thus unable to spread into
the machining area of the device, a fact which is conducive to the
achievement of high machining precision. However, this
thermosymmetrical construction of the device not only provides
considerable advantages in the thermal respect but also with regard
to the stability of the machine structure relative to the
deformation tendencies caused by process forces. The construction
according to the invention of the device also allows the area of
the swivel bearings to be specifically temperature-controlled by
water cooling, in particular in the area of the torque motor.
[0012] The swivelling movements performed by the yoke may be
detected and controlled by a high-resolution rotary transducer.
This direct detection of the angle of rotation allows high control
quality and thus likewise serves in achieving the desired high
machining precision.
[0013] A horizontal slide for two tool spindles is preferably
provided on the horizontally displaceable gantry, which two
spindles may be displaced independently of one another in the
vertical direction in particular for optional rough or fine
machining of the workpiece. The mutually independent
displaceability of the two tool spindles is beneficial to the
desired very narrow yoke construction, because the tool spindle not
required at any one time may be moved upwards out of collision
range. The narrower the yoke, the more rigidly it may be
constructed, to allow high machining precision. However, this
construction also allows simple cross-grinding adjustment without
any additional adjusting means via the available CNC movement axis
of the horizontal slide.
[0014] A workpiece loading means may be provided, which is
vertically displaceable together with the tool spindle and shares
in the CNC- controlled movements of the relevant tool spindle and
therefore advantageously does not require any additional CNC
axes.
[0015] The workpiece holding means can comprise two workpiece
spindles with the axes of rotation lying in a plane with the swivel
axis of the yoke. Of particular advantage is the position of the
axes of rotation of the two tool spindles relative to the swivel
axis of the yoke, because the centre of the workpiece thereby
substantially remains in the area of the swivel axis. The very
short lever ratios thereby allowed offer considerable advantages
for the precision of angular positioning.
[0016] To reduce device idle times a tool changer may be arranged
between the side walls of the frame, which tool changer may be
displaced parallel to the gantry and with which a replacement tool
may be brought very rapidly into the machining area of the
device.
[0017] Given the aim of achieving as high as possible a degree of
machining precision, it is advantageous for the frame to consist of
polymer concrete, since this allows better vibration damping, less
influencing of the temperature and active temperature control of
the machine frame.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Further details of the invention are described in more
detail below with reference to the drawings, which schematically
represent an exemplary embodiment and in which:
[0019] FIG. 1 is a perspective view of the device from the
front/above,
[0020] FIG. 2 is a perspective view, corresponding to the view
according to FIG. 1, from the front/above, but without the gantry
and the horizontal slide,
[0021] FIG. 3 is a front view of the device,
[0022] FIG. 4 shows a section through the device along the section
line VI-VI in FIG. 3,
[0023] FIG. 5 is a plan view of the device and
[0024] FIG. 6 is a broken-away and partially broken-open
longitudinal section substantially through the yoke and the
associated parts.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] The device revealed in the drawings takes the form of a
CNC-controlled grinding machine in particular for surface and
edge-grinding of optical lenses L. The device has a frame 1 moulded
from polymer concrete with two horizontally spaced side walls 2, on
the upper surfaces of which there are attached guide rails 3
extending horizontally and parallel to one another. A gantry 4
displaceable horizontally in both directions of a Y-axis is mounted
slidably on the two guide rails 3. As is clear from FIG. 4, sliding
of the gantry 4 is effected by means of a roller ball spindle 5
attached stationarily to the frame 1 and a hollow shaft servo motor
6 engaging non-interlockingly therewith and fitted in the gantry 4.
The space between the side walls 2 forms a machining area 7, in
which tools act on the lenses L in a manner still to be described.
Two tool spindles 8 displaceable vertically in both directions of a
Z-axis are provided on the gantry 4 likewise in a manner still to
be described.
[0026] In the machining area 7 there is located a U-shaped yoke 9,
which carries on its web portion 10 a workpiece holding means 11,
which will be described in greater detail. Journals 13 pointing
outwards and arranged in mutual coaxial alignment are attached to
each of the branches 12 of the yoke 9, as is shown best by FIG. 6.
These journals 13 serve to mount the yoke 9 on the side walls 2
rotatably about a swivel axis A. To swivel the yoke 9 about the
swivel axis A, a torque motor 14 is provided which is attached to a
side wall 2 of the frame 1 concentrically to the swivel axis A and
is connected actively with the associated journal 13 of the yoke 9,
i.e. may move this journal 13 and thus the entire yoke 9 with the
workpiece holding means 11 in both directions of rotation
non-interlockingly and rotationally in accordance with control
signals. To this end, the torque motor 14 has, according to FIG. 6,
a stator S mounted non-rotatably in the right-hand side wall 2 and
a rotor R fitted non-rotatably on the journal 13 of the yoke 9. It
is clear that the torque motor 14 is actively connected directly,
i.e. without gearing, with the associated journal 13 of the yoke 9.
Like the Y-axis and the Z-axis, the swivel axis A is also
CNC-controlled.
[0027] Counterweights 15 are attached, non-rotatably relative to
the yoke 9, to both journals 13 of the yoke 9 on the sides remote
from the machining area, i.e. outside the side walls 2 of the frame
1. These generate a torque at the journals 13, which counteracts
the torque generated by the yoke 9 and the holding means 11,
substantially compensating the latter.
[0028] For certain machining processes, the yoke 9 may preferably
be locked in its particular swivel position by means of a
frictional or interlocking brake 16, which may be spring
pre-tensioned. In the exemplary embodiment illustrated, the brake
16 is attached to the opposite side wall 2 from the torque motor
14, as revealed by FIG. 6. To unlock the brake, a suitable
pneumatically or hydraulically actuated device (not shown) is
provided.
[0029] As FIG. 6 also shows, the journal 13 of the yoke 9 connected
actively with the torque motor 14 is mounted rotatably in the
corresponding side wall 2 of the frame 1 with a swivel bearing on
each side of the torque motor 14. On the motor side, the swivel
bearing 17 nearest the machining area 7 takes the form of a fixed
bearing and the outer swivel bearing 18 takes the form of a movable
bearing. The other journal 13 of the yoke 9 is mounted rotatably in
the other side wall 2 with a swivel bearing 18 in the form of a
movable bearing on each side of the brake 16.
[0030] The swivel movements of the yoke 9 may be controlled on the
basis of signals, which may be detected by means of a
high-resolution rotary transducer 19, which is arranged on the
swivel axis A of the yoke 9, in the example illustrated externally
on the motor-side journal 13 of the yoke 9 (FIG. 6).
[0031] It is clear from FIGS. 1, 4 and 5 that a horizontal slide 20
may be displaced on the gantry 4 on mutually parallel guide rails
21 attached horizontally on the gantry 4. The gantry 4 and the
horizontal slide 20 form a cross-slide arrangement, in which the
horizontal slide 20 may be displaced in both directions of an
X-axis, which extends perpendicularly to the Y-axis of the gantry
4. The movements on the X-axis are also CNC-controlled.
[0032] Two tool spindles 8 are provided on the horizontal slide 20,
which spindles 8 may be displaced vertically along the Z-axis
independently of one another in particular for optional rough or
fine machining of the workpiece.
[0033] A workpiece loading means visible in FIGS. 1, 4 and 5, which
allows automatic workpiece change-over, consists of a cylinder 22
attached to the spindle head of a tool spindle 8 and a loading arm
23 with suction cup 24, which loading arm 23 may be moved up and
down and swivelled by the cylinder 22. The loading means may be
displaced vertically along the Z-axis together with the relevant
tool spindle 8.
[0034] The loading means may, for example, transport lenses L from
a pallet store 25 or the like to the respective workpiece spindle
26, of which the holding means 11 on the web part 10 of the yoke 9
comprises two (FIG. 6). It is additionally possible to insert the
lens into a centring station 27 and also into a reversing station
28 by means of the loading means. The lens is removed in the
reversed position from the reversing station 28 and inserted into a
workpiece receptacle 29 attached to the workpiece spindle 26 for
machining of its rear.
[0035] Of particular advantage in this design of the device is that
no additional CNC-controlled axes are required for the movements of
the loading arm 23. The two horizontal X and Y CNC axes thus allow
fully automated workpiece change-over with little additional effort
with the aid of the additional pneumatic cylinder 22.
[0036] Since the axes of rotation of the two workpiece spindles 26
lie in a plane with the swivel axis A of the yoke 9, the centre of
the workpiece remains substantially in the area of the swivel axis
A.
[0037] A tool changer 30 is arranged between the side walls 2 of
the frame, which tool changer 30 may be displaced parallel to the
guide rails 3 of the gantry 4. The tool changer 30 may also be
displaced on guide rails 31 which are attached to the frame 1
parallel to the guide rails 3 of the gantry 4, as is clearest from
FIG. 2 and FIG. 4 together. Sliding drive of the tool changer 30
proceeds by means of a hydraulic or pneumatic cylinder/piston
arrangement 32 acting thereon, which is arranged in a recess 33 in
the frame 1. A replacement tool may be moved into the machining
area 7 very quickly by means of the tool changer 30. A carrousel
store 34 belonging to the tool changer 30 may be appropriately
indexed for the purpose of tool change-over, wherein the horizontal
slide 20 with the respective tool spindle 8 may be positioned above
the replacement tool or the tool to be replaced in the carrousel
store 34. This arrangement allows very rapid tool change-over,
because no long horizontal paths have to be travelled with the
heavy cross-slide arrangement consisting of gantry 4 and horizontal
slide 20. The tool changer 30 allows even very complex workpieces
with different geometries to be machined with relatively little
effort.
[0038] The above description is of an exemplary embodiment having
two tool spindles 8, but it is also possible to use just one tool
spindle 8 for example to machine very large workpieces. The same
applies to the number of workpiece spindles 26, i.e. the fitting of
just one workpiece spindle 26 on the yoke 9 is possible, e.g. for
machining large lenses with a diameter of 300 mm and more. To
machine complex flat optical or hybrid optical components, it is
possible, for example, for the workpiece to be highly precisely
positioned using this one workpiece spindle 26, while individual
flat surfaces are produced by means of cup or disk grinding tools
or other tools. The use of disk milling cutters or cutter heads in
the "flycutting" process is also possible, in order for example to
produce inserts for injection moulds of metal by means of the
device. Apart from the machining of such casting moulds or glass
lenses and moulds, the device may also be used to machine polishing
compression moulds of silicon carbide or ceramic drop-plate-type
moulding substrates.
[0039] Due to the kinematic conditions of the device according to
the invention, it is possible, in addition to spherical and flat
optics, to machine aspheres, toroidal surfaces and also aspheres
which are not rotationally symmetrical (atoroidal or progressive
surfaces) as well as freeform surfaces. The device may operate both
with cup grinding tools and in single point mode (as described for
example in DE 195 29 786 C1 in the name of the applicant). Disk
grinding tools may operate according to the principle of rotary
circumferential cross grinding or longitudinal grinding.
[0040] A very versatile device is proposed for high-precision
machining of optical workpieces, in particular optical lenses,
which comprises a horizontally displaceable (Y-axis) gantry with at
least one vertically displaceable (Z-axis) tool spindle and a yoke
with workpiece holding means mounted so as to be rotatable about a
swivel axis A by means of journals fitted on both sides. For
swivelling of the yoke without gearing and therefore without
backlash, a torque motor is provided concentrically to the swivel
axis A, which motor is directly connected actively with one of the
journals.
* * * * *