U.S. patent application number 10/171178 was filed with the patent office on 2002-12-05 for lap having a layer conformable to curvatures of optical surfaces on lenses and a method for finishing optical surfaces.
Invention is credited to Dooley, Jonathan M., Goulet, Michael, Logan, David J..
Application Number | 20020182984 10/171178 |
Document ID | / |
Family ID | 23796307 |
Filed Date | 2002-12-05 |
United States Patent
Application |
20020182984 |
Kind Code |
A1 |
Dooley, Jonathan M. ; et
al. |
December 5, 2002 |
Lap having a layer conformable to curvatures of optical surfaces on
lenses and a method for finishing optical surfaces
Abstract
In a conformable lap and related method for finishing ophthalmic
lens surfaces, a rigid base surface of the lap defines a nominal
ophthalmic lens curvature corresponding to a predetermined range of
curvatures. A work surface of the lap is defined by a thin, hard,
polymeric material extending adjacent to the base surface for
contacting a selected ophthalmic lens surface and conforming to the
curvature of the selected surface. A selectively conformable
substance consisting of a mixture of thermoplastic and metallic
particles forms a layer extending between the rigid base surface
and the work surface, and is selectively changeable between solid
and non-solid forms. In its non-solid form the conformable
substance permits movement of the work surface relative to the base
surface to conform to the curvatures of any one of a plurality of
ophthalmic lens curvatures within the predetermined range of
curvatures, and in its solid form the substance fixes the work
surface in a position conforming to the curvature of a selected
lens surface and retains the conforming position during finishing
of the lens surface.
Inventors: |
Dooley, Jonathan M.;
(Bolton, CT) ; Goulet, Michael; (Hebron, CT)
; Logan, David J.; (Monterey, MA) |
Correspondence
Address: |
McCormick, Paulding & Huber
City Place II
185 Asylum Street
Hartford
CT
06103-3402
US
|
Family ID: |
23796307 |
Appl. No.: |
10/171178 |
Filed: |
June 12, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10171178 |
Jun 12, 2002 |
|
|
|
09452401 |
Dec 1, 1999 |
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Current U.S.
Class: |
451/42 ; 451/495;
451/59 |
Current CPC
Class: |
B24B 13/02 20130101;
B24B 49/14 20130101; B24B 13/005 20130101; B24B 13/012
20130101 |
Class at
Publication: |
451/42 ; 451/59;
451/495 |
International
Class: |
B24B 001/00; B24B
007/19 |
Claims
What is claimed is:
1. A conformable lap for finishing optical surfaces, comprising: a
rigid base surface defining a base curvature; a work surface
extending adjacent to the base surface for contacting a selected
optical surface and conforming to the curvature of the selected
optical surface; and a selectively conformable substance forming a
layer extending between the rigid base surface and the work surface
and selectively changeable between solid and non-solid forms,
wherein the substance in its non-solid form permits movement of the
work surface relative to the base surface to conform to the
curvature of the selected optical surface, and the substance in its
solid form fixes the work surface in a position conforming to the
curvature of the selected optical surface and retains said
conforming position during finishing of the selected optical
surface.
2. A conformable lap as defined in claim 1, wherein the selectively
conformable substance includes a thermoplastic which is in its
solid form at or below approximately the ambient temperature of the
lap and is changeable into its non-solid form in response to the
application of thermal energy thereto.
3. A conformable lap as defined in claim 2, further comprising
means for controlling the temperature of the substance for
selectively changing the substance between the solid and non-solid
forms.
4. A conformable lap as defined in claim 3, wherein the rigid base
surface is formed of a thermally-conductive material, and the means
for controlling the temperature of the substance includes means for
introducing a temperature-controlled fluid into thermal
communication with the base surface for controlling the temperature
of the base surface and, in turn, controlling the temperature of
the conformable substance in thermal communication with the base
surface.
5. A conformable lap as defined in claim 4, wherein the means for
introducing a temperature-controlled fluid includes a discharge end
having at least one opening for introducing relatively hot fluid to
an approximately central portion of the base surface and a
plurality of openings for introducing relatively cold fluid to
central and side portions of the base surface.
6. A conformable lap as defined in claim 4, wherein the means for
introducing a temperature-controlled fluid includes at least one
fluid channel coupled in fluid communication with the base surface,
and a temperature-controlled fluid source coupled in fluid
communication with the at least one conduit for introducing a
temperature-controlled fluid into thermal communication with the
base surface to thereby control the temperature of the base
surface.
7. A conformable lap as defined in claim 6, wherein the means for
introducing a temperature-controlled fluid includes a hot fluid
pipe and a cold fluid pipe.
8. A conformable lap as defined in claim 7, wherein the hot fluid
pipe and the cold fluid pipe are substantially concentric.
9. A conformable lap as defined in claim 8, further comprising a
drain pipe disposed substantially concentric with the hot and cold
fluid pipes to allow fluid to drain after being in communication
with the underside of the conformable lap.
10. A conformable lap as defined in claim 2, wherein the
selectively conformable substance further includes particles for
enhancing the thermal-conductivity of the substance.
11. A conformable lap as defined in claim 10, wherein the particles
are metal.
12. A conformable lap as defined in claim 1, wherein the work
surface is defined at least in part by a polymeric layer
superimposed over and in contact with the layer of selectively
conformable substance.
13. A conformable lap as defined in claim 12, wherein the work
surface is further defined by a finishing pad mounted on an
opposite side of the polymeric layer relative to the selectively
conformable substance.
14. A conformable lap as defined in claim 12, wherein the polymeric
layer is less than approximately 10 mils thick.
15. A conformable lap as defined in claim 1, wherein the base
curvature defines a nominal ophthalmic lens curvature, and the
layer of selectively conformable substance allows modification of
the nominal curvature within a predetermined range of ophthalmic
lens curvatures.
16. A method for finishing a selected optical surface with a
conformable lap having a rigid base surface defining a base
curvature suitable for a predetermined range of optical surface
curvatures, a work surface extending adjacent to the base surface
for contacting a selected optical surface and conforming to the
curvature of the selected optical surface, and a selectively
conformable substance forming a layer extending between the rigid
base surface and the work surface, and selectively changeable
between solid and non-solid forms, the method comprising the steps
of: determining the curvature of the selected optical surface;
selecting the base curvature and thickness of the layer of
conformable substance to allow the work surface to conform to the
curvature of the selected optical surface; changing the conformable
substance from the solid to the non-solid form; pressing the
selected optical surface into contact with the work surface, and in
turn conforming the work surface and underlying layer of
selectively conformable substance to the curvature of the selected
optical surface; with the selected optical surface pressed into
conforming contact with the work surface, changing the selectively
conformable substance from the non-solid to the solid form to
thereby cause the work surface to adopt the curvature of the
selected optical surface; and with the selected optical surface
conformably contacting the work surface, moving at least one of the
optical surface and work surface relative to the other to finish
the optical surface.
17. A method as defined in claim 16, wherein the step of moving at
least one of the optical surface and work surface relative to the
other includes moving the optical surface along a path defined by
the optical surface curvature.
18. A method as defined in claim 16, comprising the steps of:
fixedly securing the work surface, and moving the optical surface
along a predetermined path relative to the work surface.
19. A method as defined in claim 16, further comprising an
intermediate step of: placing a pad onto the work surface
subsequent to work surface adopting the curvature of the selected
optical surface; and reconforming the work surface with the pad
placed thereon to compensate for the thickness of the pad.
20. A method as defined in claim 19, further comprising a
subsequent step of directing water onto the pad.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus and method for
finishing contoured optical surfaces in accordance with particular
prescriptions, and more directly, to such apparatus and methods
incorporating work surfaces which are selectively conformable to a
broad range of optical surface curvatures for performing work
operations on these surfaces.
BACKGROUND OF THE PRESENT INVENTION
[0002] Optical surfaces of eyeglass lenses are typically prepared
in accordance with particular lens prescriptions that require the
lens have that contours which provide selected focusing or other
optical effects. The contours may be convex or concave, and a lens
may be provided with both convex and concave surfaces that act
together to produce the desired optical effect. Generally, the
surface of an eyeglass lens proximate to the eye, is ground with a
concave contour made up of compound curves. A toric surface is
found on many ophthalmic lenses, and has the contours of a section
of a toroid or donut. In general, there are two basic curvatures on
a toric surface, one corresponding to the radius of the equator and
the other corresponding to the radius of the tubular element
forming the toroid. These two curvatures are referred to
respectively as the "sphere" and the "cylinder", and together with
the "axis" angle of the cylinder, the spherical curvature of the
front surface and the index of refraction of the lens material
define the prescription power of the lens.
[0003] Conventional methods for finishing the prescription surface
of an ophthalmic lens utilize a lap having a specially contoured
surface that substantially matches the contours of the desired
prescription surface of a lens being finished. A thin finishing pad
is attached to the contoured surface of the lap, typically by
adhesive, and an abrasive material is either directed onto the pad
in the form of a slurry or is incorporated into the pad itself.
Typically, pads with an abrasive material bonded or otherwise
integrated into them are referred to as fining pads and are used
for coarser finishing operations. Fibrous pads without abrasives
are used with a slurry containing fine abrasive materials are
referred too as polishing pads. Unless otherwise specifically
stated, the term "finishing pad" is utilized throughout this
specification to refer to both types of pads, and the term
"finishing" is used throughout this specification to refer to both
types of operations.
[0004] Since the finishing pad in conventional finishing operations
is relatively thin and must take its shape from the lap, the lap in
turn must be ground with contours that essentially conform to the
prescription or curvatures of the lens being finished. As a
consequence, finishing laboratories must stock a large number of
laps corresponding to the full range of prescriptions that are
commonly required. Needless to say, a significant inventory of laps
is needed.
[0005] Alternatively, an individual lap can be ground for each
prescription as needed. U.S. Pat. No. 4,989,316 issued to Logan et
al. and assigned to the Assignee of the present invention,
describes a numerically-controlled machine for cutting a lens blank
and a corresponding lap blank to be used in finishing the lens
blank.
[0006] As a further alternative, the lens blank from which the
eyeglass lens is formed can be coarsely ground to the desired
prescription, and a conformable lap can be used as the tool for the
finishing operation. A conformable lap in general has a work
surface that is adapted to conform to the curvature of the
contoured surface ground on the lens blank. Thus, during a
finishing operation which may employ a fining or polishing pad with
slurry, the coarseness of the contoured surface is removed but the
general curvatures defined by the prescription are preserved.
Conformable laps are shown in U.S. Pat. Nos. 2,654,027; 4,831,789;
5,095,660; 5,345,725; and 5,593,340, as well as European
Application No. 0 655 297.
[0007] It is an object of the present invention to provide
conformable laps which may conform to the contours of optical
surfaces having a wide range of curvatures, and a related method
for finishing such optical surfaces.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to a conformable lap for
finishing optical surfaces, such as ophthalmic lens surfaces, and
to a related method for finishing such surfaces. The conformable
lap comprises a rigid base surface defining a nominal curvature,
such as an ophthalmic lens curvature, corresponding to a
predetermined range of curvatures. A work surface, preferably a
thin, hard, polymeric surface, extends adjacent to the base surface
for contacting a selected optical surface and conforming to the
curvature of the optical surface. A selectively conformable
substance of the lap forms a layer extending between the rigid base
surface and the work surface, and is selectively changeable between
solid and non-solid forms. In its non-solid form, the selectively
conformable substance permits movement of the work surface relative
to the base surface to conform to the curvatures of any one of a
plurality of optical surface curvatures within the predetermined
range of curvatures, and in its solid form the substance fixes the
work surface in a position conforming to the curvature of a
selected optical surface and retains the conforming position during
finishing of the selected optical surface.
[0009] In the preferred embodiment, the selectively conformable
substance is a mixture of thermoplastic and other more
thermally-conductive particles, such as aluminum, and is changeable
from its solid to its non-solid form in response to the application
of thermal energy thereto.
[0010] One feature of the present invention is that the
temperature-controlled fluid is introduced through a discharge end
of a fluid channel to change the conformable substance from solid
to non-solid form and vice-versa. The discharge end includes at
least one central opening to introduce relatively hot fluid to a
substantially central portion of the base surface and a plurality
of openings to introduce relatively cold fluid to side portions of
the base surface. The discharge end of the present invention
ensures that the conformable substance cools to accurately assume
the shape of the lens.
[0011] One advantage of the present invention is that the
conformable lap may rapidly and accurately conform to a selected
optical surface curvature to accurately finish, for example, an
ophthalmic lens surface. Another advantage of the present invention
is that a limited number of conformable laps may be provided,
wherein each lap may conform to any of a plurality of different
ophthalmic lens curvatures within a predetermined range of
curvatures.
[0012] Other advantages of the present invention will become
apparent in view of the following detailed description and
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is an exploded, partial schematic illustration of a
conformable lap and a lap mount assembly embodying the present
invention.
[0014] FIG. 2 is a schematic view of the assembled conformable lap
and lap mount of FIG. 1.
[0015] FIG. 3 is a perspective view of a discharge end of a conduit
for introducing fluid into the conformable lap of FIG. 2.
[0016] FIG. 4 is a partial schematic illustration of the assembly
of FIG. 2 showing the conformable lap fixedly secured to the lap
mount in a finishing machine.
[0017] FIG. 5 is an enlarged view of the conformable lap of FIG. 2
with a selected lens placed thereon.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] In FIG. 1, a conformable lap assembly embodying the present
invention is indicated generally by the reference numeral 10. The
lap assembly 10 includes a conformable lap 12 and a lap mount 14
for fixedly securing the conformable lap during set up and
finishing operations. The conformable lap 12 comprises a base 16
defining a rigid base surface 18, and a mounting flange 20
depending from the periphery of the base surface. A work surface 22
is superimposed over the rigid base surface 18, and a selectively
conformable substance 24 forms a layer extending between the work
surface 22 and rigid base surface 18 which is selectively
changeable between solid and non-solid forms. As is described
further below, in its non-solid form the conformable substance 24
in its non-solid form permits movement of the work surface 22
relative to the base surface 18 to conform to the curvature of a
selected optical surface, and in its solid form the substance 24
fixes the work surface 22 in a position conforming to the curvature
of the selected optical surface and retains the conforming position
during finishing of the optical surface. As also described further
below, the base surface 18 defines a base or nominal ophthalmic
lens curvature, and the layer of selectively conformable substance
24 allows the work surface 22 to conform to any of a plurality of
different ophthalmic lens curvatures within a predetermined range
of the nominal curvature.
[0019] The conformable substance 24 preferably includes a
thermoplastic selectively changeable between solid and non-solid
forms in response to the application of thermal energy thereto.
Preferably, the thermoplastic is maintained in its solid form at
the ambient temperature of the conformable lap and is changeable
into its non-solid form in response to the application of thermal
energy thereto.
[0020] In the currently preferred embodiment, the thermoplastic is
of the type sold by the Assignee of the present invention under the
trademark "Freebond.TM.". Freebond.TM. thermoplastic exists in
solid form at room temperature (about 70.degree. F.), and changes
into a non-solid liquefied state when heated to a temperature of
approximately 122.degree. F. Preferably, the conformable substance
24 comprises a mixture of Freebond.TM. thermoplastic and one or
more other more thermally-conductive materials in order to enhance
the thermal-conductivity of the substance, and in turn decrease the
cycle times required to heat the substance from the solid to the
non-solid form, and cool the substance from the non-solid to the
solid form.
[0021] Accordingly, in the currently preferred embodiment of the
invention, the selectively conformable substance 24 consists of
Freebond.TM. thermoplastic and aluminum powder mixed in accordance
with the following ratio: approximately 3.5 parts aluminum powder
to approximately 1 part Freebond.TM. thermoplastic by weight. The
aluminum powder is composed of approximately 20 micron spherical
particles; however, other sizes and/or types of
thermally-conductive additives may equally be employed. This
preferred mixture has significantly improved thermal-conductivity,
and therefore shorter heating and cooling cycle times in comparison
to the Freebond.TM. thermoplastic itself. However, if desired, the
metallic powder or other thermally-conductive additive may be
eliminated, or different relative amounts of thermoplastic and
conductive particles may be employed depending upon the specific
thermal conductivity and/or other physical characteristics desired.
In addition, although the Freebond.TM., or like thermoplastic is
preferred, those skilled in the pertinent art may recognize based
on the teachings herein that other thermoplastics may be employed.
In addition, those skilled in the pertinent art may recognize based
on the teachings herein that the selectively conformable substance
24 is not limited to the thermoplastic-types described, but may
encompass other substances that are readily changeable between
solid and non-solid forms by the application of, for example, heat,
radiation, chemical or mechanical energy.
[0022] In the conformable lap assembly 10, the substance 24 is
selectively changed between its solid and non-solid forms by a
temperature-controlled fluid, preferably water, coupled in thermal
communication with the base surface 18 of the lap to control the
temperature of the base surface and, in turn, control the
temperature of the substance 24 in thermal communication with the
base surface. As shown in FIG. 1, the lap mount 14 includes at
least one fluid channel 26 connected in fluid communication with a
temperature-controlled fluid source 28. During set up, the
conformable lap 12 is fixedly secured to the lap mount 14, as shown
in FIG. 2 and described further below, and the fluid source 28 is
actuated to direct the temperature-controlled fluid, preferably
water, through the conduit 26 and onto an underside 30 of the base
surface 18. As shown in FIG. 1, the underside 30 of the base
surface 18 is convex shaped and defined by a first radius "r1". A
discharge end 31 of the fluid channel 26 is spaced immediately
below the approximate center of the underside 30, and as indicated
by the arrows 32, 34 in FIGS. 1 and 3, the temperature-controlled
fluid flows onto the convex surface of the underside 30 to rapidly
contact and either heat or cool the entire surface, respectively.
The lap base 16 (or at least the portion defining the base surface
18) is formed of a material having relatively high thermal
conductivity, such as aluminum, in order to decrease the heating
and cooling cycle times of the lap.
[0023] Referring to FIGS. 1 and 2, the fluid channel 26 includes a
hot fluid pipe 35 and a cold fluid pipe 36, substantially
concentric with the hot fluid pipe 35. Referring to FIG. 3, the
discharge end 31 of the fluid channel 26 includes at 0 least one
hot fluid opening 37 and a plurality of cold fluid openings 38, 39.
The hot fluid opening 37 is in communication with the hot fluid
pipe 35 and is substantially centrally located such that the hot
fluid 32 is directed approximately toward the center of the
underside surface 30, as also indicated by arrows 32 in FIGS. 1 and
2. The hot fluid disperses and heats the surface 30. The cold fluid
openings 38, 39 are in fluid communication with the cold fluid pipe
36 and are directed toward the center of the underside surface 30
and toward outer sides of the surface 30 such that the cold fluid
34 cools the underside surface 30. In the preferred embodiment of
the present invention, the cold fluid openings 38 are formed at a
substantially 45.degree. (forty-five degree) angle. As seen in FIG.
1, fluid drain 42 is coupled through at least one drain pipe 44 to
receive and dispose of (or, if desired, re-circulate) the
temperature-controlled fluid after passage through the interior of
the lap mount. The drain pipe 44 is substantially concentric with
the hot and cold fluid pipes 35, 36.
[0024] In the preferred embodiment of the invention, the
conformable substance 24 is changed into its non-solid form by
introducing relatively hot water at a temperature T1 through the
discharge end of the conduit 26 to thereby heat the base surface 18
and the layer of conformable substance 24 to approximately the same
temperature. Thus, for the Freebond.TM. type substance 24 described
above, the temperature T1 should be at least approximately
122.degree. F. This fluid temperature is sufficient to rapidly
heat, and in turn change the preferred substance 24 from its solid
to non-solid form. In the preferred embodiment, water at
approximately 150.degree. F. directed through the discharge end of
the conduit 26 changed the preferred substance 24 from its solid to
non-solid form within about 10 to 15 seconds. Then, after
conforming the work surface 22 to the curvature of a selected
optical surface, as described further below, water at temperature
of approximately 40 to 50.degree. F. directed through the discharge
end 31 of the conduit 26 changed the preferred substance 24 from
its non-solid to its solid form within about 5 to 10 seconds.
[0025] The present inventors have discovered that any deflection in
the work surface 22, or any relative movement between the work
surface and the layer of conformable substance 24 should be
minimized, and preferably eliminated, in order to produce finished
lenses of sufficient optical quality. Accordingly, the work surface
22 is made of a relatively thin, hard and stiff material in order
to minimize, and preferably eliminate any deflection of the work
surface during finishing operations. In the currently preferred
embodiment of the invention, the work surface 22 is made of a thin
polymeric material, preferably vinyl, having a thickness within the
range of approximately 4 to 8 mils. This, in combination with the
properties of the preferred Freebond.TM.-type substance 24,
substantially prevents any deflection in the work surface 22 and
relative movement between the work surface and the layer 24.
[0026] As shown best in FIG. 1, the depending flange 20 of the lap
base 16 has a peripheral groove 46 for receiving the polymeric
sheet of the work surface 22 and an elastomeric o-ring 48 overlying
the sheet within the groove. During assembly, the polymeric sheet
forming the work surface 22 is superimposed over the layer of
conformable substance 24, and pulled downwardly about the depending
flange 20 of the lap base 16. Then, the elastomeric o-ring 48 is
rolled or otherwise slipped over the flange 20 and received within
the peripheral groove 46 to fixedly secure the polymeric sheet to
the lap. The elastomeric ring 48 is dimensioned to form a
sufficiently tight fit within the groove 46 to fixedly secure the
polymeric sheet to the lap throughout set up and finishing
operations. As will be recognized by those skilled in the pertinent
art based on the teachings herein, other mechanisms or structures
may equally be employed to fixedly secure the work surface 22 to
the lap base 16. For example, the sheet forming the work surface 22
could be attached to the lap by an adhesive, by welding, or by any
of numerous known fasteners for fixedly securing the sheet to the
base.
[0027] As shown in FIG. 4, a finishing pad 50 is superimposed on,
and attached to the work surface 22 to further define the work
surface for finishing eyeglass lenses. The finishing pad 50 may be
formed in accordance with any of numerous known finishing pads
which are commercially available for fining and/or polishing
optical surfaces. Accordingly, the finishing pad 50 may have an
abrasive material, such as a silicone carbide grit, bonded or
otherwise integrated into the pad to form the work surface for
fining the selected optical surface. An exemplary finishing pad is
provided in the form of a slotted disk, and may be of the type
disclosed in U.S. Pat. No. 4,255,164 to Butzke et al. For
polishing, on the other hand, the pad 50 may be in the form of a
fibrous finishing pad without abrasives (e.g., a non-woven fabric,
such as felt) which may be used with a slurry, if necessary,
introduced at the interface of the optical and work surfaces.
[0028] The finishing pad or like work surface 50 is superimposed
on, and attached to the work surface 22 by any of numerous means
for attaching or joining known to those of ordinary skill in the
pertinent art. Preferably, the finishing pad 50 is attached to the
underlying work surface 22 by an adhesive, or a double-sided
fastening tape, which fixedly secures the finishing pad in place
and prevents any relative movement between the pad and underlying
surface during finishing operations. Preferably, the conformable
lap 12 includes means for interchangeably attaching the finishing
pad or like member 50 to the underlying work surface 22. For
example, the underside of the finishing pad 50 may include a
double-sided adhesive or other fastening tape (e.g., Velcro.TM.),
or other means for fastening or joining and permitting the
finishing pad to be attached to, and detached from the underlying
work surface 22 without tools. As an alternative to the finishing
pad 50, the work surface 22 may define the desired surface
characteristics for finishing an optical surface. However, the
interchangeable finishing pads 50 are currently preferred.
[0029] As shown in FIGS. 1 and 2, the lap assembly 10 further
includes means for detachably mounting the conformable lap 12 to
the lap mount 14. The lap mount 14 has an upstanding flange 52
which is dimensioned to be slidably received within the depending
flange 20 of the lap base 16. The upstanding flange 52 defines a
peripheral groove 54 receiving an elastomeric o-ring 56. The
depending flange 20 of the lap base 16 similarly defines an annular
groove 58 on its interior surface which is aligned with the
peripheral groove 54 when the conformable lap 12 is seated on the
mount 14. The peripheral groove 54 is coupled in fluid
communication by a conduit 60 to a pressure/vacuum source 62. In
order to fixedly secure the conformable lap 12 to the lap mount 14,
the pressure/vacuum source 62 is actuated to introduce pressurized
gas, preferably air, into the conduit 60 which, as indicated in
broken lines in FIG. 1, pushes the elastomeric ring 56 outwardly
and into the annular groove 58 of the lap base 16 to thereby lock
the conformable lap to the mount. Then, in order to release the
conformable lap 12 from the mount 14, the pressure/vacuum source 62
is actuated to draw vacuum through the conduit 60 which, in turn,
draws the elastomeric ring 56 inwardly away from the annular groove
58 of the lap base 16. With the vacuum source actuated, the
conformable lap 12 may be easily lifted away from the mount 14.
[0030] In FIG. 4, the conformable lap assembly 10 is mounted in an
apparatus for finishing the contoured optical surface of an
eyeglass lens blank 66. In this type of apparatus, the lens blank
66 is joined by an adhesive, mechanical fastener, or other suitable
joining mechanism to a mounting bracket or lens holder 68 located
within a tub or like receptacle (not shown) for performing the
finishing operations. Preferably, the lap mount 14 is fixedly
secured to a support surface of the apparatus with the lens holder
68 and lens 66 supported above the conformable lap 12. As shown in
FIG. 3, the work surface 22 of the conformable lap 12 defines a
diameter less than the diameter of the optical surface 64 in order
to permit the work surface to adopt the signature (i.e., conform to
the curvature) of the optical surface.
[0031] The lens holder 68 is driven by a suitable drive system 70
along a predetermined path in accordance with commands issued by a
controller 72. The controller 72 is electrically connected to each
of the components of the assembly, including the fluid source 28,
the pressure/vacuum source 62 (shown in FIG. 1) and the drive
system 70, in order to automatically control each component for
performing the set up and finishing operations. The path of the
lens 66 and lens holder 68 may be orbital, as described in U.S.
Pat. No. 3,893,264, or may have a linear, arcuate or other desired
configuration. Preferably, however, the path is defined by the
curvatures of the selected lens surface in order to accurately
reproduce the curvatures in the finished lens.
[0032] FIG. 4 illustrates an exemplary apparatus for finishing an
optical surface in this manner and is disclosed in U.S. patent
application Ser. No. 09/073,491, filed on May 6, 1998, entitled
"Method and Apparatus for Performing Work Operations on a Surface
of One or More Lenses", which is assigned to the Assignee of the
present invention, and is hereby expressly incorporated by
reference as part of the present disclosure. In this apparatus, the
drive system 70 comprises at least three pairs of articulated
supports 74, which are angularly spaced relative to each other, and
connected to the lens holder 68 for moving the lens holder and lens
in virtually any predetermined direction under commands issued by
the controller 72 to set up the conformable lens and finish the
optical surface, as hereinafter described.
[0033] In the operation of the present invention, the apparatus of
FIG. 4 is set up to finish a selected lens 66 by fixedly mounting
the lens to the lens holder 68. Then, the conformable lap 12 is
prepared to conform to the curvature of a selected lens surface 67
of the selected lens 66. First, with the lens 66 spaced above the
work surface 22 of the lap, the controller 72 actuates the fluid
source 28 to introduce relatively warm water at the temperature T1
through the discharge end 31 of the fluid channel 26, FIG. 2, and
into contact with the underside 30 of the lap base 16. As described
above, in the preferred embodiment, water at approximately
150.degree. F. may change the Freebond-type substance 24 from its
solid to non-solid form within several seconds. Then, with the
layer of selectively conformable substance 24 in its non-solid
form, the control computer 72 actuates the drive system 70 to move
the lens holder 68 downwardly, and in turn press the lens surface
67 into contact with the work surface 22, as shown in FIG. 5.
Because the intermediate layer 24 is in its non-solid form, the
work surface 22 is permitted to exactly conform to the curvatures
of the optical surface 64. Referring to FIG. 5, as the lens 66 is
pressed into contact with the work surface 22 of the lap, the
conformable substance 24 is redistributed forming a relatively
thinner layer in the center portion thereof.
[0034] Once the optical surface 67 is pressed into conforming
contact with the work surface 22, the control computer actuates the
fluid source 28 to introduce relative cool fluid through the
discharge end 31 of the conduit 26 and into contact with the side
portions of the underside 30 of the base surface 18 to change the
layer of conformable substance 24 from its solid to non-solid form.
As described above, in the currently preferred embodiment, water at
a temperature of approximately 40 to 50.degree. F. may change the
preferred substance 24 from its non-solid to solid form within
several seconds. As the cool fluid 34 initially comes into contact
with the side portions of the surface 30, cooling of the side
portions begins first in order to ensure that thicker layer of the
redistributed conformable substance 24 is adequately cooled and
that the conformable lap accurately assumes the shape of the lens
surface 67.
[0035] With the layer of conformable substance 24 in its solid
form, and thus the work surface 22 locked in the position
conforming to the curvature of the selected optical surface, the
drive system 70 is actuated to move the lens holder 68 away from
the conformable lap 12 to thereby release the lens 66 from the lap.
If necessary to facilitate removal of the lens 66 from the work
surface 22 due to vacuum created between the lens and lens surface,
a fine thread may be interposed between the lens and work surface
prior to formation of the work surface curvatures to prevent the
formation of any vacuum. Any indentation created by the fine thread
will not affect performance of the lap.
[0036] Once the lens is removed from the work surface 22, the
finishing pad 50 is superimposed on, and attached to the work
surface in a manner as described above for fining and/or polishing
the optical surface. Because the work surface 22 defines the
curvatures of the selected optical surface 67, the finishing pad 50
slightly changes the curvatures. In order to accurately reproduce
the selected curvatures in the finished lens, the lens is placed
onto the pad 50 for slightly reconforming the conformable substance
24. Thus, the conformable substance is reconformed to compensate
for the thickness of the pad 50. In the preferred embodiment,
compensating for the thickness of the pad does not require a full
cycle of changing the conformable substance 24 from its solid to
non-solid form. Also, water is directed onto the pad.
[0037] The controller 72 then actuates the drive system 70 to move
the lens holder 68 and lens 66 mounted thereon into contact with
the finishing pad 50, and in turn move the lens holder and lens
through the predetermined drive path to create relative movement at
the interface of the lens surface 67 and finishing pad 50 to
thereby finish the lens. The finishing pad 50 may initially take
the form of a conventional fining pad to fine the optical surface.
Then, when the fining is complete, the fining pad 50 may be removed
from the work surface 22 and replaced with a conventional polishing
pad to polish the optical surface 67. Once the finishing operations
are complete, the pads may be discarded, and the operations
repeated for another lens.
[0038] The present inventors have discovered that it may be
desirable to provide a plurality of conformable laps, wherein each
lap defines a different nominal ophthalmic lens curvature. In
addition, the nominal curvature in combination with the thickness
of the layer of conformable substance 24 is set for each lap 12 to
accommodate a plurality of different ophthalmic lens curvatures
within a respective predetermined range of curvatures. One
advantage of providing a group of laps in this manner is that the
thickness of the layer of conformable substance 24 may be reduced
in comparison to a single lap designed to accommodate a broader
range of ophthalmic lens curvatures. As a result, the heating and
cooling cycles times may be reduced, and to a lesser extent, the
effect of any shrinkage in the layer of conformable substance upon
transition from the non-solid to solid form may be minimized.
[0039] In the currently preferred embodiment of the invention, a
family of different laps of the type shown in FIGS. 1-5 can be
provided in order to accommodate a range of different lens
curvatures from approximately 0 to 20 diopters ("D"). In this case,
each conformable lap 12 is designed to accommodate an approximately
1.5 (one and a half) diopter range of lens curvatures as
follows:
1 LAP NO. RANGE OF CURVATURE 1 0-1.5 D 2 1.5 D-3 D 3 3 D-4.5 D 4
4.5 D-6 D 5 6 D-7.5 D 6 7.5 D-9 D 7 9 D-10.5 D 8 10.5 D-12 D 9 12
D-13.5 D 10 13.5 D-15 D 11 15 D-16.5 D 12 16.5 D-18 D 13 18 D-19.5
D 14 19.5 D-21 D
[0040] In this currently preferred embodiment, each conformable lap
12 can handle a range from nominal to -1.5 (negative one and a
half) diopters and achieve the approximate heating and cooling
cycle times set for the above. Each lap can also accommodate a
cylinder on the order of a 1.5 (one and a half) add (e.g.,
-4.5.times.6 on a 6D lap (Lap No. 4 above)). In addition, the
cylinder need not be symmetrical about the mean of the add, but
rather the total add may be to one side of the nominal curvature.
Accordingly, the family of 14 (fourteen) conformable laps
summarized above may conform to and finish any lens curvature up to
21 diopters (with as much as a 1.5 add). Additionally, some lenses
require a cylinder or cross curve in addition to the base curve.
The lap could have some preset amount of cylinder curve.
[0041] However, as will be recognized by those skilled in the
pertinent art based on the teachings herein, the nominal curvatures
set forth above, and the predetermined range of curvatures for each
conformable lap are only exemplary, and may be changed as desired
depending upon any of a variety of factors, including the desired
heating and cooling cycle times.
[0042] Additionally, in the preferred embodiment of the present
invention, the working surface of the conformable lap is smaller
than the diameter of the lens to be polished. As is known in the
art, for higher diopter laps, a special high diopter lap or raised
lap is used.
[0043] As will be recognized by those of ordinary skill in the
pertinent art, numerous changes and modifications may be made to
the above-described and other embodiments of the invention without
departing from its scope as defined in the appended claims.
Accordingly, this detailed description of preferred embodiments is
to be taken in an illustrative, as opposed to a limiting sense.
* * * * *