U.S. patent application number 13/771723 was filed with the patent office on 2016-02-25 for preformed block piece having a holding surface with an axis that is offset relative to the axis of rotation of the block piece.
This patent application is currently assigned to Schneider GmbH & Co. KG. The applicant listed for this patent is Schneider GmbH & Co. KG. Invention is credited to Ulf BOERNER, Helwig BUCHENAUER, Klaus KRAEMER, Gunter SCHNEIDER.
Application Number | 20160052097 13/771723 |
Document ID | / |
Family ID | 37188909 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160052097 |
Kind Code |
A9 |
SCHNEIDER; Gunter ; et
al. |
February 25, 2016 |
PREFORMED BLOCK PIECE HAVING A HOLDING SURFACE WITH AN AXIS THAT IS
OFFSET RELATIVE TO THE AXIS OF ROTATION OF THE BLOCK PIECE
Abstract
A block piece for holding an optical lens to be machined, with a
coupling part for being held in a workpiece chuck and with a
holding part for fastening the lens. The holding part has a convex
or concave holding surface corresponding to a first side of the
lens. The holding surface is, according to the shape of the lens to
be held, provided in the form of a negative free-forming surface,
and the block piece is made from a plastic that can be machined.
The principal axis of the holding surface is arranged set off
and/or tilted relative to the axis of rotation of the coupling
part
Inventors: |
SCHNEIDER; Gunter; (Marburg,
DE) ; BUCHENAUER; Helwig; (Dutphetal-Buschenau,
DE) ; BOERNER; Ulf; (Marburg, DE) ; KRAEMER;
Klaus; (Dautphetal-Friedensdorf, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schneider GmbH & Co. KG |
Fronhausen |
|
DE |
|
|
Assignee: |
Schneider GmbH & Co. KG
Fronhausen
DE
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20130228961 A1 |
September 5, 2013 |
|
|
Family ID: |
37188909 |
Appl. No.: |
13/771723 |
Filed: |
February 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11795729 |
Jul 20, 2007 |
|
|
|
PCT/EP06/64689 |
Jul 26, 2006 |
|
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13771723 |
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Current U.S.
Class: |
269/329 |
Current CPC
Class: |
B24B 13/0057 20130101;
Y10T 156/1064 20150115; B24B 9/146 20130101; B23Q 3/105 20130101;
B32B 38/10 20130101 |
International
Class: |
B23Q 3/10 20060101
B23Q003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2005 |
DE |
10 2005 038 063.8 |
Claims
1. A block piece for holding an optical lens being machined,
comprising: a coupling part, having an axis of rotation, for
holding in a workpiece chuck, and a holding part adapted for
holding the lens, wherein the holding part has a convex or concave
holding surface adapted to be adhered to a first side of the lens,
wherein the holding surface, according to a shape of the first side
of the lens prior to the lens being connected, is configured as a
spherical, aspherical, toroidal, progressive or asymmetrical
negative surface in order to ensure support of the lens being
machined and the block piece is made of a machinable plastic,
whereby the entire holding surface has a required inflexible
configuration that provides an axially fixed block piece to ensure
a defined axial bearing of the lens against the holding surface,
and wherein the holding surface has a negative form with reference
to the first side of the lens being connected via adhesive thereto;
and wherein a principal axis of the holding surface is arranged set
off tilted relative to the axis of rotation of the coupling
part.
2. The block piece according to claim 1, wherein at least one
channel for a pressurizing agent is provided between the holding
surface and an outer surface, by which the pressurizing agent from
an outside can be brought into a region between the holding surface
and the lens being held.
3. The block piece according to claim 2, wherein at least one
equalizing channel is provided in the holding surface to receive
excess adhesive.
4. The block piece according to claim 3, wherein the equalizing
channel is configured in star shape, spiral shape, or circle at an
outer margin of the holding surface or a combination thereof.
5. The block piece according to claim 2, wherein the pressurizing
agent channel has a cross section widening in the direction of flow
of the pressurizing agent.
6. The block piece according to claim 2, wherein several
pressurizing agent channels are uniformly distributed and issue
onto the holding surface.
7. The block piece according to claim 2, wherein the pressurizing
agent channel has a funnel-like mouth region.
8. The block piece according to claim 2, wherein the pressurizing
agent channel emerges in at least one of a region of a center axis
of the holding surface and in a region of a point-like support
locations.
9. The block piece according to claim 1, wherein the block piece is
configured as an injection molded plastic part.
10. The block piece according to claim 1, wherein the block piece
is configured at least in two parts.
11. The block piece according to claim 1, wherein the holding
surface has several point-like support locations for the lens being
held, and the remaining part of the holding surface is somewhat set
back relative to the support locations.
12. The block piece according to claim 11, wherein the holding
surface or at least the point-like support locations of the holding
surface can be activated in order to generate an adhesive force and
possess adhesive properties.
13. The block piece according to claim 11, wherein a double-sided
adhesive film to secure the lens is applied to the holding surface
at least in the region of the point-like support locations.
14. The block piece according to claim 11, wherein the holding
surface has three point-like support locations.
15. The block piece according to claim 11, wherein the remaining
set-back part of the holding surface has approximately the shape of
the first side of the lens being held.
16. The block piece according to claim 11, wherein the point-like
support locations of the holding surface form part of an imaginary
surface, and the imaginary surface describes the shape of the first
side of the lens being held.
17. The block piece according to claim 11, wherein the set back of
the remaining part of the holding surface relative to the support
locations is between 0.01 mm and 0.5 mm.
18. The block piece according to claim 1, the holding surface has
been shaped to produce the offset tilt of the principal axis of the
holding surface relative to the axis of rotation of the coupling
part.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of co-pending
U.S. patent application Ser. No. 11/795,729.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a block piece for the holding of an
optical lens being machined with a coupling part, having an axis of
rotation, for the holding and orienting in a workpiece chuck, and a
holding part for the securing of the lens, wherein the holding part
has a convex or concave holding surface corresponding to a first
side of the lens. A holding surface is thus considered to be convex
or concave if it is raised relative to the ground, i.e., bulging
outward, or sunken, arching inward, regardless of whether it is
configured as spherical or aspherical.
[0004] 2. Description of Related Art
[0005] A method for cutting of a contact lens out of a cylindrical
blank is already familiar from European Patent EP 1 112 143 B1 and
corresponding U.S Pat. Nos. 6,786,802 and 6,315,650. Here, in order
to machine one base side of the blank it is fastened to a first
block piece of machinable plastic material and then the machined
base side is placed on a second block piece in order to fabricate
the front side. The front side of the blank can be aspherical or
toroidal in configuration, while the base side toward the blank is
spherical in configuration.
[0006] When manufacturing aspherical spectacles glasses made from
plastic, it is generally customary to bind them to the block piece
by a low-melting alloy. For this, a space bounded by the block
piece and the lens is filled with the alloy, so that the alloy
takes on the form of the aspherical surface of the lens and binds
the lens to the block piece. Using the alloy is cost-intensive and
detrimental in terms of the time course of the process, since a
relatively large amount of alloy is needed. The alloy has to be
hot-molded, cooled down, and remelted for purposes of removal from
the block. During the cool-down process, the relative position
between the block piece and the lens has to be fixed. The side of
the lens being bonded in this case is spherical, in order to
guarantee tightness when placed against the block piece for filling
with liquid alloy. For aspherical surfaces, a sealing lip is
provided between the block piece and the lens, ensuring a tight
abutment.
[0007] Alternatively, Japanese Patent Application JP 11198014 A
describes how to hold the lens by means of a deformable wax or how
to mold this against the lens and thereby fix the lens.
SUMMARY OF THE INVENTION
[0008] The basic problem of the invention is to configure a block
piece and a method for putting on and removing from the block so
that an optimal putting on and taking off of the lens is
assured.
[0009] The problem is solved according to the invention in that the
holding surface, according to the shape of the lens being held or
its side being held, is configured as an aspherical, i.e.,
toroidal, progressive or asymmetrical negative surface or as a
negative free-forming surface, and the block piece is made of a
machinable plastic. This ensures that the first side of the lens
can be brought to bear against the holding surface with almost no
spacing and thus the amount of adhesive to be used is reduced to a
minimum. The nature of the bearing relationship between the holding
surface and the first side or lens surface depends on the roughness
of the surfaces, the viscosity of the adhesive used, and the
bearing or pressing force employed.
[0010] Ideally, as little adhesive as possible is present between
the two surfaces. The adhesive here does not constitute a spacing
agent, but rather serves merely to fill up or seal off the gap or
roughness present between the two surfaces. Since it is necessary,
as a rule, to apply heat in conjunction with the activation of the
adhesive or the application of the adhesive, a correspondingly
reduced amount of heat is needed in the case of the invention for
the activation or application of the extremely thin glue layer thus
formed.
[0011] Furthermore, besides the aspherically configured first side
of the lens, the second side of the lens for the machining can now
also be aspherically, i.e., toroidally or progressively configured,
so that the shapes or features which establish the optical
properties of the lens, such as radii, optical axes, partial
optical surfaces or prisms of the lens, can be optimally
distributed over the two sides of the lens.
[0012] Moreover, the entire surface of the lens can rest against
the holding surface and thus have its entire surface supported by
it, and due to the machinability of the block piece any
configuration of the lens is possible in terms of its diameter or
width.
[0013] For purpose of holding of special spherical lenses, the
holding part has a convex or concave spherical holding surface with
a principal axis that describes the orientation of the partial
spherical surface so formed.
[0014] According to the invention, the holding surface is
configured as a negative surface to the lens, corresponding to the
orientation of the lens being held, and the principal axis of the
negative surface or holding surface is arranged set off from and/or
tilted to the axis of rotation of the coupling part. Thus, the
spherical surface of the block piece is configured individually to
the orientation of the lens being held, so that the subsequent
machining process can be optimally designed.
[0015] It is advantageous that the holding surface can also be
configured as spherical, in addition to the above mentioned surface
forms, and have several, especially three, point-like support
locations for the lens being held, depending on the surface form or
its orientation, and the rest of the holding surface is somewhat
set back relative to the support locations. This ensures a defined
bearing of the lens against the holding surface. In this variant
embodiment, although somewhat more adhesive is required than when
the entire surface of the lens is abutting, one can at least
determine the support locations even for lenses whose first side
being held is not known, while the rest of the lens surface need
only be determined roughly or partially with slight precision.
[0016] It is of advantage that the remaining set-back part of the
holding surface has approximately the shape of the first side of
the lens being held. With regard to the previously mentioned
determination of the lens surface, it is possible to reduce the
accompanying process of determining or surveying the first side to
a necessary degree, so that one can also use measuring means with
low resolution, such as sensors or spiked gages. The spiked gauge
is used for simultaneous detection of several measurement points on
the surface.
[0017] Moreover, the machining chip-removal step can be reduced to
a sufficient degree of complexity, so that a faster overall
production of the bearing surface is assured.
[0018] For this, it is advantageous that the point-like support
locations of the holding surface form part of an imaginary surface,
and the imaginary surface describes the form of the first side of
the lens being held. Thus, besides the defined abutment or bearing
of the lens, the support locations themselves are defined. The lens
can be oriented and supported or fixed exactly by the bearing
surface. The free space existing between the bearing surface and
the lens is limited here to a relatively small and estimable
degree, so that very little adhesive is needed according to the
invention. The bearing surface stands back around 0.01 mm to 0.5 mm
relative to the support locations. Especially for lenses with
unknown surface form of the first side being held, which have to be
surveyed with the above-mentioned measuring means, the aforesaid
standback distance is generally larger than for lenses whose
geometry of held surface is known. In exceptional cases, said
distance might even be greater than 0.5 mm. For the holding of
unknown lenses, the setback holding surface has to be simplified,
since the surface being held can only be determined with a limited
resolution. This is not the case for lenses with known surface
form. Here, the approximation of the holding surface serves only to
speed up the fabrication of same, since the accompanying
calculation expense of the machining equipment is reduced. But the
support locations in this case are part of the imaginary surface,
which corresponds exactly to the surface form of the first side
being held.
[0019] Most lenses have at least partial spherical regions, despite
their overall form being aspherical. The support locations will be
situated preferably in such partial spherical regions, which are
then mapped exactly on the holding surface as part of the overall
imaginary surface.
[0020] An additional possibility, according to one embodiment, is
that at least one channel for a pressurizing agent is provided
between the holding surface and an outer surface, by which
pressurizing agent from the outside can be brought into the region
between the holding surface and the lens being held. For the
deblocking or releasing of the lens from the block piece, it is
advantageous to bring in pressurizing agents such as air, water, or
fluids with other viscosities between the holding surface and the
particular lens, since this deblocking step can be done very
swiftly and without bringing in additional heat. The pressurizing
agent channel arises at an outer surface of the block piece, so
that an appropriate connection for pressurizing agent or an
appropriate pressurizing agent line can be hooked up.
[0021] Also of advantage for this is that at least one equalizing
channel is provided in the holding surface to receive excess
adhesive. The equalizing channel can be fashioned as a groove,
borehole or recess, so that when a lens is put in place the excess
glue located between the lens and the holding surface is pressed
into the available equalizing channel or channels. In this way, the
portion of adhesive located between the lens and the holding
surface can be reduced to the aforesaid minimum.
[0022] Moreover, it is advantageous that the equalizing channel
and/or the pressurizing agent channel is configured in star,
spiral, and/or circle shape. The number and size of the respective
channels should be chosen so that the lens is also supported by its
entire surface and adequately by the block piece so that the block
piece does not lose the required rigidity. The equalizing channel
can be provided as a circle at the outer margin of the holding
surface, so that the excess adhesive emerging at the side when the
lens is placed on the block is captured and does not run onto the
workpiece chuck.
[0023] It is also advantageous that the pressurizing agent channel
has a cross section widening in the direction of flow of the
pressurizing agent. When the lens is placed on the block piece, the
adhesive applied is necessarily forced into the existing
pressurizing agent channels, so that it has to be forced out once
again when the lens is loosened. Thanks to the aforesaid
configuration of the cross section, it is easily possible to force
out the at least partly hardened adhesive, since there is no
undercut present.
[0024] Advantageously, several pressurizing agent channels are
uniformly distributed and issue onto the holding surface, and the
pressurizing agent channel has a funnel-like mouth region. The
various pressurizing agent channels can be provided in place of the
aforesaid equalizing channels, since these will necessarily take up
excess adhesive. The distribution of the pressurizing agent
channels ensures an optimal loosening and an optimal deblocking of
the lens, so that it is not damaged during the release process.
[0025] In conjunction with the configuration and arrangement of the
invention it is of benefit that the pressurizing agent channel
emerges centrally, in the region of a center axis of the holding
surface and/or in the region of the point-like support locations.
The block piece is used to make the most diverse of lens forms, and
very small lenses also have to be taken into consideration. With
the arrangement of the pressurizing agent channel near the center
of the holding surface, it is available in any case, regardless of
the size of the lens being made and the cutting work involved in
making the lens, on the one hand, and the size of the block piece,
on the other. When the pressurized agent channel or its mouth is
arranged in the region of the support locations, the deblocking
process is relatively simple, since the separating of the lens from
the respective relatively small support location occurs with no
additional expense.
[0026] Moreover, it is advantageous for the block piece to be
configured as an injection molded plastic part. This ensures a
favorable and very fast production of the block piece.
[0027] Furthermore, it is advantageous that the holding surface or
at least the point-like support locations of the holding surface
can be activated in order to generate an adhesive force and possess
adhesive properties. The block piece or at least the holding part
can be formed from two kinds of plastic during the fabrication
process, regardless of whether the block piece is a single or
multiple part, to meet the respective requirements, i.e., those of
a coupling part, on the one hand, and those of a holding part with
holding surface or a support location, on the other hand. The
holding part could be made, at least in the region of the holding
surface or the support locations, from a plastic which develops
adhesive properties after an activation by heating or melting or
etching, so that the lens can be glued onto the holding surface or
connected to it without applying additional adhesive or without the
use of an adhesive film. In the case of heating, very slight
thermal input is needed, and thus a rapid cool-down is assured.
[0028] It is advantageous that the block piece is configured at
least in two parts. Thus, after fabrication of the lens, it is only
necessary to dispose of the machined holding part, while the
coupling part can be reused.
[0029] Moreover, it is advantageous that a double-sided adhesive
film to secure the lens can be applied to the holding surface or at
least in the region of its point-like support locations. Since the
lens has to be protected against damage in any case by placing a
film on the side being held, the use of a double-sided adhesive
film which is glued first to the first side of the lens and
secondly serves to attach it to the holding surface represents an
optimal solution.
[0030] The problem is also solved by the method for placing an
optical lens, with a first side and a second side being machined,
on a block piece made of plastic, with a coupling part for a
workpiece chuck and a holding part with a holding surface for the
lens. Before being placed on the block, the holding surface is
machined, thus generating a negative form corresponding to the
first side of the lens, which has the same radii, partial surfaces,
and optical axes, or an approximation thereto. An adhesive is
placed on the holding surface and/or the lens and/or the holding
surface is activated in order to develop an adhesive force.
[0031] The holding surface of the block piece and the first side of
the lens are oriented to each other in terms of their respective
position or orientation of the optical axes relative to each other,
the first side and the holding surface are joined or at least
brought to partly bear or rest against each other, and thus a pair
of block piece and lens is formed. Preferably, the mean spacing
between the holding surface and the lens is between 0.01 mm and 0.5
mm. Theoretically, the lens is supported in this case by at least
three points and is statically determined on the holding surface,
while for an adhesive with high viscosity and slight supporting
forces there does not need to be a direct bearing of the lens.
Thanks to this, the first side of the lens can be brought to bear
against the holding surface with almost no spacing and thus the
quantity of adhesive to be used is reduced to a minimum. Since it
is generally necessary to apply heat in conjunction with the
activation of glues or the applying of glues, a correspondingly
reduced heat input is needed for the activation or application of
the extremely thin glue layer which is formed according to the
invention.
[0032] It is of advantage that the holding surface be machined in
such a way as to generate several point-like support locations for
the lens being held, in particular, three, and a portion of the
holding surface standing somewhat back from the support locations,
and the point-like support locations of the holding surface form
part of an imaginary surface which describes the form of the first
side of the lens being held and the setback part describes only
approximately the form of the lens being held.
[0033] Finally, it is of advantage that the process steps of
shaping and applying of adhesive and/or the process steps of
applying adhesive and orienting be executed or worked off in
reverse sequence. To the extent that the adhesive is applied to the
lens, the process step of applying of adhesive can also occur prior
to the step of shaping, so that only after the adhesive is applied
to the lens does the machining of the block piece occur.
Furthermore, it is also possible to apply the adhesive only after
the orienting of the block piece and fens, especially when there
needs to be as little time as possible elapsing between the
applying of the adhesive and the moment of placing the lens on the
holding surface, owing to the setting time of the adhesive.
[0034] For this, it is also advantageous that the adhesive is
applied to the support locations in the form of a spiral, star,
and/or point. When the adhesive is applied in a spiral, the
centrally provided pressurizing agent channel and the other
pressurizing agent channels should be kept clear so that the
pressurizing agent for purposes of deblocking can expand into the
open space formed by the lens and the holding surface, on the one
hand, and adjoining beads of adhesive, on the other. The
propagating dynamic pressure built up by the flowing pressurizing
agent thus provides an ample detaching force, ensuring the
deblocking of the lens or the loosening of the lens afterwards.
[0035] Finally, it is of advantage that the adhesive is hardened by
using thermal radiation and/or UV radiation. Depending on the
adhesive used, this hardening is possible by UV radiation or some
other energy input, such as heating or the like.
[0036] Moreover, it is advantageous that the adhesive is configured
as a double-sided adhesive film and it is brought to bear against
the holding surface and the lens.
[0037] Since the lens has to be protected against damage in any
case by placing a film on the side being held, the use of a
double-sided adhesive film which is glued first to the first side
of the lens and secondly serves to attach it to the holding surface
represents an optimal solution.
[0038] Furthermore, it is advantageous that at least one equalizing
channel is worked into the holding surface before or after the
machining of the holding surface, to receive excess adhesive,
and/or at least one recess fashioned as a pressurizing agent
channel is worked into the block piece before or after the
machining of the holding surface, ensuring communication between
the holding surface and the surroundings. Depending on the desired
lens form, an individual configuring of the equalizing and
pressurizing agent channels may be required and advantageous to the
invention. The connection of different channels is also possible,
emerging at different points on the holding surface.
[0039] Finally, it is of advantage that the hardening of the
adhesive in terms of duration and/or intensity occurs in such a way
that the adhesive is basically only hardened completely in the
region between the lens and the holding surface and it is not
hardened in the region of the equalizing channel and/or the
pressurizing agent channel. Thus, when deblocking or releasing the
lens, the inflowing pressurizing agent is not prevented from
entering between the lens and the holding surface, so that a
simpler and more controlled detaching of the lens is assured in
view of the nonexistent glue forces inside the channels.
[0040] It is also advantageous for this that the machining and/or
polishing of the second side of the lens occur after connecting the
lens to the block piece. The lens placed on the block according to
the invention can now be machined in any manner, and the particular
pair of block piece and lens remains as a unit for all further
processing steps after the fabrication, until the lens is finally
ready.
[0041] Moreover, it is advantageous that the pair of block piece
and lens is clamped in an additional workpiece chuck for the
polishing of the lens. The block piece of the invention or the pair
formed by the block piece and lens according to the invention can
be used in all workpiece chucks or block piece holders required for
the processing at stations further downstream.
[0042] Moreover, it is advantageous that the coating of the lens on
the block occurs after the machining and/or polishing of the lens
and that at least one pair of block piece and lens is placed in an
additional block piece holder for the coating of the lens. As a
rule, several lenses will be coated at the same time, and these or
the pairs of block piece and lens will be arranged one next to the
other in the area of a vapor deposition or coating source. It is
very important that only the first side being machined and the
marginal zone of the lens be coated. Since, according to the
invention, the second side not being machined is covered for its
entire surface by the block piece, it remains inevitably free of
unwanted coating agent. The block piece of the invention remains
with the lens, as part of the pair of block piece and lens, and it
can be received by the block piece holder for purposes of
coating.
[0043] Finally, it is advantageous to machine or polish the
marginal zone R of the pair of block piece and lens after the
coating of the lens. It is desirable, after the coating of the
lens, to finish the marginal zone of the now coated lens, where
coating errors may occur due to contour working and surface
stresses. According to the invention, this processing step of
adjusting the lens size and the machining of the marginal zone for
mounting in a spectacles frame comes after the coating. Thanks to
the machinable and grindable block piece, which remains on the lens
according to the invention, this can be accomplished with no
further reblocking expense, regardless of its size and the shape of
the marginal zone. The block piece of the invention also ensures a
free machining of the lens without hindrance from otherwise present
clamping or chucking devices. Even borings and the like can be
easily done.
[0044] Moreover, it is advantageous that pressurizing agent for
deblocking the lens is introduced via the pressurized agent channel
between the first side of the lens and the holding surface of the
block piece or at least the point-like support locations of the
holding surface. Depending on the configuration of the bonding
agent in terms of the form when applying the bonding agent or
adhesive, the pressurizing agent propagates into the above
described, not sealed free space or gap between lens, holding
surface, and beads of adhesive, so that the detaching of the lens
is gradually achieved. But, even when adhesive is applied over the
entire surface, i.e., when there are no unsealed places between the
holding surface and the lens, as in the case of adhesive film or
other glue variants, such as melting on the holding surface, the
steady propagation of the pressurizing agent from the mouth of the
pressurizing agent channel or the various mouths is assured.
[0045] Furthermore, it is advantageous that the adhesive and/or the
lens is heated or cooled for the deblocking and/or loosening of the
lens. Since thanks to the invention it is possible to use very
little adhesive or bonding agent, the process of detachment by
heating or cooling the adhesive is very fast, as only a little
adhesive is present. In the case of cooling, the adhesive becomes
brittle.
[0046] It is advantageous according to the invention that, for the
deblocking and/or loosening of the lens, the remaining holding part
and/or the coupling part of the block piece is deformed so that the
holding surface is deformed and at least partly loosened from the
lens. For this, the remaining holding part and/or the coupling part
is taken up in a collet chuck acting in the radial direction,
generating an appropriate clamping force, so that the remaining
holding part and/or the coupling part is upset. As a result of this
upsetting, the remaining holding part arches up and the lens is
detached from the holding surface or bonding agent. The fact that
the glue layer is very thin, according to the invention, also
favors the deblocking operation.
[0047] Alternatively, it is beneficial that the holding part and/or
the coupling part of the block piece is provided with at least one
slot or slotted prior to the deforming, and only then deformed. For
this, the pair of block piece and lens must be removed from the
workpiece chuck and possibly be held at the lens side, so that the
coupling part can be slotted by means of a saw or a milling
cutter.
[0048] It is of advantage here that the holding part and/or the
coupling part be subjected to a clamping force in a direction
transverse to the slot for purposes of deformation. The slot will
be deep enough so that the slot at least partly closes during the
subsequent deformation process by clamping or compressing at least
the coupling part, and the holding part also becomes deformed, so
that it is loosened from at least part of the lens. Preferably, the
slot will extend until just before the glass, i.e., just into the
holding part, so that a remaining wall thickness of around 1 mm to
2 mm remains for the block piece. During the clamping, the
loosening process is initiated at the margin and then continues
toward the middle, thanks to the lasting deformation.
[0049] Other benefits and details of the invention are explained
below with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIGS. 1 to 12 show a perspective representation of the block
piece and the lens during the various machining processes,
[0051] FIG. 13 shows a holding part with a regular spherical axis,
and a tilted spherical axis represented, and
[0052] FIG. 14 is a view like that of FIG. 13, but showing a
holding part with a holding surface that provides three point
support for a lens.
DETAILED DESCRIPTION OF THE INVENTION
[0053] A block piece 1 shown in FIG. 1 has a coupling part 1.1 for
holding and orienting in a workpiece chuck 3 or block piece chuck
per FIG. 2, as well as a holding part 1.3 with a holding surface
1.4 for a lens 2 configured as a spectacles glass per FIG. 4. The
holding part 1.3 has so large a diameter that every spectacles
glass being fabricated can be brought to bear against the holding
surface 1.4 with the entire surface of a second side 2.2. At the
center of the holding surface 1.4, the block piece 1 has the mouth
of a pressurizing agent channel 1.6, by which pressurizing agent
can be taken from an outer surface 1.7 into the region of the
holding surface 1.4. The workpiece chuck 3 per FIG. 2 has several
recesses 3.1 for detent screws, distributed about the
circumference, in order to attach the flange of a tool spindle, not
shown.
[0054] The coupling part 1.1 has, besides a conical or cylindrical
support surface of a particular diameter, also a bearing surface at
its end, working in the axial direction, and it has two grooves
which can be mounted by form-fitting in the workpiece chuck 3, one
a driving groove 1.9 for the rotary propulsion of the block piece 1
and one an orienting groove 1.8, serving to line up the block piece
1 relative to the workpiece chuck 3.
[0055] According to FIG. 2, the block piece 1 or the holding
surface 1.4 of the block piece 1 is machined by means of a milling
head 7 with several blades 7.1. The holding surface 1.4 in this
process is given the negative form corresponding to the second side
2.2 of the spectacles glass 2 being fastened. FIG. 2 shows,
moreover, a connection opening 1.6' of the pressurized agent
channel 1.6, which is situated on the outside of the block piece
1.
[0056] The holding surface 1.4 shown in FIG. 3 now represents the
negative form to a first side 2.1 of the spectacles glass 2 per
FIG. 4. Adhesive or bonding agent 5 in the form of a bead is
applied in spiral manner to the holding surface 1.4 by a spray
nozzle or adhesive nozzle 8. Thus, the mouth of the centrally
placed pressurized agent channel 1.6 remains free of adhesive. The
holding surface 1.4 thus prepared likewise has an imaginary optical
axis, as negative surface, just like the first side 2.1 of the lens
2 being supported per FIG. 4.
[0057] According to FIG. 4, the spectacles glass 2 is placed or
glued by its first side 2.1 against the holding surface 1.4 of the
holding part 1.3. The rough blank of the spectacles glass 2 shown
here is larger in terms of diameter than the holding part 1.3. But
this is not detrimental, since the spectacles glass 2 being
fabricated is clearly smaller than the rough blank, so that it
ultimately lies, as described above, with its entire surface on the
holding part 1.3. The blank or the lens 2, together with the block
piece 1, form a so-called block piece/lens pair 1.2, which
constantly remains a single unit in the following processing
steps.
[0058] According to FIG. 5, the second side 2.2 of the lens 2 is
machined by means of the milling head 7 with several blades 7.1.
The machining is done in the direction of rotation K of the milling
head 7 and also in a feed direction V, from the outside inward.
Hence, given the superimposed rotary motions of milling head 7 and
lens 2 or workpiece spindle, a better cutting chip is produced and
there is a better supporting of the lens 2, since the cutting
forces act to the side and upward. Thus, the chip is detached
upward at the not yet fully machined surface. Such surface flaws
are worked off again in the subsequent machining. In the milling
work per FIG. 5, besides the second side 2.2 of the lens 2, a
marginal zone R of the lens and of the holding part 1.3 is also
machined.
[0059] In FIG. 6, after the milling work, it is now primarily the
second side 2.2 of the lens 2 that is machined with a turning
chisel 9 or cutting insert 9.1 of the turning chisel 9.
[0060] In FIG. 7, the second side 2.2 of the lens 2 is polished
over its entire surface by a polishing head 10 with a polishing
shoe 10.1, the entire surface being supported by the holding part
1.3.
[0061] After this, the lens 2 or the second side 2.2 per FIG. 8 is
cleaned with a cleaning brush 11, and an ultrasound cleaning is
also possible as a supplement or an alternative. In all processing
steps thus far, the block piece/lens pair has remained a single
unit. Both during the polishing and during the cleaning, the block
piece 1 or the coupling part 1.1 of the block piece 1 is taken up
in another workpiece chuck 6 with recesses 6.1 for detent screws.
The workpiece chuck 6 can also be secured in a different way.
[0062] According to FIG. 9, the first side 2.1 of the lens 2 is now
ready. It has a second optical axis 2.6, differing from an optical
axis 2.5 of the second side 2.2. Thus, the features of the lens 2
assuring the optical properties of the spectacles glass are
apportioned between the first side 2.1 and the second side 2.2 of
the lens 2, corresponding to the optical axes 2.5, 2.6.
[0063] For a coating of the second side 2.2 of the lens 2, this
along with the block piece, i.e., the respective block piece/lens
pairs 1.2, 1.2', is placed in or taken up by a bell-shaped block
piece holder 4 per FIG. 10. The block pieces 1 are normalized to
the extent that they fit into the various workpiece chucks 3, 6 and
block piece holders according to the preceding machining processes.
The first side 2.1 of the lens 2 is placed or protected with its
entire surface against the holding surface 1.4 of the holding part
1.3 so that only the second side 2.2 of the lens 2 and the marginal
zone R are coated during this coating process.
[0064] Since flaws may occur during the coating, especially in the
marginal zone of the lens 2, the marginal zone R is machined only
after the coating to produce the final shape.
[0065] According to FIG. 11, a grinding disk 12 or milling cutter
is used to grind down the marginal zone R or the circumference of
the spectacles glass 2 to the desired dimension, which dimension
will depend on a diameter .sup.P of the coupling part 1.1 of the
block piece 1. Only the marginal zone R of the spectacles glass 2
and a partial marginal zone of a holding part 1.3G is machined or
ground. The grinding disk 12, furthermore, has a peripheral groove
12.1, so that the grinding process leaves behind a corresponding
margin 2.7 on the spectacles glass 2 for fastening in a frame. The
coupling part 1.1 of the block piece 1 is taken up in another
workpiece chuck 13 with recesses 13.1 for detent screws.
[0066] According to FIG. 12, the spectacles glass 2 has been
deblocked from the holding part 1.3. For this, pressurizing agent
(not shown) was introduced via the pressurizing agent channel 1.6
between the holding surface 1.4 and the first side 2.1 of the lens
2. In view of the bead 3 of adhesive present on the holding surface
1.4, the pressurizing agent introduced propagated into the free
space formed between holding surface 1.4 and first side 2.1, on the
one hand, and the adjacent beads 5, on the other (see the direction
of flow P), thus initiating the process of detachment of the
spectacles glass 2.
[0067] As shown in FIG. 13, the holding surface 1.4 is configured
as a negative surface corresponding to the orientation of the lens
being held, and the principal axis A of the negative surface or
holding surface 1.4 is arranged set off from and/or tilted to the
axis of rotation R of the coupling part 1.1. Thus, the spherical
holding surface 1.4 of the block piece 1 is configured individually
to the orientation of the lens being held, so that the subsequent
machining process can be optimally designed. FIG. 13 shows one way
of provided the tilted offset is by tapering the thickness of the
holding part 1.3, but tilting and/or offsetting of the axis A can
also be produced by grinding out the holding part 1.3 so that
holding surface 1.4 is off center, so that the outer dimensions
(perimetric thickness) being the same as shown in the preceding
embodiments.
[0068] FIG. 14 shows an advantageous modification in which the
spherical holding surface 1.4, has several, especially three,
point-like support locations 1.5 for the lens being held. Depending
on the surface form or its orientation, the rest of the holding
surface is somewhat set back relative to the support locations.
[0069] In this embodiment, it is advantageous that the point-like
support locations 1.5 of the holding surface 1.4 form part of an
imaginary surface, and the imaginary surface describes the form of
the first side of the lens being held. Thus, besides the defined
abutment or bearing of the lens, the support locations themselves
are defined. The lens can be oriented and supported or fixed
exactly by the bearing surface. The free space existing between the
holding surface and the lens is limited here to a relatively small
and estimable degree, so that very little adhesive is needed
according to the invention. In particular, preferably, the mean
spacing between the holding surface and the lens is between 0.01 mm
and 0.5 mm. This ensures a defined bearing of the lens relative to
the holding surface. In this modified embodiment, although somewhat
more adhesive is required than when the entire surface of the lens
is abutting, one can at least determine the support locations even
for lenses whose first side being held is not known, while the rest
of the lens surface need only be determined roughly or partially
with slight precision. The point-like supports 1.5 can also serve
as a means for tilting and/or offsetting of the principal axis A
relative to the axis of rotation R.
* * * * *