US2441472A

US2441472A - Lens chuck

Info

Publication number: US2441472A
Application number: US689275A
Authority: US
Inventors: D Avaucourt Pierre De Vitry
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-08-08
Filing date: 1946-08-08
Publication date: 1948-05-11
Anticipated expiration: 1965-05-11

Description

Mia-Y 1948- P. DE v. DAVAUCOURT 2,441,472-

LENS CHUCK Filed Aug. 8, 1946 Va Cour) give/ f r Patented May 11, 1948 UNITED STATES PATENT OFFICE LENS CHUCK Pierre de Vitry dAvaucom-t, Bainbridge, Pa.

Application August 8, 1946, Serial No. 689,275

4 Claims. (01. 51--216) This invention relates to a lens chuck, and relates more particularly to a chuck for holding a blocked lens blank so that one surfaceof the blank may be operated upon, for example, by the grinding wheel of a generating machine or by the lap of a fine grinding or polishing machine.

In the manufacture of ophthalmic lenses, it is customary to finish completely one side of the lens blank as a ground and polished lens surface before commencing to work on the other side. The finished lens surface is then cemented by means of optical pitch or other suitable adhesive to a lens block, leaving the unfinishedside of the lens blank exposed for operating upon ,it. It is, of course, necessary that the second lens surface be produced in predetermined and accurately aligned relationship to the first lens surface. For this purpose, it is customary to block the lens with the first lens surface accurately positioned with respect to selected surfaces of the lens block, these selected lens block surfaces being subsequently employed to align the lens block in a suitable chuck. In order to obtain accurate registration with this procedure, it is necessary to use rather elaborate blocking devices and to exercise meticulous care in blocking the lens blank.

According to the present invention, 1 provide a chuck for holding a conventional lens block in such manner that the position of the lens block .in the chuck is determined not with reference to selected surfaces of the lens block, but directly by the finished lens surface of the blocked lens blank. By the use of my chuck, therefore, accurate registration of the lens blank in the usual grinding, lapping and polishing machines may be obtained in a simple and direct manner. While care is still needed in the blocking step to assure correctcentering of the axis of the finished lens surface with respect to the transverse axis of the lens block, no particular attention need be paid to any slight tilting misalignment of the finished lens surface with respect to the longitudinal axis of the block, and hence the blocking operation is greatly simplifled.

The principal object of the present invention is tc. provide a simple, accurate and effective chuck for a blocked lens blank by means of which a finished lens surface may be accurately positioned with respect to the chuck irrespective of any slight tilting misalignment of the blank with respect to the lens block.

Other objects and advantages of the present invention will be apparent from the following description, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a top plan view of a chuck in accordance with the present invention, showing mounted therein a lens block carrying a, blocked lens blank;

Figure 2 is a side elevation of the same, partly in central vertical section along the line 2--2 of Figure 1; v

Figure 3 is a front end view thereof; and

Figure 4 is a detail view taken along the line 4-4 of Figure 2, with the lens block and lens blank omitted.

Referring more particularly to the drawings, the chuck l0 comprises a shank I l and a body l2 bifurcated by a central slot ii to form two opposing resilient jaws ll.

The shank i 1 serves in the usual manner for securing the chuck to the machine in connection with which it is to be used, which machine may be of any desired character. My chuck is particularly useful, however, in connection with generating machines for grinding a spherical or toric surface, either concave or convex, on a lens blank. v The shank II is shown as cylindrical, but it will be understood by those skilled in this art that it may be tapered, and that any other suitable means for securing the chuck body i2 to the intended machine may be substituted for the shank ll.

The jaws it are adapted to grip opposite sides of the bar-like shank l5 of a conventional lens block' l6 to the face of which is cemented, by means of pitch or other suitable adhesive H, a lens blank iii. The lens blank I8 is shown as having a finished convex surface 19 mounted adjacent the lens block I6, and an exposed concave surface I9 which is to be operated upon while the blank is held by the chuck Ill. The face of the lens block I6 is appropriately shaped for this type of lens. It will be understood by those skilled in this art that where the finished 'lens surface i9 is concave, a lens block would be used having a complementary shaped face.

will be understood also that, irrespective of the 20 are provided with pointed noses 22, best seen in Figures 1 and 4, adapted to engage directlythe finished surface IQ of the lens blank l8. Where a wide variety of work is to be handled, the tips of the noses 22 are preferably convexly rounded as shown, although they may be sharply pointed,

or, alternatively, these tips may be shaped to correspond exactly to the surface IQ of the lens as hereinafter described. The fingers 20 may conveniently be made of thin, flat brass strip, and the body l2 may be fiattended as indicated in Figure 3 to provide suitable foundations for mounting the fingers 20 solidly on the body l2.

A bolt 26 having a head 21 and a threaded portion 28 is employed for the purpose of drawing the resilient jaws ll together to grip the shank I of the lens block it. The bolt 28 is threaded into a threaded hole 29 in the lower leg of the bifurcated body l2 and extends freely through an aligned hole 30 in the upper leg of the body l2 in conventional manner.

As best shown in Figures 2 and 4, each of the jaws I4 is provided with a rounded clamping surface 3i and an undercut portion 32. The laws l4 thus cooperate to form a dovetail slot 33 within which the shank i5 of the lens block I6 is accommodated. The front faces 34 of the laws I are preferably concave in shape to correspond approximately to the conventional convex rear surface of the lens block [6. By reason of this construction, it will be observed that, prior to tightening the bolt 26, the lens block it is free to rock in the chuck, with the shank l5 assuming any desired tilted position within the range permitted by the dovetail slot 33. In inserting the blocked lens into the chuck, the lens blank is so positioned that its finished rear surface I! just engages the tip of each of the four locating fingers 20. The tips of the fingers 20 must all be accurately located in a. common plane, and this plane bears a predetermined relationship, usually a. perpendicular one, to the axis of the chuck I0. By employing four locating fingers constructed as shown, all of the fingers may be made to engage the finished lens surface I9 regardless of whether that surface is plano, spherical or toric and convexor concave. The lens blank is thus accurately aligned with the axis of the chuck Ill. The bolt 26 is then tightened, thus assuring that the lens blank is maintained in this accurately aligned relationship to the chuck.

Where prism is to be introduced into the lens in the known manner, it is necessary that the common plane of the tips of the locating fingers 20 be appropriately inclined with respect to the axis of the chuck, rather than perpendicular thereto as in the more usual case where no prism effect is desired. To obtain such tilting or inclination of the common plane, an adjacent pair of the fingers 20 may be made the appropriate amount longer or shorter, as the case may be, than the other pair. As will be evident to those skilled in the art, this may be accomplished either by using locating fingers 20 of appropriate lengths, or by providing shims between certain of the tips of the fingers and the finished lens surface l9, or by making the fingers 20 longitudinally adjustable with respect to the body [2 of the chuck by any suitable means (not shown) With the common plane of the tips of the locating fingers thus appropriately disposed with reference to the finished lens surface IS, the latter will be accurately positioned with respect to the axis of the chuck ill to obtain the desired amount of prism in the finished lens.

Where a considerable number of lenses having identical finished lens surface I! are to be successively operated upon in the chuck 10 with the same relationship of the surface ID to the axis of the chuck, I consider it preferable to shape the tips of the locating fingers 20 so as to be exactly complementary to the" surface Ii. Where my chuck is to be used in a generating machine, this may advantageously be accomplished by grinding the finger -tips in situ inthe generating machine by means of the usual cup grinding wheel or the like customarily used in connection .therewith. The generating machine is simply set to produce a surface identical to the surface IS, the chuck is securely mounted in the generating machine without any lens block or lens, and the generating machine is put through its usual cycle. This will result in grinding off the tips of the locating fingers so that they exactly correspond to the lens surface I9. By thus grinding the finger tips in situ in the generating machine, a high degree of accuracy may very easily be obtained. It will be noted that in this case there is short line contact between each locating finger tip and the lens surface I9, rather than point contact as where the tips are convexly rounded as above described. The same effect of having the finger tips located in a common plane is, however, obtained.

Although, in accordance with the patent statutes, .1 have thus described my invention in detail in the best form in which it is known to me, it will be evident to those skilled in the art that changes and modifications may be made without departing from the spirit of my invention. I desire to be limited, therefore, only by the scope of the appended claims.

I claim:

1. A chuck for holding a blocked lens, comprising in combination, a bifurcated chuck body each leg of which constitutes a resilient chuck Jaw, means for compressing said legs together to cause said jaws to clamp opposite sides of the bar-like shank of a lens block, said Jaws being provided with rounded shank-engaging surfaces and with undercut portions forming a dovetail slot, whereby said shank may be rocked in said slot into a desired position prior to clamping thereof, and four locating fingers mounted two on each leg of said chuck body in diametrically opposed pairs and having tips adapted to engage the rear surface of a lens blank cemented to said lens block.

2. 'A chuck for holding a blocked lens adhesively secured to a lens block preparatory to abrading a surface of the lens opposite the surface which is adhered to the block comprising, in combination, a chuck body including a pair of movable laws, shank engaging surfaces on said jaws engageable with the shank of a lens block disposed between the said jaws to clamp said lens block into a desired position within a substantial rocking range, means for compressing said jaws together to clamp said shank, and locating fingers rigidly mounted on said chuck body and having tips adapted to engage the surface of a lens blank cemented to said lens block holder opposite to the surface to be abraded.

3. A chuck for holding a blocked lens adhesively secured to a lens block preparatory to abrading a, surface of the lens opposite the surface which is adhered to the block comprising, in combination, a chuck body including a clamp for holding the shank of a lens block, shank engaging surfaces on said clamp constructed and arranged to clamp said shank into a desired position within a substantial rocking range, and aligning means terminating in a substantially common plane carried by and rigidly tired to said chuck body adapted to engage a surface or the lens blank cemented to said lens block opposite to the surface to be abraded to align said blank with respect to said chuck irrespective oi any slight tilting misalignment of the lens blank with respect to the lens block.

4. A chuck for holding a blocked lens adhesively secured to a lens block preparatory to abrading a surface or the lens opposite the surface which is adhered to the block comprising, in combination, a bifurcated chuck body. each leg of which constitutes a resilient chuck Jaw, means for compressing said legs together to cause said jaws to clamp opposite sides of the shank of a lens block, shank engaging surfaces on said jaws so constructed and arranged as to engage said shank in a desired position within a substantial rockins range, and four locating fingers rigidly mountgo ed on said chuck in diametrically opposed pairs and having tips terminating in a common plane adapted to engage the surface of a Iens blank cemented to said lens block holder opposite the surface to be abraded to align said blank with 5 respect to said chuck irrespective of any slight tilting misalignment of the lens blank with respect to the lens block.

PIERRE DI VITRY DAVAUCOURT.

10 REFERENCES CITED The following references are oi record in the iile of this patent:

, UNITED STATES PATENTS 15 Number Name Date 1,202,013 Ainsley Oct. 24, 1916 1,494,333 Bausch May 20, 1924 1,727,889 McCabe Sept. 10, 1929 2,253,954 Goddu Aug. 26, 1941 2,381,573 Canning Aug. 7, 1945 2,398,790

Holman Apr. 23, 1946