US 2465153 A
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Description (OCR text may contain errors)
March 22, 1949.- F, G, FH ZSCHE 2,465,153
APPARATUS FOR BLOCKING OPTICAL LENS BLANKS Filed March 24, 1947 65 r- I, W 63 69 [NVENTOR n; i flew 6. FE/TZSCHE Patented Mar. 22, 1949 OFFICE APPARATUS FOR BLOCKING OPTICAL LENS BLANKS Fred G. Fritzsche, Milwaukee, Wis.
Application March 24, 1947, Serial No. 736,663
The present invention relates in general to improvements in the art of blocking lens blanks preparatory to final grinding of the lenses, and relates more specifically to improved apparatus fr mounting optical lens blanks upon supports to firmly hold the blanks while subsequent grinding is being effected.
Theprincipal object of this invention is to provide an improved system for blocking lens blanks in order to insure greatest possible accuracy in subsequent grinding of the blanks and polishing of the lenses.
It has heretofore been customary in the manufacture of optical lenses, to initially produce standard lens blanks with final convex curvature on one side and with arbitrary concave curvature on the opposite side thereof. Whenever one of these standard blanks was to be ground, it was blocked or attached to a recessed circular holding block with the aid of a layer of pitch interposed between the convex surface of the blank and the block recess, and with the blank in contact with the sharp peripheral edge of the block surrounding the recess. In accordance with previous commercial practice, each mounting block was placed upon a horizontal support with its cup-shaped recess upwardly exposed, after which the recess was filled with hot fluent pitch and the convex face of the lens blank was applied to the molten pitch and pressed downwardly until the blank contacted the peripheral ridge of the blank, the blank being held thus until the pitch hardened. The excess fiuent pitch was expelled from the recess during the pressing operation through diametrically opposite transverse slits formed in the peripheral ridge of the block, and would run down the adjacent sides of the mounting block; and this excess material was scraped oil after the pitch confined within the recess had hardened sufllciently to hold the lens blank in place.
This mode of removing excess pitch was not only extremely messy and wasteful. but it would also permit air pockets to form within the pitch laden recesses of the mounting blocks, and this entrapped air would frequently diminish the holding eifect of the hardened pitchto such an extent that the lens blanks would fall oil? or become loose during the grinding operation. Then too, it often happened that the workmen would not press the lens'blanks solidly against all portions of the block ridges, thus resulting in the production of imperfect and inaccurate final lenses. has been found that actual contact between the In addition to these dimculties, it-
7 Claims. (Cl. 51-277) lens blanks and the mounting blocks along the metallic peripheral ridges of the latter, diminishes the bonding or holding effect of the pitch bed which shrinks slightly upon cooling and tends to tear away from the convex lens surface due to the metal to glass contact near the periphery of the blank; and that far more eifective mounting results if the pitch is caused to contact the blanks along maximum available surface and as near to the peripheries thereof as possible.
It is therefore a more specific object of my invention to provide a mode of fastening lens blanks to carrier blocks with the aid of pitch or the like, which definitely eliminates the prior waste and messy conditions and which enables convenient, firm and accurate mounting of the blanks upon the blocks.
A further specific object of this invention is to provide an improved apparatus for more firmly and accurately attaching optical lens blanks to mounting blocks with the aid of pitch and preparatory to final grinding and finishing, in an expeditious manner.
Still another specific object ofmy present in-- vention is to provide a mode of effecting firm attachment'of lens blanks to carrier blocks, by
is to provide apparatus for utilizing maximum available contact area between the lens blank and the bed of pitch for attaching the blank to a mounting block, thus insuring more durable and reliable attachment than has heretofore been possible with prior lens blocking methods.
These and other objects and advantages of the present improvement will be apparent from the following detailed description.
A clear conception of the features involved,-
and of the construction and operation of typical mechanism for carrying on commercial exploita- Fig. 3 is a part sectional enlarged and more accurately illustrated side elevation of one of my improved mounting block and supporting assemblages, showing the position assumed by a lens blank while being attached to the block;
Fig. 4 is a likewise enlarged top view of the assemblage shown in Fig. 3;
Fig. 5 is a fragmentary part section side view of the pump plunger actuating handle, showing details of construction of the guide and lock for this handle;
Fig. 6 is a fragmentary side elevation of the pivotal end mounting of the lens blank holdin arm, the view being taken looking toward the left in Fig. 1; and
Fig. 7 is a sectional view of the pitch shutoff valve associated with the pivot stem of the lens blank holding arm,
Although the invention has been shown and described as being especially advantageously applicable for blocking optical lens blanks preparatory to grinding and polishing thereof, it is not my intention to unnecessarily restrict the utility of the improved apparatus by virtue of this limited disclosure.
Referring to the drawing, the ordinary or standard optical lens blanks'9 are usually formed of glass and are of substantially uniform thickness and various diameters, bein provided on one side with a convexly curved final surface or face In of definite curvature, and on the opposite side with a concave surface orface l l of arbitrary curvature and which is ordinarily approximately parallel to the surface l0, see Figs. 1, 2 and 4. Depending upon whether the blanks 9 are to be used for the production of ordinary or bi-focal final lenses, each standard blank is provided with a pair of hair lines [2 on the concave face ll thereof. intersecting either at the true geometrical center, or at an eccentric point of the cylindrical blank. These stock lenses are furnished by the manufacturers in large quantities and various sizes, and must be accurately ground and finished along their concave surfaces II to meet various specifications and prescriptions, whereupon they are shaped to fit the final supporting frames or rims.
In order to facilitate grinding of the concave faces II of the lens blanks 9, each blank must be firmly attached to a metal mounting block H of cylindrical formation having an upper cavity or recess l5 therein surrounded by a peripheral ridge [6 provided with diametrically opposite slits or notches l1, and the bottom of each of these standard mounting blocks I4 is bounded by a fiat surface [8. The upper block recess I5 is bounded by an approximately spherical surface generated with a shorter radius than that of the convex lens blank surface I ll, so that when a blank 9 is disposed with its surface l0 facing the recess l5 and contacting the ridge IS, the blank will not contact the recess bottom and considerable space is left between the blank and the bottom of the recess I5 for the reception of pitch. The four notches I! in the ridge l6 of each block M are spaced ninety degrees apart and serve as markers cooperable with the intersecting hair lines l2 of the blanks 9 to properly position the latter upon the blocks l4 preparatory to grinding.
All of the foregoing details of construction of the mounting blocks ii are old and well known,
and as previously indicated, it was heretofore customary to completely fill the recess l5 of each individual mounting block [4 while resting upon its bottom surface IS with hot molten pitch 20 4 and to thereafter apply the convex face ll of the blank 9 to be attached, to the recess l5 and to press the blank into firm contact with the metal ridge l5 so as to expel excess pitch through the four notches II, the parts being held in this position until the pitch cooled and hardened.- This prior method not only resulted in waste of considerable pitch, but also produced insecure fastenings, and in accordance with my p present invention, I additionally provide each mounting block I with an eccentric opening 2| and with an annular indentation 22 disposed within its recess l5 directly beneath the inner edges of the radial notches l1 thereof. I also provide a number of block embracing rings 22 formed of suitable metal and each having a central bore 24 adapted to quite snugly receive the blocks l4, each ring 23 being provided with an inwardly extending lower flange 25 and with an upper overflow notch 26 and being bounded by a side wall of slightly greater height than that of the blocks l4, so that when a block I4 is positioned within a ring 23 and rests upon the flange 25 and a lense blank 9 is placed in contact with the upper ring edge as in Fig. 3, the blank will not contact the ridge 18 but will remain spaced slightly therefrom.
When utilizing my improved apparatus for attaching a standard lens blank 8 to a mounting block [4, I first oil or grease the bore 24 of one of the ring 23 and after setting the ring on a support, I drop a block ll in preheated condition within the bore 24 and against the lower flange 25 with one of the block notches H in alinement with the overflow notch 26 of the supporting ring 23, the other three notches l1 however being sealed externally by the ring bore 24. I thereafter deposit a preheated dry lens blank 9 upon the upper edge of the ring 23 with the convex surface H] of the blank facing the recess l5 and the peripheral portion of this lower blank surface resting upon the upper ring edge but spaced from the ridge l1 and annular indentation of the block I! as shown in Fig. 3. After the hair lines i2 on the upper concave surface II of the blank 9 have been brought into proper and exact alinement with the four notches ll of the mounting block l4 the blank 9 should be firmly pressed against the top edge of the ring 23, and while pressure is thus applied, hot molten pitch 20 should be gradually injected into the recess l-5 through the block opening 2|.
This pitch injection should be slowly and carefully accomplished so as to permit all air to escape from wthin the cavity or rec'ess l5 through the alned notches I1, 26 of the block I and ring 23 respectively, and should also be continued until the entire recess [5 including the indentation 22 and the annular space between the top of the ridge l6 and the adjacent peripheral portion of the surface l0 hasbeen completely filled with pitch 20 only, and the pitch becomes visible at the ring notch 26. The pitch injection may then be discontinued but the injection pressure and the downward pressure on the lens blank 8 should be maintained until after the injected pitch 20 has cooled and hardened, whereupon the attachment is complete and the blank 9 will be firmly secured to-the block I 4 through a pitch bed alone and without contacting the block directly. The block H with the blank firmly attached thereto may then be withdrawn from the ring bore 24. for transfer to the lens grinder and polisher. In this manner the successive blanks 9 may be quickly and effectively secured to mounting blocks l4 with pitch applied throughout the entire surfaces ill of the blanks, and without wasting any pitch 20 whatsoever, and after the lenses have been ground and polished, they may be quickly released from the pitch by merely immersing the assemblages in cold water or the like.
In order to facilitate rapid and-convenient exploitation of my improved mode of attachment, I have also provided improved apparatus for maintaining the pitch 20 in properly heated and fiuent condition, for holding the successive block and ring assemblages in proper position and for clamping the lens blanks 9 thereto, and for in- Jecting the molten pitch 20 into the recesses l of the successive assemblages. As illustrated in the drawing, a preferred form of the improved apparatus comprises in general, a cup-shaped pitch confining receptacle 21 having a bottom 23 subjected to heat by an ordinary electric disk heater 29; an agitator 30 confined centrally within the receptacle 21 and being operable by a crank 3| secured to its carrying shaft 32; a support 33 for the block and ring assemblages having a bar 34 and a pin 35 thereon engageable with the successive ring flanges 25 to maintain the rings 23 in horizontal position; a lens blank holding arm 31 pivotally secured to an upright stem 38 having a pitch inlet and shut-off valve 39 associated with the lower end thereof, the arm 31 being provided with a lens blank contacting projection 40; and a manually bperable pump having a cylinder 4| which may be provided with a passage 42 immersed within the pitch 20 and also having a pitch supply and outlet pipe 43 communicable past the valve 39 with the interior of thereceptacle 21 and with the openings 2| of the successive mounting blocks l4 carried by the bar 34 and pin 35, the pump cylinder 4| also having therein a plunger 44 operable by a lever 45.
The cup-shaped receptacle 21 may be insulated in any suitable manner and in order to produce a complete portable unit, this receptacle may be provided with a built-in thermometer 41 for indicating the temperature of the pitch 20, and with a control switch 43 for the electric heater 29, at the front of the assemblage as shown in Fig. 1. The front wall of the receptacle 21 may also be provided with an upwardly projecting knock-out 49 for removing the assembled mounting blocks l4 and lens blanks 9 from the successive rings 23; and a hand rest 50 for facilitating accurate positioning of the blanks 9 upon the rings 23 while resting upon the supports 34, 35,
is provided at the upper side portion of the receptacle 21. The electric heater may be connected to a suitable source of electricity by means of detachable conductors 5i, and is concealed within a lower pocket of the receptacle 23 directly beneath the'bottom 28, and the pitch agitator 30 is of the vaned or propeller type and is preferably disposed directly above the bottom 28 beneath the pitch injection pump. The agitator supporting shaft 32 is journalled for rotation within the upper support 33 and the latter provides a closure for the major portion of the pitch receptacle but is provided with a pitch supply and removal opening 52.
The upper support 33 is firmly attached to the receptacle 21, and besides carrying the bar 34 and pin 35 upon which the successive rings 23 are mountable in truly horizontal position, the support 33 also constitutes a guide for the upright stem 38 which pivotally supports the arm 31 and which has the shut-oil valve 39 associated with its lower end. The end of the arm 31 remote from the pivot stem 38 is provided with a manipulating handle 53, and this arm 31 may be swung about the stem axis from lens blank clamping or active position as shown in Figs. 1
and 2, to release or inactive position against a stop pin 54 carried by the receptacle, and is also adapted to be swung vertically about its suspension pivot 55. A compression spring 53 is interposed between the overhanging end of the arm 31 nearest the stem 38, and a lug 51 carried by the pivot stem, as shown in Fig. 6. and this spring constantly tends to swing the clamping projection 40 of the arm 31 downwardly.
The lower portion of the pivot stem 38 and with which the shut-off valve 33 is associated, is snugly but rotatably confined within the upright bore of a fixed casing 59 having aiined ports 30 communicating with the adjacent sections of the pump discharge pipe 43, and also having a trans verse port 8| communicable with the pitch basin past a strainer 62, see Figs. 2 and "I. The outlet end of the pipe 43 is provided with a fitting 83 for attaching the pipe to the support 33, and a nozzle 64 carried by the support 33 is in open communication at its lower end with the fitting 63 while its upper end projects considerably above the support 33 and is adapted to be snugly slip-fitted into the openin s 2| of the successive mounting blocks 14. When the clamping arm 39 is in active position as in Figs. 1 and 2, the valve 39 is in the position shown in Fig. 7 with the pump displacement chamber in open communication with the pitch delivery nozzle 64; but when the arm 31 is swung in a counter-clockwise direction as viewed in Fig. 1 until it engages the fixed stop pin 54, the valve 39 will be shifted so as to connect the pump displacement chamber with the interior of the reservoir 21 through the port BI and past the strainer 62, and the nozzle 64 will be cut-off from communication with the pump.
The pump cylinder 4| is firmly connected to the reservoir 21 with its bore disposed vertically, and the passage 42 is not essential and may be omitted, but may aid in permitting more rapid escape of air during initial conditioning of the unit for normal use. The medial portion of the pump actuating lever 45 is pivotally attached to the upper end of the plunger 44, while one end of this lever is fulcrumed on a bracket BS-carried by the receptacle 21 and the other end is provided with a manipulating handle 65. The lever 45 is also engaged by a helical compression spring 61 coacting therewith and with a-fixed closure plate 68 for the pitch receptacle 21, be-
tween the handle 66 and the plunger 44, and this spring 61 tends to constantly move the pump plunger 44 into uppermost position as shown in Fig. 2. An elongated arcuate guide pin 63 which is swingably suspended from another bracket 10' carried by the receptacle 21, coacts with an opening formed in the swinging end of the lever 45 as illustrated in Figs. 1 and 5, and the handle 66 is n screw threaded into the lever end and has a central pin 12 which is cooperable with the guide pin 69 to lock the lever 45 and pump plunger 44 in any desired vertical position. The handle 66 may also be provided with a transverse pin 13 co operable with a stop pin 14 carried by the lever 45 when the handle 66 is rotated, in order to prevent complete release or removal of the handle from the lever during normal use.
Although the use of the improved apparatus while carrying on my improved lens blank blocking system should be apparent from the detailed description of the blocking unit, the normal operation is as follows. The receptacle 21 should be supplied through the opening 52 with an abundance of pitch 20 which when melted extends approximately up to the level shown, and this pitch should be heated with the aid of the heater 29 and as indicated by the thermometer 41, to a temperature sufllcient to thoroughly melt the same. The molten pitchshould be well stirred with the aid of the agitator 30 and all air should be expelled from the pump displacement chamber, the outlet pipe 43, valve 39, stringer 62, fitting 63 and nipple 64, by reciprocating the plunger 44 several times, so that all of the spaces communicating with the pump will be filled with air-free molten pitch. The successive pre-heated and moisture free mounting block I4 and ring 23 assemblages may then be placed upon the fixed supporting bar 39 and pin 35 with the pitch filled nozzle 69 slip-fitted into the block opening 2|, whereupon the lens blanks 9 may be deposited upon the upper ring edges and manually clamped in place with the clamping arm 31. The pump plunger 44 may then be released and carefully manipulated with the aid of the lever 45 to gradually inject pitch 20 under pressure through the pipe 43, valve 39, fitting 63 and nozzle 64 into the recesses l5 of the successive mounting block, ring and lens blank assemblages, and this injection of pitch should in each case be continued only until pitch is visible at the alined notches ll, 26 of the block 14 and ring 23, respectively.
The injected pitch will then fill the recess l5 and the space between the block ridge i6 and the adjacent lower convex surface I ll of the blank 9 and will extend completely across the top of the block it so that no direct contact remains between the block I I and the blank 9. After each pitch injection, the arm 31 should be retained in clamping position and the pump plunger 44 should be locked in lowered position by twisting the handle 66 of .the actuating lever 45, until after the pitch 20 within the recess l5 has set or hardened. The clamping arm 31 may thereafter be lifted and swung rearwardly against the stop pin 54, thus actuating the valve 39,.and positively cutting-oil communication between the pump and the nozzle 64 but maintaining the conduits beyond the valve 39 filled with pitch, and the pump lever locking pin 12 may also be released to permit the spring 61 to raise the plunger 44 and to draw a fresh batch of pitch into the cylinder ll past the strainer 62. The completed ring, block and lens blank assemblage may then be removed and the knock-out 49 may be employed to displace the mounting block H from the ring 23, whereupon the lens blank 9 will be firmly attached to the block I4 preparatory to grinding and polishing. The successive blanks 9 may thus be most efiectively blocked, and by actuating the valve 39 with the aid of the clamping arm 31 and by also locking the pump plunger 44 in lowered position after each pitch injection, successive air-free pitch attachments are assured.
From the foregoing detailed description, it will be apparent that my present invention provides a highly effective system of blocking lens blanks with the aid of molten pitch, and also provides simple and readily manipulable apparatus for carrying on the improved mode of lens blocking in a safe and expeditious manner. The lens mounts resulting from the use of the improved apparatus are free from air bubbles and from metal to glass contact. and the attaching pitch beds also extend throughout maximum available area between the mounting blocks and lens blanks, thus insuring firm attachment and minimizing the danger of having the blanks 9 becoming detached during the subsequent grinding and polishing operations. The improvement may also be safely and conveniently exploited with the improved portable unit, and waste of pitch is entirely eliminated. The annular notch 22 enhances the holding effect and the improved apparatus is flexible in its adaptations for mounting diflerent types of lenses, and has proven highly satisfactory and successful in actual commercial use, especially in the manufacture of more perfect optical lenses.
It should be understood that it is not desired to limit this invention to the precise details of construction of the apparatus, herein shown and described, for' various modifications within the scope of the appended claims may occur to persons skilled in the art; and it is also contemplated that specific descriptive terms employed herein be given the broadest possible interpretation consistent with the disclosure.
1. Apparatus for fastening a lens blank to a mounting block having a recess for the reception of attaching pitch, which comprises, an annular wall formed to snugly receive a lens mounting block and to provide a substantially continuous rim extending a slight distance upwardly beyond the peripheral edge of the block recess, means for supporting said wall and the block therein with said rim projecting above the peripheral edge of the block recess to provide a continuous annular lens blank support spaced from the block, and means for injecting fluent pitch upwardly through the lowest portion of the bottom of the recess to fill the space between the blank and the block within said wall 2. Apparatus for fastening a lens blank to a recessed mounting black with the aid of pitch,
which comprises, a fluent pitch receptacle, a lens blank mounting block support, an arm for clamping a lens blank relative to a block resting upon said support, a pump for injecting fluent pitch from said receptacle into the space between said block and said lens blank, and a shut-off valve for cutting off the connection from said pump to said space when said arm is removed from clamping position.
3. Apparatus for fastening a lens blank to a recessed mounting block with the aid of pitch, which comprises, a fluent pitch receptacle, a lens blank mounting block support, an arm for clamping a lens blank relative to a block resting upon said support, a pump for injecting fluent pitch from said receptacle upwardly through said block into the space between said block and said lens blank, and a shut-off valve for cutting off communication between said pump and said space and for connecting the displacement chamber of the pump with the interior of said receptacle when said arm is swung laterally away from lens clamping position.
4. Apparatus for fastening a lens blank to-a recessed mounting block with the aid of pitch, which comprises, a fluent pitch receptacle, a lens blank mounting block support, a pump having a plunger for injectingfluent pitch from said receptacle into the space between said block and a lens disposed thereabove, a lever for actuating the pump plunger, a handle for manipulating said lever, and means operable by said handle for lock- 9 ing said lever and said plunger in various positions.
5. Apparatus for fastening a lens blank to a recessed mounting block with the aid of pitch, which comprises, a fluent pitch receptacle, a support for a lens blank mounting block, an arm for clamping a lens blank relative to a block resting upon said support, said arm being swingable vertically to eflect clampingaction and being horizontally removable from clamping position, a pump for injecting pitch from said receptacle into the recess of said mounting block, and means operable by the horizontal motion of said arm for shutting ofi the supply of pitch from said pump to said recess.
6. Apparatus for fastening a lens blank to a recessed mounting block with the aid of pitch, which comprises, a fluent pitch receptacle, a support for a lens blank mounting'block, an arm for clamping a lens blank relative to a block resting upon said support, said arm being swingable vertically to efiect clamping action and being horizontally removable from. clamping position, a pump for injecting pitch from said receptacle into the recess of said mounting block, means operable by the horizontal motion of said arm for shutting off the supply of pitch from said pump to said recess, and means for locking the displacement plunger of said pump against movement.
7. Apparatus for fastening a lens blank to a recessed mounting block with the aid of pitch,
which comprises, a fluent pitch receptacle, a
said pitch injecting means to said space when said lens clamping means is removed from clamping 15 position.
FRED G. FRITZSCHE.
.REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Name Date McCabe Aug. 16, 1932 Challet Apr. 9, 1918 Number McCabe Feb. 18, 1936