U.S. patent application number 11/480213 was filed with the patent office on 2007-03-22 for method and tool head for machining optically active surfaces, particularly surfaces of progressive spectacle lenses, which are symmetrical in pairs.
Invention is credited to Andreas Bielke, Wolf Krause.
Application Number | 20070062015 11/480213 |
Document ID | / |
Family ID | 34745045 |
Filed Date | 2007-03-22 |
United States Patent
Application |
20070062015 |
Kind Code |
A1 |
Krause; Wolf ; et
al. |
March 22, 2007 |
Method and tool head for machining optically active surfaces,
particularly surfaces of progressive spectacle lenses, which are
symmetrical in pairs
Abstract
A method and a tool head are provided for the chip-removingly
machining of pairwise symmetrical, optically effective surfaces, in
particular of surfaces of progressive power spectacle lenses. The
spectacle lenses are rotated about a first axis and are displaced
along the axis. Further, a chip-removing tool is provided being
positioned and being adapted to be fed-in, such that a cutting edge
of the tool is guided over the surface along a spiralled path and
along an elevation function given by the shape of the spectacle
lens, when the latter is rotated about the first axis. For
machining right side spectacle lenses and left side spectacle
lenses, the right side spectacle lenses are rotated about the first
axis in a first rotational direction, and the left side spectacle
lenses are rotated about the first axis in a second rotational
direction opposite the first rotational direction. The tool head
comprises chucking means defining an axis of the tool head, and a
tool carrier section having at least two lathing tools arranged at
a periphery thereof. The one lathing tool of the pair is oriented
in the one circumferential direction of the periphery, and the
other lathing tool of the pair is oriented in the opposite
circumferential direction of the periphery. At least one,
preferably all of the lathing tools are provided with adjustment
means allowing an adjustment of a point of engagement of the
lathing cutting edge.
Inventors: |
Krause; Wolf; (Essingen,
DE) ; Bielke; Andreas; (Steinheim, DE) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
34745045 |
Appl. No.: |
11/480213 |
Filed: |
June 30, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP05/00412 |
Jan 18, 2005 |
|
|
|
11480213 |
Jun 30, 2006 |
|
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Current U.S.
Class: |
29/27C ;
82/1.11 |
Current CPC
Class: |
Y10T 29/5114 20150115;
B23B 2215/40 20130101; Y10T 29/49996 20150115; B24B 13/01 20130101;
Y10T 82/10 20150115; B23B 29/248 20130101; B24B 13/06 20130101;
Y10T 409/303808 20150115; Y10T 29/5168 20150115; B23C 5/006
20130101; B23C 3/16 20130101 |
Class at
Publication: |
029/027.00C ;
082/001.11 |
International
Class: |
B23B 3/00 20060101
B23B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2004 |
DE |
10 2004 003 583.0 |
Claims
1. A method for machining pairwise symmetrical, optically effective
surfaces by chip-removing, wherein said surfaces are rotated about
a first axis and are displaced along said axis, a chip-removing
tool being provided, said tool being positioned and being adapted
to be fed in, such that a cutting edge of said tool is guided over
said surface along a spiralled path and along an elevation function
given by said shape of said spectacle lens, when said spectacle
lens is rotated about said first axis, wherein for machining right
side spectacle lenses and left side spectacle lenses, said right
side spectacle lenses are rotated about said first axis in a first
rotational direction, and said left side spectacle lenses are
rotated about said first axis in a second rotational direction
opposite said first rotational direction.
2. The method of claim 1, wherein said optically effective surfaces
are surfaces of progressive power spectacle lenses.
3. The method of claim 2, wherein for machining right side
spectacle lenses and left side spectacle lenses of same optical
power, said spectacle lenses are displaced along said first axis in
a same manner.
4. The method of claim 2, wherein said chip-removing is executed by
lathing.
5. The method of claim 4, wherein prior to said lathing said
spectacle lenses are pre-machined by milling.
6. The method of claims 4, wherein a first lathing tool is used
during said lathing of said right side spectacle lens and a second
lathing tool is used during said lathing of said left side
spectacle lens, said lathing tools being oppositely oriented with
respect to said direction of said spiralled path.
7. The method of claim 6, wherein said lathing tools have a lathing
cutting edge and are adjusted with respect to a position of said
lathing cutting edge.
8. A tool head for machining pairwise symmetrical, optically
effective surfaces by chip-removing, comprising chucking means
defining an axis of said tool head, and a tool carrier section
having at least two lathing tools arranged at a periphery thereof,
said lathing tools being each provided with a lathing cutting edge,
wherein at least one of said lathing tools is provided with
adjustment means allowing an adjustment of a point of engagement of
said lathing cutting edge with said surface.
9. The tool head of claim 8, being adapted to machine surfaces of
progressive power spectacle lenses.
10. The tool head of claim 8, wherein preferably all of said
lathing tools are provided with said adjustment means.
11. The tool head of claim 8, wherein said adjustment means allow
an adjustment of said point of engagement in a direction to said
axis.
12. The tool head of claim 8, wherein said adjustment means allow
an adjustment of said point of engagement in a direction
perpendicular to said axis.
13. The tool head of claim 8, wherein, further, milling tools are
arranged at said periphery of said tool carrier section.
14. The tool head of claim 9, wherein said milling tools have
milling cutting edges with a point of engagement with said surface
located on a cutting circle extending about said axis, said points
of engagement of said lathing cutting edges being located within
said cutting circle at a predetermined distance thereto.
15. A tool head for machining pairwise symmetrical, optically
effective surfaces by chip-removing, comprising chucking means
defining an axis of said tool head, and a tool carrier section
having at least two lathing tools arranged at a periphery thereof,
wherein at least one pair of lathing tools is provided, one lathing
tool of said pair being oriented in one circumferential direction
of said periphery, and another lathing tool of said pair being
oriented in an opposite circumferential direction of said
periphery.
16. The tool head of claim 15 being adapted to machine surfaces of
progressive power spectacle lenses.
17. The tool head of claim 15, wherein two pairs of lathing tools
are provided.
18. The tool head of claim 15, wherein, further, milling tools are
arranged at said periphery of said tool carrier section.
19. The tool head of claim 18, wherein said milling tools have
milling cutting edges with a point of engagement with said surface
located on a cutting circle extending about said axis, said points
of engagement of said lathing cutting edges being located within
said cutting circle at a predetermined distance thereto.
Description
CROSSREFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of international patent
application PCT/EP2005/000412 filed on Jan. 18, 2005 and published
in German language as WO 2005/068120, which international patent
application claims priority from German patent application 10 2004
003 583.0, filed Jan. 19, 2004.
FIELD OF THE INVENTION
[0002] The invention, generally, is related to the field of
manufacturing optically effective surfaces of, for example, lenses
and mirrors and to tool heads used for carrying out the method.
[0003] More specifically, the invention is related to the field of
machining pairwise symmetrical, optically effective surfaces by
chip-removing, in particular by lathing and/or milling and/or
grinding.
[0004] Still more specifically, the invention is related to a
method for the chip-removingly machining of pairwise symmetrical,
optically effective surfaces, in particular of surfaces of
progressive power spectacle lenses, wherein the spectacle lenses
are rotated about a first axis and are displaced along the axis, a
chip-removing tool being provided, the tool being positioned and
being adapted to be fed in, such that a cutting edge of the tool is
guided over the surface along a spiralled path and along an
elevation function given by the shape of the spectacle lens, when
the spectacle lens is rotated about the first axis.
[0005] The invention, further, is related to a tool head for the
chip-removingly machining of pairwise symmetrical, optically
effective surfaces, in particular of surfaces of progressive power
spectacle lenses, comprising chucking means defining an axis of the
tool head, and a tool carrier section having at least two lathing
tools arranged at a periphery thereof, being each provided with a
lathing cutting edge.
[0006] Still more specifically, the invention, insofar, is related
to a tool head for the chip-removingly machining of pairwise
symmetrical, optically effective surfaces, in particular of
surfaces of progressive power spectacle lenses, comprising chucking
means defining an axis of the tool head, and a tool carrier section
having at least two lathing tools arranged at a periphery
thereof.
BACKGROUND OF THE INVENTION
[0007] In the context of the present application the term "pairwise
symmetrical, optically effective surfaces" encompasses all such
surfaces, i.e. not only the progressive power spectacle lenses
already mentioned as an example. Instead, the invention may be used
for all applications on optically effective surfaces being used in
pairs, for example for lenses and mirrors as are used in binocular
applications, e.g. telescopes, microscopes, and the like.
[0008] U.S. Pat. No. 6,991,525 describes a method and a tool head
of the type specified at the outset. This prior art method uses a
tool head having an essentially tapered main body. The main body
axis coincides with the tool head axis of rotation. The larger
terminal plane of the main body lies at the free end of the tool
head. Two equal lathing tools being offset relative to one another
by 180.degree. are located at the periphery of the larger terminal
plane and are equally oriented in a circumferential direction of
the periphery. Further, there are eight milling tools distributed
along the periphery. The cutting edges of all these tools are
rigidly bolted at their respective positions. No means for
adjusting the position of the cutting edges are provided.
[0009] The spectacle lens to be machined is positioned in a holder
being chucked in a work piece spindle. The work piece spindle
rotates the spectacle lens about a first axis and is further
adapted to be displaced along that first axis. The tool head is
chucked in a tool spindle having a second axis which is inclined
relative to the first axis of the work piece spindle. The tool is
adapted to be rotated about the second axis at a high rotary speed.
The tool spindle, further, is adapted to be displaced along a third
axis extending perpendicular to the first axis.
[0010] For machining the spectacle lens one proceeds in two steps.
Firstly, in a first operating step the substantially major portion
of the overmeasure of a spectacle lens blank is removed by milling.
Secondly, in a second operating step the fine machining and the
shaping of the surface is effected so as to generate the desired
optical plane, for example a prescription plane. Subsequently, the
spectacle lens may be polished or otherwise coated, as known per
se.
[0011] For effecting the first operational step, the tool head is
brought into rotation about the second axis. By displacing the
spectacle lens along the first axis and by displacing the work
piece spindle along the third axis, a point of engagement of the
milling tool at the periphery of the surface to be machined is set.
The spectacle lens is rotated about the first axis in a
predetermined direction of rotation, and the tool head is displaced
continuously along the third axis, such that the point of
engagement moves along a narrow spiralled path on the surface
towards a central point. The material is, thereby, removed by
milling. By superimposing a movement of the spectacle lens along
the first axis, a coarse convex or concave shaping may be effected
simultaneously, which, however, is not the exact shaping of the
desired free-form surface.
[0012] For the second operational step the tool head is rotated
only once about a finite angle until a point of engagement of a
lathing tool is at a desired peripheral position, whereafter it is
rotated no more. The spectacle lens is now again rotated about the
first axis in a predetermined direction of rotation, and the tool
head is continuously displaced along the third axis such that the
point of engagement again moves along a narrow spiralled path on
the surface towards the center point thereof. The material is now
removed by lathing. In this second operational step an elevation
function along the spiralled path is set by superimposing a
movement of the spectacle lens along the first axis. The elevation
function corresponds to the desired free-form shape of the optical
surface.
[0013] Now, during the manufacture of such spectacle lenses, the
free-form surfaces for the right side and for the left side lens of
equal optical powers are essentially mirror-symmetrical. In
conventional manufacturing processes, the machining of all
spectacle lenses, i.e. the right side lenses as well as the left
hand lenses, is effected within the same apparatus as described
before, and is effected in the same manner, i.e. always along the
same direction of rotation of the spectacle lens about the first
axis.
[0014] During the chip-removingly machining of spectacle lenses one
is always confronted with inherent form defects because the
machining system, consisting of spindles, mounts, etc., is elastic,
and, therefore, due to inertial forces exerted by moved elements,
positioning errors occur during changes in position. This holds
true in particular for the setting of the elevation function. The
spectacle lenses, namely, are rotated in practice at rotational
speeds within such high rotational speed ranges (typically several
100 rpm) about the first axis that non-negligible form defects
occur due to insufficient dynamic behaviour when the spectacle lens
is simultaneously displaced along the first axis.
[0015] The machining system is non-symmetrical in the meaning that
like form defects would occur with inverted sign when the same
elevation function is run through in the opposite direction. During
the conventional machining of spectacle lenses, as described above,
this results in practice in unequal form defects for the right side
and the left side spectacle lenses. This must be prevented by
substantial correctional measures, i.e. by shaping lead values that
are complicated to compute.
[0016] The prior art tool, further, has the disadvantage that due
to the rigid arrangement of the tools on the tool head, one cannot
produce defined conditions of engagement.
SUMMARY OF THE INVENTION
[0017] It is, therefore, an object underlying the invention, to
improve a method and a tool head of the type specified at the
outset such that the above-mentioned disadvantages are avoided. In
particular, it shall become possible to manufacture right side and
left side spectacle lenses more easily and without the inherently
different form defects in right side and left side spectacle lenses
as occur in the prior art due to the mirror-symmetrical elevation
function of the free-form surfaces.
[0018] According to the method specified at the outset, this object
is achieved in that for machining right side spectacle lenses and
left side spectacle lenses, the right side spectacle lenses are
rotated about the first axis in a first rotational direction, and
the left side spectacle lenses are rotated about the first axis in
a second rotational direction opposite the first rotational
direction.
[0019] According to the tool head of the type specified first at
the outset, this object is achieved in that at least one,
preferably all of the lathing tools are provided with adjustment
means allowing an adjustment of a point of engagement of the
lathing cutting edge.
[0020] According to the tool head of the type specified second at
the outset, this object is achieved in that at least one pair of
lathing tools is provided, and that the one lathing tool of the
pair is oriented in one circumferential direction of the periphery,
and the other lathing tool of the pair is oriented in the opposite
circumferential direction of the periphery.
[0021] The object underlying the invention is, thus, entirely
solved.
[0022] If, namely, the direction of rotation about the first axis
during the machining of the right side and of the left side
spectacle lens is set oppositely, then the cutting edge of the tool
follows the elevation function in the same direction, such that the
form defects are equal in both cases, and, therefore, need to be
corrected only one time, i.e. by a same shaping lead value for both
spectacle lenses.
[0023] The provision of adjustment means has the advantage that the
conditions for engagement are defined for several cutting edges,
when, one the one hand, one machines with the first lathing tool
for right side spectacle lenses in the first direction of rotation,
and, on the other hand at a different moment in time one machines
with the second lathing tool for left side spectacle lenses in the
opposite direction of rotation.
[0024] The provision of pairs of lathing tools with opposite
orientation has the advantage that by simply rotating the tool head
about a certain angle one may at one time machine right side
spectacle lenses and at another time left side spectacle lenses in
opposite directions of rotation.
[0025] In a preferred embodiment of the invention, for the
machining of right side spectacle lenses and of left side spectacle
lenses of same optical power, the spectacle lenses are displaced
along the first axis in the same manner.
[0026] This measure has the advantage that the sets of data for the
elevation functions must be generated only once.
[0027] It is particularly preferred when, as is known per se, the
chip-removing is executed by lathing, and when, preferably,
further, also in a manner known per se, the spectacle lenses are
pre-machined by milling prior to the lathing.
[0028] This measure has the advantage that well-known manufacturing
processes and manufacturing installations may be used.
[0029] In another preferred embodiment of the invention a first
lathing tool is used during the lathing of the right side spectacle
lens and a second lathing tool is used during the lathing of the
left side spectacle lens, wherein the lathing tools are oppositely
oriented with respect to the direction of the spiralled path.
[0030] This measure has the advantage that the inventive method may
be used with particularly simple tools.
[0031] In that case it is particularly preferred when the lathing
tools are adjusted with respect to the position of their lathing
cutting edge.
[0032] In a preferred embodiment of the inventive tool head, the
adjustment means allow an adjustment of the point of engagement in
the direction to the axis.
[0033] This measure has the advantage that all points of engagement
may be laid into the same radial plane.
[0034] Further, the adjustment means may allow an adjustment of the
point of engagement in a direction perpendicular to the axis.
[0035] In other embodiments of the invention, two pairs of lathing
tools may be provided.
[0036] This measure, on the one hand, has the advantage that for
different pairs of lathing tools different lenses may be machined
with the same tool head, e.g. lenses of a first material may be
machined with the first pair, and lenses of a second material may
be machined with the second pair. On the other hand the pairs of
lathing tools may be of the same design, wherein the second pair is
used when the first pair is worn out or damaged, thus avoiding the
need to change the tool head at that instance.
[0037] In a manner known per se, milling tools may be arranged at
the periphery of the tool carrier section. In particular, the
milling tools may have milling cutting edges with a point of
engagement located on a cutting circle extending about the axis,
and points of engagement of the lathing cutting edges are located
within the cutting circle at a predetermined distance thereto.
[0038] Further advantages will become apparent from the description
and the enclosed drawing.
[0039] It goes without saying that the features mentioned above and
those that will be explained hereinafter may not only be used in
the particularly given combination, but also in other combinations,
without leaving the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Embodiments of the invention are shown in the drawing and
will be explained in further detail throughout the subsequent
description.
[0041] FIG. 1 shows an apparatus for machining spectacle lenses
according to the prior art;
[0042] FIG. 2A shows an elevation function for one turn for a right
side spectacle lens to be machined according to the prior art;
[0043] FIG. 2B shows an elevation function for one turn for a left
side spectacle lens having the same optical power as that in FIG.
2A to be machined according to the prior art;
[0044] FIG. 3A shows a side elevation view, partially broken away
along the line II-II of FIG. 3B, of an embodiment of a tool head
according to the present invention;
[0045] FIG. 3B shows a further schematised top plan view of the
tool head of FIG. 3A;
[0046] FIG. 4A shows an elevation function for one turn for a right
side spectacle lens to be machined according to the invention;
and
[0047] FIG. 4B shows an elevation function for one turn for a left
side spectacle lens, having the same optical power as that of FIG.
4A, to be machined according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] FIG. 1 shows the prior art with a spectacle lens 1 being
provided with a prescription or free-form surface on a surface 2
thereof, for example on its rear surface. Spectacle lens 1 may be a
right side lens 1R or a left side lens 1L.
[0049] It goes without saying that the term "pairwise symmetrical,
optically effective surface", as used in the context of the present
application, all such surfaces are to be understood, i.e. not only
progressive power lenses already mentioned as an example. Instead,
the invention may be used in all cases of optically effective
surfaces used in pairs, for example lenses and mirrors for
binocular applications as in telescopes, microscopes, etc. Just for
the sake of descriptiveness the invention will hereinafter be
explained with regard to the example of progressive power spectacle
lenses, briefly referred to as "spectacle lenses".
[0050] Initially, spectacle lens 1 is held as an unmachined blank
in a mounting apparatus 3 being a part of a work piece spindle.
Mounting apparatus 3 is adapted to rotate about a first axis 4 by
predetermined angles .phi. or angular steps. Mounting apparatus 3,
further, is adapted to be displaced by predetermined distances Z or
linear steps along first axis 4.
[0051] A rotatable tool head 5 has a milling tool 6 in the area of
its free end. Milling tool 6 is in engagement with surface 2 at a
predetermined point. In practice there are several such milling
tools distributed around the periphery. The milling tools,
preferably, consist of a cutting edge only. Tool head 5 is adapted
to be rotated about a second axis 7 at a high rotational speed of,
for example, about 10,000 rpm, as indicated by an arrow C. Second
axis 7, as known per se, is inclined relative to first axis 4 by an
angle .alpha. of, for example, about 105.degree.. Further, it is
adapted to be displaced by predetermined distances X or linear
steps along a third axis 8 extending perpendicular to first axis 4
and may also extend perpendicular to the drawing plane of FIG.
1.
[0052] By means of displacement movements Z, .phi., and X a first
point of engagement of milling tool 6 at the rim of surface 2 may
be set in a first operating step. Spectacle lens 1 is then rotated
(.phi.) in a predetermined direction of rotation by rotation about
first axis 4, and tool head 5 is simultaneously fed in (X) along
third axis 8. This results in a spiralled path of the point of
engagement of the cutting edge of milling tool 6 with surface 2,
wherein the spiralled path is set narrowly. By that milling the
lens is machined down to a small overmeasure.
[0053] In a second operating step a lathing tool (not shown in FIG.
1) is brought into contact with surface 2 at a second point of
engagement for the fine machining of surface 2. The lathing tool is
likewise arranged on tool head 5, and is somewhat set back with
regard to the cutting circle of milling tool 6. For that purpose,
the lathing tool is rotated about a certain angular step until a
cutting edge of the lathing tool is positioned at the predetermined
second point of engagement, and then rotates no more.
[0054] By way of the same sequence of movements the cutting edge of
the lathing tool is now also guided along a spiralled path over
surface 2. While the cutting edge of the lathing tool moves along
the spiralled path, spectacle lens 1 is, additionally, fed in
continuously along first axis 4 (Z), such that an elevation
function is generated corresponding to the desired shape of surface
2, for example a free-form surface.
[0055] FIG. 2A shows a first elevation function 10 of the formula
Z.sub.R=f(.phi..sub.R) for one turn and for a right side spectacle
lens 1R. As one can see, elevation function 10, with the selected
direction of rotation of spectacle lens 1R, is run through in a
first machining direction, as symbolized by an arrow 12.
[0056] FIG. 2B shows a machining process Z.sub.L=f(.phi..sub.L) for
a left side spectacle lens 1L of same optical power as in FIG. 2A.
The elevation function 14 is essentially mirror symmetrical as
compared to elevation function 10 from the right side spectacle
lens. The corresponding second machining direction 16 is unaltered
when the direction of rotation is likewise unaltered. As a result,
in conventional machining of right side spectacle lenses 1R and
left side spectacle lenses 1L of same optical power, the sections
of the elevation functions 10 and 14 of different gradient are run
through in opposite directions. This results in different form
defects which, therefore, have to be compensated for by means of
different shaping lead values. A positive gradient in a certain
point of first elevation function 10, namely, effects an
acceleration of the corresponding displacement unit, whereas the
corresponding point on the second elevation function 14 has a
negative gradient, i.e. a gradient of same absolute value but of
opposite sign, which results in a deceleration of the same
displacement unit. As a consequence, different form defects are
generated.
[0057] FIGS. 3A and 3B show an embodiment of a tool head 30
according to the present invention.
[0058] Tool head 30 has an axis 31 of rotation and is provided with
a chucking taper 32 having an axial stop 34. The free end of tool
head 30 is configured by a tool carrier section 36, the terminal
plane 37 of which carrying tools, as can best be seen in FIG. 3B.
The tools, for the sake of simplicity, are shown merely as
geometrical symbols which do not correspond to their actual shape.
This holds likewise true for the distribution of the tools about
the periphery of terminal plane 37.
[0059] On the left side of FIG. 3A on can see a circular disk
shaped milling tool 38 having a milling cutting edge 39. Milling
tool 38, preferably, consists of milling cutting edge 39 only.
Milling cutting edge 39 has a point 40 of engagement which is
located radially outwardly and at which the chip removing from
surface 2 takes place. When tool head 30 rotates about axis 31
during milling, point 40 of engagement moves along a cutting circle
41 having a radius r.sub.F. As shown in FIG. 3B, milling tool 38 is
just one of altogether eight such tools being distributed about the
periphery of terminal plane 37.
[0060] Point 40 of engagement is located within a plane 42, namely
a radial plane with respect to axis 31 of rotation. Plane 42 has a
predetermined axial distance, for example with regard to stop 34,
as indicated by an arrow 44.
[0061] On the right side of FIG. 3A one can see a lathing tool 48R
being one of two lathing tools 48A, 48B of a pair, as shown in FIG.
3B. Moreover, there is provided still another pair of lathing tools
70R, 70L.
[0062] According to FIG. 3A, lathing tool 48A comprises a lathing
cutter carrier 50. Lathing cutter carrier 50 is affixed to a recess
58 of tool carrier section 36 by means of a first clamping bolt 52
and a second clamping bolt 54 being, preferably, axially flush with
the latter.
[0063] Lathing cutter carrier 50, prior to be affixed, is adapted
to be adjusted in its position relative to tool carrier section 36
by means of adjustment bolts 56 and 57. Adjustment bolt 56 extends
parallel to axis 31, such that lathing cutter carrier 50 is adapted
to be thereby affixed axially. By doing so, a lathing cutting edge
60 at the free end of lathing cutter carrier 50 may be adjusted
such that its point 62 of engagement comes to lie exactly within a
predetermined plane, for example within plane 42, as indicated by
an arrow 64.
[0064] In addition, a radial adjustment option for lathing cutter
carrier 50 may be provided by means of the second adjustment bolt
57. Further adjustment bolt 57 makes sense when the radial
positioning of point 62 of engagement is not already set by the
manufacturer's grinding of lathing cutting edge 60.
[0065] In any event, point 62 of engagement of lathing cutting edge
60 lies within cutting circle 41 of milling tool 38 at a distance d
thereto, as clearly shown in FIG. 3B. Then lathing tools 48, 70 are
out of engagement when milling tools 38 are in engagement. For
bringing one of lathing tools 48 or 70 into engagement for
subsequent lathing, tool carrier 30 is rotated just by a certain
angle corresponding to the desired point of engagement. In that
position tool head 30 is guided along the elevation function of the
spectacle lens.
[0066] Insofar it is preferred, as already mentioned, to provide on
the periphery of the cutting edge carrier section two lathing tools
48R and 48L two times as a pair, i.e. pairwise, wherein the cutting
edges of the pair 48R/48L are oppositely directed in the peripheral
direction.
[0067] Right side spectacle lens 1R is machined by means of tool
head 30 in the same manner as described above with regard to FIG.
1. When doing so, a first direction of rotation .phi. is set for
the rotation of spectacle lens 1R, for example a clockwise
direction in a top plan view on surface 2. Insofar, lathing tool
48R is used.
[0068] For the machining of left side spectacle lens 1L one
proceeds in the same manner, however, while setting an opposite
direction of rotation -.phi. during lathing, being a
counter-clockwise direction in the above given example. Insofar,
the oppositely directed cutting edge of lathing tool 48L of pair
48R/48L is used.
[0069] Second pair 70R/70L may be of another design as compared to
pair 48R/48L, for machining lenses from another material, for
example. However, it may also be of same design in order to be
exchanged in the event that pair 48R/48L becomes worn out or
damaged.
[0070] FIGS. 4A and 4B illustrate the operation with the help of
elevation functions of one turn for a right side and a left side
spectacle lens.
[0071] One can see that first function 20, i.e.
Z.sub.R=f(.phi..sub.R) for the right side spectacle lens is run
through in an unaltered machining direction 22, whereas second
function 24, i.e. Z.sub.L=f(.phi..sub.l) for the left side
spectacle lens is run through in the opposite machining direction
26. Thereby, the sections of the functions 20, 24 having different
gradients are run through in the same direction during machining.
Corresponding points of elevation functions 20, 24, therefore, have
same gradients of same sign in that case, such that the
corresponding displacement unit is accelerated in the same manner
during the machining.
* * * * *