US1260872A - Machine for grinding compound lenses. - Google Patents

Description

H. CLEMENT.

MACHINE FOR GRINDING COMPOUND LENSES.

APPLICATION FILED MAY 2, 1914- 4 Patented Mar.26,1918.

I I I l I I I Q 0 0 0v m w mvento'z HANS CLEMENT, ornnwronk; 1v. ijassisnon fro ennnaan OPTICAL COMPANY, mo,

. A CORPORATION or new YORK.

MACHI E For, GRINDING'GOMPOUNI) LnNsns.

To all toltom'it may concern: V e .Beit known that Lllans CLEMENT, a

citizen 'ofqthe United S tates,'res'iding atNew York city, ;;iinfthejboroughyof Bronx and State of New York, have invented certain new and useful'lfmprovements inMachlnes for Grinding Compound Lenses, of which the following is afnll clear and exact description. s v a v This invention relates to niachlnes for grinding'cylindrical lenses. Lenses of this Character are ground WltlliOOlS having a 1 surface which] is. the complement in curvatureto'the surface to'be ground, the axis or the surface of :the tool being malntalned in strict parallelism with, the axis of, the surface'which isto be ground upon the lens blankji The object of the invention is to provide amachine of this character in which the supporting member for the lens blank or the tool is so constructed that the part which it supports moves in a curved path, the curvature of which approximates the curvature of the surface to be groundion the lens blank,

,whereby the pressure exerted-to hold the lens blankand tool in rubbing contact is not alone depended upon to cause these parts to have relative motion in a path corresponding to the curvatureof the surface to be ground.

'Another object of the invention is to provide a machine in which the sweep of the movable member is limited and the lens blank cannot, its relative movement, with respect to the tool, be moved to a position in which it will be entirely disengaged from the grindin tool, for if this is permitted to occur, the e ge of the lens blank frequently becomes chipped or broken.

Another object of the invention is to pro vicle a machine in which the positions of the lens blank and tool. may be interchanged whereby either convex or concave cylindrical lenses may be ground by substantially the same oscillatory movement of the movable parts of the machine.

combinations which willbe apparent to one skilled in the art from the detailed descrip- "tion hereinafter to follow and will be particularly pointed out in the appended claims. In the accompanying drawings,

Figure 1' is' a vertical. sectional view spdificefion fitters atent. Patented Mar. 26,1918. A neationfiieam a1914. arma ent. I

through machine embodying the features of myinvention; i

Fig. 2 is asimilar section taken at right angles to. the view shown in Fig. 1; and f Fig- 3 is adetail showingi the grinding tool and lens blank in reverse position to that shown in the other views. y V In the drawings, 1 and 2 respectively designate the lens blank and the grinding tool whlch are of the ordinaryconstruction used in machines of this character. The lens blank is cemented or otherwise secured tothe surface of a rectangularly shaped lens block or holder 3 which is adapted to fit into a similarly shaped opening in 'a yoke 5 in which it is secured in place by a set-screw 6, or in any other desired manner. The grinding tool 2 is provided-with a lug 7 of a similar shape and size to the lens block,

slightly tapered and'is adapted to receive spindle 12 carriedby aspherical member or ball 13. The ball 13 is provided atits upper end adjacent the bottom of the spindle '12 withan annular groove forming a seat for the lower end of the sleeve which is keyed to the spindle by means of a pin 15 projecting laterally from the lower end of the spindle, which pin engagesin a slot formed in the bottom edgeof the sleeve 10.

The spherical member or ball13 is slightly flattened at its lower end and has a centrally disposed conically tapering recess therein Qat present used, fits into the recess and rotates the tool holder and tool, (see Fig. 2).

The spherical member or ball 13 constitutes the male member. of a ball and socket joint, the female memberof which is made in twojparts 16 and 17 respectively, which are united by means of screws 18passing through abutting lugs 19. Mounted on the top annular surface of the two parts 16 and 17 is a ring 18' which is secured thereto by screws or pins 19 The ring 18 has itsinner wall beveled, as shown, which abuts againstthe outer surface of the sleeve 10 and thus serves as a stop to limit the path of the oscillatory movement of the parts 1 6 and 17 relative to the tool holder and grinding tool, and therefore maintains the lens blank,

edge of thelens blank cannot be chipped or broken, which otherwise frequently occurs when the edge of the blank strikes the edge or the grinding tool as theypasslout of engagement. 'Tie tool holder 8 is provided with a hood which serves as sane; cap to protect the upper open part of the ball and socket jointfrom the emery and glass par- 'ticles which would otherwise soon clog the joint during the grinding operation.

Projecting laterally from the parts 16 and 17, are curved arms 20 and 21, whichhave vertically disposed ends to which are secured two pairs of guide-rods 23 and 24:, the arms 20 and, 21 being preferably grooved or slotted as at 23 at diametrically opposed points, into-which grooves the lower ends of the rods are secured by screws orin any other desired way in order to obtain a substantially rigid'connectionr Projecting lat erally from the yoke 5 are arms 25, the lower ends of which arebent slightly downwardly and are adapted to fit between the upper ends of the spaced guide-rods 23 and 24c,'the rods of each pairbeing spaced just a sufficient distance apart to permit the arms 25 to slide freely up and down therebetween but to prevent anylateral movement of the same. The arms 25 are preferably circular in cross section and arranged 011 them adjacent their free ends and spaced apart a distance. equal to the distance between the l two pairs of guide-rods 23 and 24, are disk-like members 26, the outer surfaces of which are adapted to-abut the inner side faces of the guiderods 23 and 2e and areof spherical curvature, the radius of which is equal to'one-half the distance between the rods, so that arms 25 may be tiltedwithin the guide-rods and a portion of the curved surfaces of the disks will. remain in engagement with the side facesof the rods; By spacing each pair of guide-rods 23 and 24 apart just sufficient to permit the arms 25 to slidevertically up and down thereon in a determined plane and by providing the disks 26, any free independent movement of the yoke 5 and. lens holder 3 with respect to its support, except in a fixed plane isprevented, as will-be hereinafter referred] to. a The center of the ball and socket joint is preferably chosen so that the radial distance from the center of the ball andsocket jointto the surface of the grinding tool is equal] to the radius of curvature of a lens of the average cylindrical power for which the machine is designed, so that there will. be practically little or no relative movement of the arms 25 within the guide rods 23 and 24 in the grinding of a lens of a normal size.

Trunnion grooves formed in the abutting surfaces of the parts 16 and 17, and the endsof these pins pass into elongated vertical slots 29 cut in the spherical surface of the ball 13, which slots are of sufficient length to permit the parts 16 and17 to rock on the ball13 in a vertical plane passing through the pins, un-

til the ring 18 abuts againstthesleeve 10;

The pins 28 connect the supporting struc tures of the lens blank and tool holder together for synchronous rotation. The surface of the grinding tool isso ground that when positioned in the tool holder 7 its pins 28' are fitted, into alining fixed diametral line or axis ispreferably parallel to the alining longitudinal axes of the pins 28, but the fixedaxis'of the tool a may be arranged at right angles to the axis of the pins, if desired. By the construction described, the axis of the tool andof the lens blank are maintained in strict parallelism with each other, irrespective of the "direc- 7 by machinery andtakes place in a comparatively fixed plane, as will be later described.-

- The lens block 3 is provided with a-conically shaped recess 30 nto which is adapted to fit any member such as a reciprocating rod 30 through which the lens blank is given its oscillatory movement and the pressurenecessary for the grinding action is excrted'upon it. This member may be operated either manually or automatically .inaccordance with any of'the well known forms of hand surfacing machines. now on the market. v

Theoperation of the machine is as follows i-Rotation is-imparted to the entire machine by meansof the rotating shaft 12 which fitsinto the ball 13. The surface of the grinding tool iscov'ered with the necessary ,abradant material 1 such as emery or the like, and the lens blank which has.

been roughed 'to approximately thec-urvatnre of the grinding tool, and cemented to the lens block 3, is secured 'inthe' yoke 55,

which is then placed between the upper ends of the guide-rods 23and 24s., ,During the rotation ofthe machine, the lens blank is oscillated in a fixed plane by means ofthe reciprocating JarmSO and by which the necessary pressure is exerted upon'tlielens blankwfor obtaining thegrinding action.

chronism, since the oscillatory movement .As the tool and lensblank rotate in syn- 1 of the yoke'will thereforehave a minimum sliding movementwithin'the guide rods 23 and 24, which will result in an accurate is'jimparted thelens blank in practically a fixed plane, the direction of this pathof movement of the lens blank across the face of the grinding tool is continually changing.

[he pin and slot connection, however, between the portions of thejball and socket joint prevents any rotary movement of the lens blank and grinding tool in a horizontal plane so that the fixed axis of the lens and tool are always maintained in strict parallelism with each other.' Since the ball and socket joint'is arranged so that its distance from the surface or the grinding tool is equal to the radiusjof the desiredcylindrical power-of theilenslor closely approximates it, the curvature of the oscillatory paths closely conforms to the surface curvatureof the grinding tool of the lens blank and pressure which is exerted upon the lens blan s will be substantially uniform and normal to the entire surfacein contact with the surface of the grindlng" tool. The arms grinding of the lens, since the pressure with which the lens is brought into contact with the grinding tool is only depended upon to maintain these parts incorrect rotary contact. W'hen grinding lenses of the cylindrical powers, which are of greater or less radius than the distance from the surface of the grinding tool to the center of the grinding tool, the arms 25 are'free toslide in the guiderods 23 and 24:, and the lens blank is therefore free to follow the curvature of the surface of the grinding tool, but as the difference in curvature in the lenses is slight, this free movement of the lens blank independently of its supporting structure will practically be negligible and the pressure on thelens blank will remain substantially normal to the surface of the grinding tool at the points of rubbing contact between it and the lens blank. Howi ever, since arms 25 are prevented from lat cient length to prevent the lens blank from entirely passing out of engagement with the surface of the tool and will therefore prevent the edges of the lenses from being broken or chipped, which frequently occurs when this happens. i a

In the modified construction shown in Fig. 3, the positions of the lens blank 1 and grinding tool 2 are reversed or intermore perfectly changed, which is a more desirable assembly for grinding convex lenses for, as will be readily seen from the drawing, by inter changing the blank and tool in this manner, the oscillatory movement of the supporting structure will again closely conform to tliepath in which the grinding tool must move in order to grind the convex lens and therefore the free movement of the yoke 5 and the arms with respect torods 23 and 24, is reduced to a minimum, which will necessarily result in the obtaining of a more accurately ground lens. This is an importantfeature of my invention as it permits both concave and convex lenses to be groinid on thesame machine while the parts of the machine are actuated in substantially the same manner resulting in obtaining ground lenses. a

l. Ina lensfgrinding machine, two holders oneadapted to support a lens blank and the otherto carry a grinding tool, a frame having a universal joint connection with one of said holders, means for loosely mounting the other of said-holders in said frame for movement in a fixed plane, and means for preventing relative movement between said frame and its holder in a fixed plane.

2. In a lens grinding .machine of the character described, two holders one for a lens blank and the other for a grinding tool, a yoke having laterally extending arms secured to one of said holders, a support for said yoke into which the ends of said arms fit, a support for the other holder, a ball and socket joint between said supports, and means for preventing relative rotation of the supports in fixed plane.

3. In a lens grinding machine of the character described, two holders one for a lens blank and the other for a grinding tool, a support for one of said holders permitting free movement of said holder in a determined plane, a support for the other of said holders and a universal joint connection betweenrsaid supports, and means for preventing relative rotary movement of said supports in a fixed plane.

4. In a lens grinding machine of the char acter descrlbed, two'holders one for a lens blank and the other for a grinding tool, a

support for one of said holders in which said holder is freely mounted for movement in a determined plane, a support for the other of said holders in which said holder is rigidly mounted, means including a universal joint connection for connecting said supports, and means for preventing relative rotary movement of said supports in a fixed plane. a

5. In a machine of the character described, two holders one for a lens blank and the other for a grinding tool, a yoke rigidly secured to one of saidholders having laterally extending arms, a support tor $2116 1 yoke con'iprising bifurcated arn'isinto,

which the ends of saidlaterally extending arms of said yoke fit, a support for the other of said holders, and a ball and socket joint connection betweensaid supports;

6. In a lens grinding machine of the character described, a holder for a lens blank or: a grinding tool, a yoke adapted to be rigidly secured to said holder, said yoke having arms 1 extending laterally therefrom, a support for said yoke comprising bifurcated arms into which the ends of said arms slidingly fit, and'means for preventing movement of said yoke in a direction parallel to its lmigitndinal axis.

7. In a lens grinding machine of the character described, a, holder for a lens blank or a grinding tool, a yoke adaptedto be rigidly secured to said holder, said yoke having arms extending laterally therefrom, a supcopleaof this patent'may be obtained for port having bifurcated guide-arms between which the ends of said yoke arms slidingly fit, and members on said yoke arms for preventing n'ioveinent 01" said yoke in a direction parallel to its longitudinal axis.

8. In a grinding machine of the character described, a'ho'lder for a lens blank or a grinding tool, a yoke adapted to be rlgldly secured to said holder, said yoke, having arms extending laterally therefrom asupport for said yoke comprising guide-arms between Which-said yoke arms slidingly fit five cents eaclnby addressing thev Commissioner of Patents,

Washington, D. 0.?

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