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Патент USA US2603927

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July 22, T95?
J. F. MGCARTHY ET AL
2,603,922
LENS BLocKm/G DEVICE
F'iled Nov. 19, 1949
,7
l
«
»»
-
,
INVEN-roRs
ATTORNEY
Patented July 22, 1952
UNITED
2,603,922 ‘
IAT-.Es PATENT fofFfFfIc-E
.tionoiiNew York
:'6 Gleim»
1 .
:'.Thisjnventíon:relates¿te lensibloekirlg .devices
andzhas Particular referencefto'improvedfmeans
foruhloekingfophthalmicllenses.
ingtheggripped .lens blank to „theheld ¿blocker
vice
ually.versa
aligned,After
ther .the
operator.
_. lens .blank
coats .the
.has¿block
...been with
.
molten pitch, and _then manipulates„the.._swing».-.
¿In 'the conventionalmanufacture of»..ophthalmic lenses, azlensrblank ofzmoldedçglass,is-ground
andipolished'on zeach :.of; itsi two .sidesto carefully
controlled _curved surfaces#the;- shapes andïspa
ing means `.to bring «the », blank, and.»the.„block.to-„
gather... These ymaybe.called transfer-.type blockf.
ingldevißes, and, although theyeareiwidelynsed,
tial :relation :of the ~. two f_curvedfsurfaces' :result
they are: subáeot .110 en number .of disadvantages.
ingin thenptical refraction desired. ».Inthe var
,The blocking device of rthe_present..i1'n¿enfçi<;}n
ious ..1gr'rndingi~and ~polishing¢operatì9ns ato f-Which 10 isl simple, „eompach inexpensive «and leaSy «m11
the.v blank; is subjected... iti» is _ customary :to fsecure
the-rblank'~vby: means :_ of ¿an'gadhesive,.rsuohrns; .m01
erate. By the use of indicia onitheîheadinfethe
lens `¿block , and ,transparent ."pitch.> all: ftnansíer
tenpìtcnf-to; a' lenszblock swhìehf-ser'ves ars-.afhan
mechanism .is seliminated,~ and the .visual .align
dle ;.or,- couplingrmeans :byzwhich ïrthe .blank inlay
ing vis, ‘done . .directly - im tlille „block itself, . _. Means
be held and-¿controlled .This-operation islcalled 15 are provided 4for _excludinstheepîtchr fromcentain
@blocking-P 'Lens'fblocks `usually -;eons-iSt of ,a
areas of „the -lens blank. „order „to .maintain
head, lhailingdarn-outer surfaceçsubstantially:con
e_naar...areas.for> use fas Ycal.iper-ing meinte. and .f1-Q1’
forming @to >the :surface «of the i blank :opposite tto,
otherfpurposeslto.beidescribed
. `.
.-
..
.Itis a .principal object. of _this invention»to1 Pro».
AThe .--block :is 2.0 vide aLblocking. dev-ice. of~simpleoonstruetionßthat
that.:on vwhich: it - is :desired toc-werkend farsharjrk,
_ generally fr. rectangular in 1 shape.
fixed in :positionni-n the surfacing'maehlne .by
mayreadily befkept y_free of. undesirableîpìììchgtaef.
means ¿of :the shank, :rse -fthat 'the :blocked ¿lens
cumulations.
blank fbears- a .predetermined .relation to :the rest
~
Y
. Other «objects . and advantages of
.-
ì
..
inveng
tion .will-.be apparentgfromfthefollowing descrip~
of :the machine.
-The .areal iproblem :in ëblocking arises .fin con 25 tion,. taken imconnecticn withtheaecornpanying
drawings; ínáwhich:
~
„
'
’ l ,
nectionrwith asemi-'flnished lens, which is `a
lens blank: one- surface >o’flwhich has: alreadyïbeen
lï'ífà'lnîe` Lis. .a front :_elevation., of. a „blocking-Jde.
ground :and polished. vThe semi-'finished ~lens
vice according ,to .this invention, havinginserted
therein _a _lens ...blockßcarryìng :a A.block_„d„lens
mustfbe rvaflixed f to ‘ the lens' block .with` its Ifinished
surface _against the- head lx1-1a;` known relatlonvto 30
the block, in -orderfthatf the unfinished kouterlsur.
face of .the -blank may' be:so Viirlished -asfto bear
F0r`f-this purpose. it «is vcustomary nto fmark ¿the
suitableA marking device, -preparatory to 'bloclv
ing-the'flens. 'The-marking usuallyfconsists of
aoenter dot inked on-*theßflnished surface ofethe
semi-‘finished = lens, together >with a ~ pairv of i*dots
„Figure
alone;
'
-
`
~
'
-
aplan »fvlewßfî .ih_eblooking.'
,
_ `¿liti-sure. sisY [email protected]
device. with. a. .lens , lulockslrov'v.1.1.-lelenifeì.Y
the 'desired relation ‘ to-ëthe fñrstf i'ln'ishedssurfaoe. _
finished ¿surface of ~ the -~-semi-`ñnish`ed lens -in «a
blank.:
de „ice
35
_ [email protected] @geen pen-.eri [email protected]
or vshort ilines »on l-eitlsier-»side >-o1' the -center Ldot.` 40
Figuren».
v.Referring more
.
. _;pantieularly-ito
,l
¿the` dnawings;
Y.
’Pheëcenterfdotlindicatesthe optical-centenni- the
lens, rand ‘ the --row Ãof ~ dots» indicates Mtlïxe-~cylindri~the.blockingldevicefogblockìngqnead t0 omprlses ’
caläaxis »of-‘f-the‘lens. Atmel-'king device-of-‘this
character is disclosed -in 'Lockhart “Patent
z,29o;56f's,l issued July 21, -«=1«942.V
` :The "blocking operation'¿ïpropeníollows I»the
a .body portlonçerlbase . I.- l ,
.Alle
45 portionforstopfplate»Holen
The-»besef
iecting. _-.--_vieldillely-1n.ounted`n
fmey‘eontenìen'ßlyfbefvínth
fingers
_ur-11..: :e shane-.lle
. . ,.
above-described‘imarking :ofv the [email protected]
maratea,[email protected] option, r
device. ' :The blocking 'deviceis _alsoprovíded with
means~ "for holdingr la 'lens'-block Vin „known ,. rela
bas/e Il. and .are «equally .spaced .fr_.om»..eaçn
other. andiaboutithe. central vertical.axisgoflbf' ß..
lens. j Variouslingenious 'and complicated blockf
Darts wbedescribedleter- -» The ton-plate. temen
ingdeviceszareïknown, in which: the‘blank isf‘held
be retainedin position` on the` ¿base l. I yìni'any'îçä’ll."
bïglîìpping .means which permit‘the operator to 5,0 venient mannersuchas_byboltJA.
,
adjust 'the Vblank kmanually until the . inkY marks
.The ,pins I3 _are rmOllIîlted `rfor vertical
ane A»visually Yaligned rwith indicia _on ‘ the blocking
movement „with respect tothe ,topî plate'. _. L2y .and
tion-"to these _imminenti (withmeansgfor swing 55 H . "The upperiends vof the pins I3 areprefer'aglglvjY
2,603,922
4
3.
It will be apparent that the base I i could
also be made of such oil-impregnated metal, but
the expense of this product argues against this,
square as shown, to prevent rotation of the pins,
and have their extremities chamfered vto form
sharp, straight line edges i5. The square ends of
the pins I3 fit snugly for smooth sliding move
ment in correspondingly shaped holes in the top
and it is unnecessary to do so as the base Ii will
. seldom have pitch spilled Von it and the. presence
of pitch adhering to the base l i Íwould not inter
t fere with Athe proper operation of the blocking
may bejcylindrical asv shown, and are slidably
device, as it would on the top plate I2 and the
mountedy in holes I'I in the base Il. A compres
pins I3.
sion spring I8 is coiled about each of the stemsV
A type of lens block especially suitable for use
I6, and serves to yieldingly maintain the pin I3 10
in its extreme upward position shown in'Figure 3. _ with the blocking head H3, is shown in detail in
Figures 3, _e and 5. The lens block 2li of these
To limit the upward movement ofthe pins I3, a
stop washer I9 is mounted'on each pin abutting ` ‘ñgures comprises ahead 22 and a shank 25. As
against the shoulder formed between its square" Will be understood by those skilled in the art,
the upper lsurface 26 ofthe head 2li is shaped to
upper end and its cylindrical lower end, andy is
conform to the surface or" a particular semi
retained in that abutting position b_y a Ysnap
iinished VlensY blank, _a variety of lens blocks
washer 20 ñtting in a groove 2| on the'ste'm I6 in
being employed to take care Vof diiîerent kinds
conventional manner.
'
of lens blanks. Sincethe conventional semi
The top plate I2 is provided with a transverse
ophthalmic lens blank is 50 mm. in di
groove.or.__sl_ot Y22, preferably formed by milling 20 ñnished
ameter, the head 2t may convenientlybe made
for accuracy',_„,ofl such width as tcjjust accommo
of tîríisïdiameter,` although,A obviously, it may
date sn'uglyjtl'ie` Shanks ofthe lens .blocks to'be
be of any desired size. The'shank 25 is generally
useduin connection with: the blocking .head I ii.
rectangular in shape, and >is of such Widthas
'Iîheslot 22_ is aligned with two of the pins I 3, and
to fit easilybut ‘snugly in the Vslot v22 of the
cooperates .'withrthe pins to center a lens blockin
plate I2,“, The_lcwer ends orstems le of pins I3
blocking head lil, 'so-that the’lens block 23 may
serted inV the?head,.sc_.thatgthe central vertical
axisof the lens block' is aligned _with the- central
vertical axis of thegblockingnhead IG, The pins
.
be‘placed in the blocking/head I0 in .only- .one of
I3v serve also ¿to-‘exclude pitch from >the under
The'lens block 23 is provided-'with three hard-.
Surfaceiof; _the blocked. lens mank,
therein and pressed intoV shank- 25. "Foev inserts
ened steel inserts 21 having .g conical recesses
as will be de- .
scribed-hereinafter,
2l' facilitate the use of the block 23 in'connec
Iv„According to this‘invention, the top' platefIvZ
tion vwith oscillating grinding. or. polishingfma
andV the pins. I3 aremade of cil-impregnated,
porousmeht'al such as 'that soldlnunder the'_trade}
chines-such as described in United States Patents
- markj‘OilitcPf V'Such porous metal parts are made
` As thus 'far`»,described„ztheflens block :23j is
bwa-process involving‘nvelr'riajor steps. First,
conventionalv exceptV for» its rather large; di
powdered metals, forgexainple, powdered copper
ameter.' ` 'In'addition, theflens block 23 .is pro
and >powdered, tin,‘_~are; mixed in the desiredv pro
portions. y Second, thepowdered metal compound , f vided with milled cross-lines `zii and 22, inter
seating at right. anglesv at -`the central vertical
`axis“ ofthelens- block 23, and with four sub
YstantiallyY rectangular recesses 353 at its :periph
is-compressed to the desired shape and size inY a
briquetting die.
Third,V a sintering heat treat
ment >transforms the fragile briquet into. strong,
.porous metal. Fourth, lthe part is sized .by press-Y
~ inerte-_missed dimensions'in @sizing día Fifth,
the porous metal part vis 'imr'gregnated4 withnon
gumming lubricating oil by immersion in_,aj bath
ery-which are aligned with the cross lines and
are adapted to receivethe pins I3 :of the block
inghead I0'. The cross line 28is disposed verti
45 cally above the longitudinal ¿axis ofi thershank
§25, andV is.- preferably made vlonger thanjthe ¿cross
vof oil-„Atheporous metal absorbing the oil by capil
line 29't'o'visually indicateA the- 'location of .the
shank to an operator lookingdown on' the top of
_ lary‘actionfjust asralspongeïabsorbs water. Y
“We have found that molten pitch such as is Vused
the'lens'block 23, thus facilitatingl the insertion
inïb’lockingophthalmic lenses, willl not adhere,
of the lens block in the blocking head IS.
In'using »the Vblocking head - mythe operator
upon cooling, to parts made from oil-impregnated,
porous metal of the ~,character just described. Ac‘
cordingly; bym‘aking lthe parts ofour blocking
is provided withLa semi-ñnished -lens blank such
'as the lens blank SI shown in Figure '1, suitably
device that are exposed to contact " with. molten
marked as above described, and a matching lens
block 23. These are first warmed on hot plates
pitch lof this porous ‘VmetalQour "blocking device
may easily be kept -cleanjand clogging of the free
ñoating pins I3 is prevented. Any Ymolten pitch
that may accidentally come in vcontract with the
tópfplate I2 and pins AI3 may be removedwith-V
out diñ‘lculty, the oil present in the metal ¿prevent
ingl adherence `of thepitclr‘tofthe metalïpart. '
Contactwith molten' pitchtends to remove the Oil
to- appropriate temperatures _in the customary
` 'mannen -The operator then picks up'the lens
block 23, holds it so thatits- line 28 is .in ’align
, ment with the Vslot 22,"- and inserts it in the block
-‘ ing head.;l The _pins I3 then ¿project up «through
-therecesses 30 inthe lens block, andl cooperate
with the, slot 22 as above Vdescribed to center
theilens block- 23v with respectpto the blocking
frornthe `metal parts, and _it istherefore necesi'
sary; from time totime, to replace >the oil;V This
may readily be done by cleaning Lthe parts,.apply-y
ingrtoÍthe'm apliberal coating of a suitable non
gumiriing- lubricating` oil, suchï as' SAE 20 motor
oil; and ’allowing this coating to »remain on over
night. After continued use, such overnight soak
ing with oil may not suiiìce to replace the lost oil.
in which case the top plate l2 and the pins I3 may
be completely recharged with oil by dis-as~
sembling the device and soaking the top plate and
the _pinsin abath of such oil at 140° F. ‘for half an ,
hour;
" "
`
»
-.
I 6. 'I‘he operator thenV rpours ar small
quantityhof molten transparent pitch onl theup- '
head
per surface 26 of the‘lens block, the operator
readily becoming sufliciently- skilled to `employ
a'quantity of the molten pitch which is` just` suffi
cientto substantially cover- the lens block when
thalens .is pressed downfon the molten pitch.
Thepperator then picks _up the marked lens
blank> 3|, and holds it .over the, lens block. -By
looking directly downv on the assembly, the oper
ator may readily visually align the ink marks
on the blank 3’I with'the Vcross lines 28 and 29 .
fiaeosgeez
¿5
f
'çcIi"flIî-lie.-‘blcck. A’LWluéznÉth'eecper:iterßobservesfthat
Äisitotíhave fprisxñ, `fthe.ï'fp-rismifmay :be îintnoduced
by suitable adjustment of the suniiaciiig'ämachine
fthe-'Center Vdet offf'theslen‘s blank'iis'iali'gïnedwwith
fthe intersection lofi the.' cross vlines28»iand::2d-'clarin
whichitheîëblockedälensblank `
ï-the lens?-blankeaxis' is ali‘gnedÃ-with ithetcrossili'ne
Semi-’ließ presses'rithe -lens' "blank L23 IlA dowx'nlomfme
Imolten;pitcïm, and, holdsf-theî‘lens blankiin...tliat
position ;;:unti1..;~the pitch, coolssandîfharrlensifzto
`
eß'mount
ed With' omelftylpcs of isurfaci- machines,
r'he‘JI/’evier‘, it' l.isi neces'sary-tcy 'introduce the desired
¿amount-erhmmm mccnnectioniwith' tneïbiocking
operation. " Tli‘iîszïm-aylbeaccomplished by "using
"fo'rïmëa ‘bond :between :the ¿l lens i. blank :andctl'ile
' curi blockingliheadïtogether A with » :afftransfe-r» »ty-pe
~b`lo'c`k,;asl îindicated »atlf32-Sinìî’igure'ïl. ‘ . The
iblocked‘L-’lens and. lens‘lbliockv mayv then :be :re- ì
rmoved :from4 *the i' blocking fhea‘d m : for ifm-.ther
operations in the appropriate surfacingëmachine.
f0f2lbloekling ‘devic'el'su'ch aiscal-bove-iclescrîbed.v
¿The «pi-tchefree ¿ar-eas." on he under ¿surface 'of
the lens'blank 3 If are «useful =asfcaìl-iperingf «poi-nts
'tddeïtermine lens thickness during processing‘of
1; :When ¿the . operator-„gently `pir-:sseszthe lens
«the *blocked lens 1 i-n L1'surfacing machines. ¿Edge
fblankißl ; down'. on :the îrlensablcckìûâ .fas ¿iabove
calipering l-i‘s`>generally preferred, but Avcertain types
described; :thea-sharpvupper edges ‘I .5210i '.-theipins
of surfacing machines are so designed-faste re
iI-’Á'ßengageithie f under :surfaces fof a the fslensfrblank
.lbeiïor-e‘iíthetfblank »,«f contacts :the amolten'spitch, _ and
*fqu'i-re; calipering ?atç‘the center-` of f the »lens :blank
through la centrali @hole ‘provided >inthelensl block.
Í011-17bleek-ing 'head ¿mair `readily ïzbe adapted 'for
-~the ‘eo'ntinuejd ‘downward- -‘ num-:mentA iof?fthe'lens
blank as the blank is firmly seated«'onrthezblock,
:user
carries :thefyieldingminsIS down with it. The
sharpI-edges d5 .thus lcontinuously engage the
under surface of. the _lens blank during the
blocking operation, and-'preventy the pitch from
.flowing on to the --areas ofthe-lensblank .under
central,Í
v
VVAfuric'tioning'‘similarly to the‘iingers fïI‘3; to ¿keep
a‘ce'ritr'al- pot o the‘ï'under-surface of Vthe-'lens
`-1bl-ankf=1fre`effromïpitch.»
'-"’-¿ ^
surface lthat are co-extensive_~.with .the 'recess .
l»
`~
~`-
" ’ '
' " tch-free" `.rea produced-’by‘thej-pins lf3
"lcc'aïtédas tepermit the-fuse offtheï'blocked
30. The 4incite-n.pitch onthesurface 26 ñows
around ~the pins I'3 to the edge of'theblock head
' -chuek's off-theïtype liavingfour'regis
’ :t ringffpinsïlocatedj 'at ï _opposite -ends* of lcrossed
24, and. if too much pitchis. used, the excess may
¿diameters offithe- chuck: i l The registeringïpins‘of
'dropfonto fthe-.top..plate .l 211211; :has beenifound
.that >`pins lprovidedwithstraight line, sharp . up
fper. edges 11.5.. as. illustrated i in‘ìFi’gfure .3, »íiivilll'ê'suc
30
'suchL chucks requireftheßunder >surface of -the
blank at the four points ati/Which vthey engage,
'tdfbef’free `from:pitch'v‘and _other accumulations,l in
forder '_vtcffm’aintain v»accuracy «of 'registration l"of
cessful'ly;ìexelude_pitch from
»areas abovelfd'e
scri‘be‘cl .when vnsedwith flenssiblanks the Vlinder
‘the'bl'o'cked lens :inthey chuck. y-Ourblocking‘head
surfaces of which vary from plano to plus or
is therefore especially useful for blocking lenses
minus 16. diopters. This is sufficient to accom
f to be mounted in such chucks.
modate the blanks normally found in practice.
It will be observed that our blocking head,
For extreme sizes of lens blanks, the upper edges
when used with transparent pitch as above de
I5 of pins I3 could of course be shaped to cor
scribed, reduces blocking Vpractically vto the bare
respond to the blanks.
essential of visually aligning the marked lens
It has been found that Very little pitch ad 40 blank with indicia on the lens block. Since a
heres to the top plate l2 and pins I3 when they
comparable visual alignment is Anecessary even
are made of oil-impregnated, porous metal.
with the much more complicated transfer type
What little pitch does adhere to these parts may '
be easily and completely broken away by the
operator’s ñngers as soon as the blocked lens and
lens block have been removed from the blocking
head I0.
All surfaces that may come into con
blocking device, our simple blocking'head suf
fers not at all in comparison with prior devices so
45 far as accuracy inoperation is concerned.
l
While the hereindescribed blocking device is an
illustrative embodiment of the inventionin its
preferred form, it is to be understood that the L
invention is notlimited thereto but may com-"
tact With the lens block 23 and the lens blank 3I
may therefore easily be maintained free from
minute spots of pitch which would, if present,
prehend other arrangements of v parts, details
interfere with the accuracy of the blocking head 50 and features Without departing from the spirit of
IU.
the invention. We desire to be limited, therefore,
Although the above-described lens block 23 is
only by the scope of the appended claims.
the preferred form for use with our blocking
We claim:
.
»
'
head, it Will be apparent that other forms may
1. A device for centering and axially aligning 'n `
55
successfully be used. Shank 25 may be formed
a lens blank on a lens block supported in the
in any desired irregular shape so long as the
device While securing the blank to the block with
slot 22 is shaped to conform with it. Although
molten adhesive deposited on the lens block,
desirable, the recesses 30 are not essential, and,
comprising a block-receiving portion, and means
in lieu thereof, the lens block may have a cir 60 associated with said block-receiving portion for
cular periphery such as to ñt Within the pins>
centering the block With respect to the device,
I3, as indicated by the broken line 33 in Figures
said portion and said means being made of
A4 and 5.
sintered porous metal and being impregnated
The above-described operation requires the
with oil so as to be easily cleaned of Said adhesive.
use of transparent pitch, but our blocking head 65
2. A device for centering and axially aligning
may be used, if desired, with ordinary opaque
av lens blank on a lens block while securing the
pitch. In that case, a conventional transfer type
blank to the block with molten adhesive deposited
of blocking device may be used in connection with
on the lens block, comprising a block-receiving
our blocking head to obtain the necessary align
portion and a finger-like member slidably and
ment of the lens blank with respect to the lens 70 resiliently mounted therein vand adapted to pro
block held in the blocking head.
ject past the lens block> to yieldingly contact and
In the above-described blocking operation, no
mask from said adhesive a portion of the under
provisionhas been made for introducing prism
surface of the lens blank to be secured to the
into the blocked lens blank. This is not necessary
block, said block-receiving portion and member
in many cases, as even Where the ñnished lens 75 being made of sintered porous metal and being
2,603,923 ~
:members slidably:mountedY in said baseyspring
impregnated `with» 'oil` selvas; to l'be easily 1 cleaned Y
of
said'adhesive.È
Y
'
1;.
»M
„
means> for» normally >projecting the finger-like Y f
I
,members vabove said: base, `«said members 'being
<3. A. device VAforl centering -andzíaxially .aligning
yso located. as to engagethe periphery of a lens
~ aliens blank';on Ya lens blockïwhile securing the
‘ blank» to the-.block with molten adhesive deposited
on thegf lens >`block, f comprising a block-receiving
block in'sertediin thev 'device togcenter -the block
with `respect to the device, and said members
beingof such'length as to extend beyond the
thus-centered lens block and yieldingly contact
",_portion and?lnger-likevmembers slidably and
resiliently mounted therein and adapted-to pro
_ject past, the lens block toyieldingly contact and
the >underfsurface of- a lens blank centered on
mask fromv said adhesive portions of the under 10 the block to mask portions of such under’s'urface
from the adhesive used to secure the lens blank
surface ofthe »lens >blank Yto be4 secured to the
block, said block-receiving portion and members
totheblock.
6. A lens blockingY
Y -'
device
ç « as claimed ~ in'claim
'
5
being madevof- sinteredv porous metal and being
in which said upper portion of the supporting
base and said finger-like members are madefof
sintered porous 'metal and are'impregnated'with
oil, whereby any of said adhesive contacting said
, impregnated `with oil- so` as to be easily cleaned
ofv said adhesive.
~
A. p
i,
_
f ,4.1. In alens blocking device, a supporting base
having anVA upper'k portion adapted to receive a
»lens block, a. plurality of ñnger-líke members ‘
'slidably andresiliently mounted in and project
ing- ~above said base and adapted to 'extend be
upper portionand members may be-readilyre
moved therefrom.
20
‘~
l
‘
said fingers yieldingly contaçtthe vunder surface
,of a lensV blankrcentered on the block and serve
to mask portions ofv such vunder surface from ¿the
.adhesive used to secure theflens blank to the
block, and saidïblock-receiving portion and mem- Y
; Y,
>
'
HENRY T. FLUCK.
yondthe lens block and within the» margin of
" a lens blankA centered above the block, wherebyV »
‘
JAMES F. MCCARTHY¢-
‘ v,rnsr'feimsNons errno> 1
’ The following referencesa'reV of record in the
file of Vthis íp'atent: '
~
Y vI_nvrrrn .STATES PA'I‘ENTS .
bers being made of sintered porous VmetalVV and
Number ,
` being impregnated with oil so as to be easily l
Re. 18,569
„McCabe ____ _, ____ __ Aug.> 16, 1932
1,284,283
Flad __„__._____-____~__ Nov. 12, 1918
1, »Name '
.
Date
Y
cleaned of said adhesive. '
' 5. In a lens blocking device. a supportingfbase
, having an v'upper portion recessedrto receive lthe
1,556,658
Williams» ____ _'_ ____ __ Oct. 13, 1925
1,642,347
shank of a lens block, a plurality of finger-like
'2,465,153
Williams e ____ _'__v___ Sept.v 13, 192'?
Fritzsche ;___'___'____` Mar. 22, 1949 .
,
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