Note: Descriptions are shown in the official language in which they were submitted.
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LENS BLOCK AND ASSOCIATED DE-BLOCKING
APPARATUS AND METHOD
FIELD OF THE INVENTION
This invention relates generally to the mounting of ophthalmic lens blanks and
ophthalmic lenses to a lens block for support during a~lens surfacing
operation, and
the removal of a lens from a lens block after lens surfacing.
BACKGROUND OF THE 11~TVENTION
A traditional way to bond a lens blank to a lens block is through the use of a
meltable adhesive substance such as wax. While waxes are a reasonably workable
bonding agent, there are detriments to their use. Wax tends to be messy both
in its
inj ection and its removal. Wax tends to leave residue on the lens blank,
requires
considerable time to cool sufficiently to set (on the order of 15 minutes) and
the heat
imparted to the lens and stresses associated with setting may cause optical
defects
in the finished lens through associated warpage.
More recently adhesive compounds for lens blocking have been developed
which are curable by exposure to ultra violet ("UV") and visible radiation
rather than
thermosetting. While such UV curable compounds have beneficial properties as
compared to wax, they however present their o'vn challenge with respect to
stripping.
Many of these compounds incorporate an agent that responds to a solvent to
assist in
softening the adhesive for deblocking. Such agents are however undesirable as
typically they require considerable time to effect deblocking. Also, such
agents may
be susceptible to liquid lubricants used in the lens surfacing operation(s).
A common method for deblocking a lens mounted with a wax is to place the
lens in a cylindrical tube which receives the lens block and engages a
perimeter of the
lens. The tube is then struck against a hard surface with the lens block
facing the
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surface. The tube prevents the movement of the lens toward the surface while
allowing the momentum of the lens bloclc to separate it from the lens.
While using a tube in the traditional deblocking method to deblock a UV
compound mounted lens may work as long as the adhesion isn't overly great, a
problem arises when there is insufficient mass in the block to provide
adequate
momentum. Conventional blocks were typically of metal. In order to cure a UV
curable compound, it is desirable to use a UV transmissive plastic lens block.
Obviously a plastic lens block will have significantly less mass than a metal
one of
similar dimensions.
It is an object of the present invention to provide a deblocking apparatus
("deblocker") aneT method which enables rapid deblocking without reliance upon
inertial forces of the lens support for providing the deblocking force.
It is a further object of the present invention to provide a lens block for
use
with UV curable lens mounting compounds that provides even curing of the UV
curable compounds.
It is a further object of the present invention to provide a radio frequency
transmissive lens block enabling the use of an embedded RFID tag in a lens
block.
SUMMARY OF THE INVENTION
A lens block is provided for blocking an ophthalmic lens. The lens block has
a body with a base, a lens support surface opposite the base and engagement
means
for engaging a clamping means for securing the block to a deblocking
apparatus. At
least one passage extends through the body and fluidly communicates with the
lens
support surface. The block is of a material transmissive to radiation having a
wavelength suitable for curing a radiation curable compound for use in lens
blocking.
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The engagement means may be a groove at least partially encircling the body
generally parallel to the base.
In one embodiment the passage extends between the base and the lens support
surface.
A deblockillg apparatus is provided which has a housing with a receptacle for
receiving a lens block. Releasable clamping means are associated with the
housing
to engage the lens block to secure the lens block to the receptacle. The
apparatus has
a fluid outlet for registering with a fluid passage inlet in the lens block.
The apparatus
further has a pump with a pump inlet for receiving a deblocking fluid, the
pump fluidly
communicates with the fluid outlet for supplying pressurized fluid to the
outlet. A
fluid controller is provided to control flow of~the deblocking fluid to the
fluid outlet
and a fluid seal is provided to effect a seal between the fluid outlet and the
fluid
passage inlet.
Preferably the deblockiilg apparatus has a cover attached to the housing for
covering a lens mounted to the block during deblocking, the cover being
movable
between an open position allowing placement and removal of the lens block and
a
closed position for shielding an operator from the lens and the deblocking
fluid. A
latch is provided for releasably securing the cover in the closed position.
The cover may operably engage the clamping means to move the clamping
means from a released configuration to an engaged configuration as the cover
is
moved from the open position to the closed position. The cover preferably has
a lens
impact damper which registers with the lens in the closed configuration to
limit
displacement of the lens away from the lens block.
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The clamping means may include at least one latterly swingable j aw pivotably
connected to one of a housing and the receptacle and having a inwardly
extending
ridge for registering with the groove in the lens block. Each jaw may have a
cam
surface for registering with a corresponding cam surface on the cover to cause
the
jaw to urge the ridge toward the groove in response to the cover being urged
toward
the closed position.
The ridge and the recess maybe provided with corresponding tapered surfaces
which cause the lens block to be urged towards the receptacle as the ridge is
urged
into the recess.
The deblocking fluid may be water. The pump may be pneumatically operable
and the pump may supply pulses of water to the fluid outlet. The fluid
controller may
be a valve which controls the flow of pressurized air to the pump.
The lens block may have a groove extending into the lens mounting surface and
encircling the fluid outlet.
An identifying tag may be imbedded in the lens block for providing encoded
data as to the lens mounted to the lens block, the data being transmitted
through the
lens block.
The identifying tag may be an RF ID ("Radio Frequency Identification Tag")
tag.
The lens block may include orientation indices for alignment of the lens block
with a chuck of a lens generating machine. .
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5 The passage may slidiiigly receive a piston immediately adjacent the lens
support surface, the piston being axially displacable by fluid pressure within
the
passage to extend from the lens support surface.
The piston may have a lens mounting surface facing away from the lens block
which, in a retracted position of the piston is substantially flush with the
lens support
surface.
The piston may include an alignment indicator for indicating lens orientation
and the piston and the passage adjacent the piston may be configured to
axially orient
the piston within the lens block.
The configuration for axially orienting the piston within the lens block may
be
by way of having the piston and the passage respectively shaped to register
with each
other in a fixed axial orientation.
The lens block may also have optical features such as a Fresnel lens formed
in ~a bottom surface thereof to improve uniformity of light intensity on the
UV
curable compound.
The lens block may be translucent rather than transparent to cause at least
some diffusion of light passing therethrough during curing of a lens mounted
thereto
to reduce shadowing.
The translucence may be derived by a surface finish of the lens block.
A method is provided for deblocking a lens from a lens block comprising the
step of:
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(i) applying pressurized fluid through a lens block to an interface between a
lens
mounting face on the lens block and an adhesive securing the lens to the lens
mounting face.
A method of deblocking a lens from a lens block comprising the step of:
(ii) applying pressurized fluid to a fluid pressure responsive piston mounted
between the lens and the lens block to cause the piston to urge the lens away
from the lens block
In either method the deblocking fluid may be water and the method may
include the further steps of:
(iii) mounting a damper adjacent to the lens to limit movement of,the lens
away
from the lens block during deblocking; and,
(iv) shielding the lens block and the lens during de- blocking.
DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention are described below with
reference to the accompanying illustrations in which:
Figure 1 is a perspective view of a deblocker according to the present
invention;
Figure 2 is a plan view from above of the deblocker of Figure 1 ' in an open
configuration;
Figure 3 is a section on line 3-3 of Figure 2;
Figure 4 is an enlargement of the encircled area identified by reference E in
Figure 3;
Figure S is a plan view from above of the deblocker of Figure 1 in a closed
configuration;
Figure 6 is a section on line 6-6 of Figure 5;
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Figure 7 is an enlargement of the encircled area F in Figure 6;
Figure ~ is a perspective view from below of an alternate embodiment of a
lens block according to the present invention;
Figure 9 is a view corresponding to Figure ~ but indicating in dashed lines a
fluid passage and a passage for receiving an RFID tag;
Figure 10 is a bottom plan view of the lens block of Figure ~;
Figure 11 is a view corresponding to~Figure 10 but showing in dashed outline
internal features not visible in Figure 10;
Figure 12 is an elevation of a lens block according to the present invention;
Figure 13 is a view corresponding to figure 12 but showing internal details in
dashed outline;
Figure 14 is an exploded perspective view of a further alternate embodiment
lens block according to the present invention;
Figure 15 is a view corresponding to Figure 14 but showing internal details in
dashed outline;
Figure 16 is a section on line I6-16 of Figure 15;
Figure 16A is a bottom plan view of the lens block of Figure 14;
Figure 16B is a section on line 16B-16B of Figure 16A;
Figure 16C is a perspective view from below of the piston portion of the lens
block of Figure 14;
Figure 17 is an exploded perspective view of yet another embodiment of a lens
block according to the present invention;
Figure 18 is a view corresponding to Figure 17 but showing internal details in
dashed outline;
Figure 19 is a section on line 19-19 of Figure 18;
Figure 20 is a bottom elevation of the lens block of Figure 17;
Figure 21 is a section on line 21-21 of Figure 20;
Figure 22 is a perspective view of the piston portion of the lens block of
Figure 17;
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g.,.
Figure 23 is a perspective view of the bottom of a lens block according to the
.
present invention including a Fresnel lens ~ as an optical feature for
diffusing light
being shone therethrough;
Figure 24 is a bottom elevation corresponding to Figure 23;
Figure 25 is a section on line 25-25 of Figure 24;
Figure 26 is a bottom perspective of an embodiment of a lens block according
to the present invention incorporating a curved bottom face as a feature for
diffusing
light during lens curing;
Figure 27 is a bottom elevation corresponding to Figure 26;
Figure 28 is a section on line 28-28 of Figure 27;
Figure 29 is a.bottom view of a lens block configuration similar to that of
Figure 23 but showing a more extensive Fresnel surface;
Figure 30 is a bottom elevation of the lens block of Figure 29;
Figure 31 is a section on line 31-31 of Figure 30; and,
Figure 32 is a schematic sectional view illustrating diffusion of light
through
a lens block having a planar base.
DESCRIPTION OF PREFERRED EMBODIMENTS
A deblocker according to the present invention is generally identified by
reference 10 in the accompanying illustrations. A lens block for use in
association
with the deblocker 10 is generally identified by reference 100.
. The lens block 100 has a body 102 with a base 104, a lens support surface
106
opposite the base 104 and engagement means in the form of a groove 108
extending
around the body 102. The groove 108 engages clamping means on the deblocker 10
in a manner which is described in more detail below
A fluid passage 110 extends through the body 102 of the block 100 to provide
a fluid conduit through the block 100 to the lens support surface 106. In the
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illustrated configuration the fluid passage 110 extends between the base 104
and the
lens support surface 106. It will however be appreciated that this is not
essential
other than to provide a fluid inlet into the passage 110 which registers with
a fluid
outlet in the deblocker 10. Accordingly it may be possible to reconfigure the
block
100 and the deblocker 10 to provide for a fluid inlet into the passage 110
other than
through the base 104.
The lens block 100 may additionally have orientation indices such as holes
120 or a flattened portion about the base 122 to rotationally orient the block
with a
chuck of a lens surfacing machine.
The body 102 is preferably of a material such as a plastics material which is
transnussive of light energy in the UV and visible wavelengths, assuming of
course
that it is desired to cure a W curable lens mounting adhesive through the
block 100.
Other materials may be considered for radiation curable compounds which cure
with
radiation out of the UV and visible wavelengths.
In practice it has been found that a lens block 100 is preferably translucent
rather than entirely transparent. This is because the rate and degree of
curing of W
curable lens blocking adhesives is effected significantly by the intensity of
light in
any given xegion of the adhesive. Accordingly any shadowing effect tends to
cause
anomalies which will eventually affect lens surface quality in subsequent lens
surface
generation.
~ A translucent rather than a transparent lens black causes diffusion of the
light
thereby more evenly distributing the light throughout the lens block and
minimizing
any shadowing effect and thereby effecting a more even cure. Translucence may
be
achieved through any of the various known processes such as applying a
translucent
finish, molding the lens block with a textured surface, sandblasting to
"roughen up"
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5 the surface or the addition of suitable light dispersing media in the raw
materials from
which the lens block is formed.
It is possible also to improve the uniformity of light intensity on, the UV
compound by incorporating suitable optical features in the lens block. For
example,
as illustrated in Figures 23 through 25 the lens block 100 may incorporate a
Fresnel
10 lens shown at reference 150 in its base 104. A further Fresnel lens may be
incorporated higher up on the base as shown as reference 152 in Figures 29
through
31. Other configurations may also be possible however a Fresnel lens is
advantageous
in that it does not substantially effect the depth of the lens block 100 or
its ability to
rest on a flat surface.
Other optical features are possible. One such feature is illustrated in
Figures
26 through 28. Instead of a Fresnel lens, a simple lens 160 is formed into the
base
104. The fusion of light by the simple lens 160 is illustrated in Figure 28.
The optics of the block 100 should preferably be optimized based on the lens
curvature is covered by a particular block. The base curve of the lens
mounting
surface 106 may be varied depending on the range of lenses to be supported
thereby.
The improvement of incorporating a Fresnel lens 150 or other features to
improve uniformity of light intensity on the LTV compound may be adapted to
transparent lens blocks 100 which lack the present deblocking arrangement. For
example, it is expected that improved results would be obtained also with UV
curable
compounds of the solvent strippable kind.
A lens 200 is illustrated as being mounted to the lens mounting face 106 by
an adhesive which is not shown but which would occupy a space 202 between the
lens
200 and the mounting face 106.
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The deblocker 10 has a housing 12 to which is mounted a receptacle 14 for
receiving the lens block 100. Clamping means in the form of a block clamp 16
are
provided adj acent the receptacle 14 and may, as illustrated include a fixed
part 18 and
a laterally swingable jaw 20 pivotally connected thereto at a pivot 22 for
movement
about the pivot 22 is a direction illustrated by arrows 24. The jaw 20 is
movable
between a released configuration shown in Figures 1 through 4 and an engaged
configuration shomi in Figures 5 through 7.
The fixed part 18 and tie j aw 20 have respective inwardly extending ridges 30
and 32 for registering with the groove 108 of the block 100. Preferably the
ridges
30 and 32 have respective cam surfaces 34 and 36 which register with a
corresponding cam surface 112 of the groove 108 to urge the block toward the
receptacle 14 in response to the jaw 20 being urged toward the fixed part 18.
It will be appreciated that it is not necessary for the groove 108 to
completely
encircle the block 100. For example a pair of shorter grooves maybe provided
and
the ridges 30 and 32 maybe comparatively shorter. Other clamping means may
also
be utilized which have the desired effect of securing the block 100 to the
receptacle
14, for example the block 100 could threadedly engage the receptacle 14 or be
provided with downwardly extending prongs which are grasped by suitably
configured
pincers associated with the receptacle 14.
It will further be appreciated that the clamping means may include more than
one jaw 20 and that each jaw 20 may be operably connected to the cover 80 in
such
a manner as to release and engage in response to movement of the cover 80 so
as to
avoid having to swing the jaw 20 as a separate step before closing the cover
80.
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The deblocker 10 further has a fluid delivery port 40 with a fluid outlet 42
which registers with a fluid inlet 114 into the fluid passage 110. A seal in
the form
of an 'O' ring 44 may be provided about the outlet 42.
A pump 5 0 which may, as illustrated in Figure 1 be mounted within the housing
12 fluidly communicates with the fluid outlet 42 through the fluid delivery
port 40.
The pump 50 has an inlet 52 which receives a deblocking fluid.
The deblocking fluid may be water or another suitable incompressible fluid.
Compressible fluids such as air might also be utilized however they tend to
impart an
undesirable projectile force on the lens 200 upon deblocking. Incompressible
fluids
seem to yield more easily controllable results. The fluid may be stored in a
reservoir
70 having an outlet 72, and an ililet 74.
Although the pump 50 may be manually or electrically operable, in the
illustrated embodiment, an air operatedpump 50 is utilized and receives
compressed
air from an air inlet 56 connected to a valve block 58 and controlled by a
push button
60. The valve block 58 acts as a controller for controlling actuation of the
pump 50
and therefore also acts to control flow of deblocking fluid to the fluid
outlet 42.
In use, a lens block 100 with a lens 200 affixed thereto is secured to the
receptacle 14 by the clamping means 16 with the fluid inlet 114 registering
with the
fluid outlet 42 and the base 104 sealingly engaging the receptacle 14 by
virtue of the
O ring 44. The pump 50 is energized and draws fluid into the pump inlet,52
pressurizes and discharges it through the fluid port 40 and through the fluid
outlet 42.
The pressurized fluid enters the fluid passage 110 in the block 100 and passes
it to
the lens support surface. The pressurized fluid then causes separation between
the
lens support surface 106 and the adhesive to deblock the lens 200.
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' In practise it has been found beneficial to supply the fluid from the pump
50
in short "bursts" or "pulses" rather than under a continuous pressure. It has
also been
found beneficial to provided a shallow groove 116 extending into the lens
support
surface 106 and encircling the fluid passage 110 to avoid fluid escaping to
one side
rather than effecting total deblocking. It has also been found that a
plurality of non-
centralized fluid passages 110 provide consistent deblocking without having a
groove
116. Presumably the combination of a plurality of fluid passages 110 and a
groove
116 would also work however this may be somewhat redundant.
In order to capture the lens 200 when it debloclcs and also to avoid
deblocking
fluid from spraying out from around the receptacle, 14, a cover 80 is provided
which
may be hingedly attached to the housing 12. The cover 80 is movable between an
open position as shown in Figures 1 through 4 and a closed position shown in
Figures
5 through 7. In the open position, the cover 80 allows placement of the lens
block
100 and lens 200 on the receptacle 14. In the closed position, the cover , the
lens
200 and lens block 100 to shield an operator from the lens 200 and the
deblocking
fluid.
The cover 80 may include a frusto-conical cam surface 82 which acts against
a corresponding cam surface 26 on the jaw 20 to urge the jaw 20 toward its
engaged
position in response to a closing force being applied to the cover 80.
The cover 80 may have a latch 82 operated by a handle 84 for engaging the
housing 12 to maintain the cover 80 in its closed position.
To avoid damage to the lens 200 which might otherwise occur by the lens 200
being hurled against the cover 80 upon deblocking a lens impact damper 86 is
provided within the cover 80 in a location which registers with the lens 200
when the
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cover 80 is closed. The lens impact damper may be a resilient member extending
between the cover 80 and the lens 200.
Although the deblocker 10 may be operated as a total loss system with respect
to fluid usage, preferably the deblocking fluid will be captured and returned
to the
reservoir 54. This may be accomplished by providing a drain 56 in the top of
the
housing 12 and a drain outlet 60 from the housing 12 which fluidly
communicates
with the inlet 74 into the reservoir 704. Recirculation may be gravity or pump
assisted as required. Alternatively, the housing 12 itself can be configured
to act as
a sump.
In order to avoid passage of lens mounting adhesive into the passage 110 in
the
lens block 100 during blocking, a removable blanking pin (not shown) may be
used
to fill the passage 110 during blocking.
An advantage to using a plastic lens block 100 is in lens identification. As
plastics are transmissible to radio frequency signals, an RF marker (or "RFIl?
tag")
300 containing encoded information including an identification code and
possibly
other information on such things as lens orientation, type and shape may be
embedded
in the lens block 100. Conventional metal blocks will not transmit radio
frequency
signals. A receptacle 302 is illustrated extending into the lens block 100 for
receiving the RFID tag 300.
Figures 14 through 16 illustrate an alternate embodiment of a lens block
according to the present invention. Figures 17 thxough 22 illustrate yet
another
alternate embodiment of a lens block according to the present invention. As
most of
the features of the t<wo alternate embodiment lens blocks axe common to the
lens
block 100 described above, like components are numbered with like reference
numerals and the above description applies.
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5 The principal difference between the two alternate embodiment lens blocks
100 and the lens block described above is in the mounting of a fluid
responsive piston
140 in the fluid passage 110 adjacent the lens mounting surface 106
As illustrated in Figures 14 through 19, the passage 110 has a bore 130 at an
end opposite the inlet 114 which slidingly receives the piston 140 immediately
10 adjacent the lens support surface 106. The piston 140 is axially displaced
along the
bore 130 by fluid pressure along the passage 110 to cause it to extend above
the lens
support surface 106.
The piston 140 has a lens mounting surface 146 which, in a retracted position
illustrated in Figures 16 and 19 substantially flush with the lens support
surface 106
15 adjacentthereto.
In use, the piston portion 140 of the lens mounting block 100 is inserted
lllt0
the bore 130 of the body 102. A lens 200 (not illustrated in Figures 9 through
19)
is mounted to the lens mounting block 100 as described above in the previous
embodiment using suitable lens mounting adhesives.
In order to deblock the lens 200, a similar method to that described above is
employed namely, pressurized fluid is introduced into the fluid passage 110.
Unlike
the above description, deblocking is not merely a function of pressurized
fluid acting
directly against the lens 200 but instead, the fluid acts to a large extent
against the
piston 140 causing it to move axially along the bore 130 toward the lens 200
to press
the lens off of the lens support surface 106. Some fluid will likely escape
between
the piston 140 and the bore 140 and act as a secondary deblocking mechanism
much
as described above.
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It has been found in practice that the use of a piston 140 provides more
consistent deblocking than merely applying fluid pressure. If only fluid
pressure is
utilized, occasionally the fluid will escape before full deblocking is
realized. Once
the fluid finds an escape path, it becomes difficult (if at all possible) to
achieve
enough pressure to complete deblocking. The use of a piston 140 ensures a
minimum
displacement of the lens 200 away from the balance of the lens block 100
before
fluid escape becomes significant.
In practice it has been found that in most cases the piston 140 remains
adhered
to the lens 200 after deblocking from the remainder of the block 100. This can
be
advantageous as the piston provides a gripping surface smaller in diameter
than the
lens 200 which may be used to manoeuver the lens in a subsequent edging
operation.
In the case of asymmetrical lenses, lens orientation must be maintained during
edging
for the lens to be properly oriented once mounted into frames. Accordingly
some
provision should be made in the piston 140 to provide lens orientation
information.
As illustrated in Figures 14 through 16 embodiment, one or more grooves 142
and 144 may be provided in piston 140 which would interact with a suitable key
(not
illustrated) in the bore 130 to maintain orientation between the piston 140
and the
body of the lens block 102 when the piston 140 is in its retracted position.
The same
grooves 142 and 144 may then register with whatever chuck or other holding
means
is used during the edging operation.
Other alignment indicators than grooves and keys may be utilized. For
example the bore 130 and the piston 140 may be formed in an elliptical of
other non-
circular cross- section shape.
The above description is intended in an illustrative rather than a restrictive
sense. Variations to the exact apparatus and methods described may be apparent
to
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those skilled in the relevant art without departing from the spirit and scope
of the
invention as defined by the claims set out below.
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